阅读说明：本技术 控制喷射混凝土回弹的配方 (Formula for controlling rebound of sprayed concrete ) 是由 冯晓宁 杨帆 许高赫 席康利 曹君 徐洪流 杜耀辉 高岳 周飞 张明富 王夢 于 2021-08-18 设计创作，主要内容包括：本发明公开了控制喷射混凝土回弹的配方,喷射混凝土的材料配比如下：砂石率：45％-55％,水泥掺量：424kg/m～(3)-464kg/m～(3),水灰比：0.39-0.43,外加剂种类：聚丙烯纤维、短切玄武岩纤维、超高性能合成纤维,外加剂掺量：0.08％-0.12％,包括以下步骤：步骤一：首先采用室内试验的方式对砂石比、水泥掺量、外加剂掺量、水胶比等各项数据进行控制,并记录每个影响因素的占比变化时,引起喷射混凝土回弹率,本发明通过结合现场监控量测数据与数值模拟分析研究隧道支护结构的变形机理与稳定性分析,较大程度上解决隧道超挖严重和喷射混凝土回弹损耗高的技术难题,具有极大的社会经济、生产实践、科研学术价值。(The invention discloses a formula for controlling rebound of shotcrete, which comprises the following materials in parts by weight: sand and stone ratio: 45% -55%, cement mixing amount: 424kg/m 3 ‑464kg/m 3 Water-cement ratio: 0.39-0.43, additive type: polypropylene fiber, chopped basalt fiber, ultra-high performance synthetic fiber, admixture mixing amount: 0.08% -0.12%, comprising the following steps: the method comprises the following steps: the method comprises the steps of firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor.)

1. The formula for controlling the rebound of the sprayed concrete is characterized in that: the material proportion of the sprayed concrete is as follows: sand and stone ratio: 45% -55%;

the cement mixing amount is as follows: 424kg/m3-464kg/m 3;

water-cement ratio: 0.39-0.43;

the types of the additives are as follows: polypropylene fibers, chopped basalt fibers and ultrahigh-performance synthetic fibers;

the admixture mixing amount is as follows: 0.08 to 0.12 percent.

2. The formulation for controlling shotcrete rebound according to claim 1, wherein: the method comprises the following steps:

the method comprises the following steps: firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor;

step two: analyzing the experimental data, and determining the reasonable range of each influence factor so as to control the rebound quantity of the sprayed concrete within the optimal range;

step three: carrying out specific grouping on the tests;

step four: testing to obtain the slump of the concrete under various components and the compressive strength of the concrete at the age of 7 days;

step five: analyzing the influence degree of each factor on the slump and the compressive strength of the concrete, and respectively carrying out range analysis on the slump and the compressive strength of the concrete;

step six: preparing materials required by a field test, wherein cement, river sand, gravel, water, a water reducing agent, an accelerating agent and the like are all field materials, the materials need to meet the standard requirements, and chopped basalt fibers need to be purchased;

step seven: preparing a test device on site: the device comprises a large plastic cloth for collecting rebound concrete, an electronic scale for measuring the rebound concrete, a rebound tester for measuring the concrete strength, a die of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm, a cutting machine, a press machine, a wet spraying machine, a workbench frame, a mixing station and a concrete tank truck;

step eight: the method comprises the steps of performing a shotcrete resilience control test on site, wherein a section with a length of 3m is drawn, concrete tests with different proportions are respectively adopted, resilience amounts of concrete at different positions such as an arch crown and an arch waist are recorded, and 1.88 kg-2.82 kg of fiber is added into each concrete;

step nine: determining the section of the sprayed concrete, and adding fibers in a mixing station according to different proportions;

step ten: laying plastic cloth on the ground, spraying the positions respectively, and collecting the rebounded concrete;

step eleven: weighing the collected rebound quantity, and testing the concrete strength at different positions;

step twelve: the data of the section without adding fiber is tested according to the steps, and the following tests are required to be carried out for researching the effect of the added fiber in the concrete during construction: firstly, spraying concrete into a model of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm during construction, processing the concrete into a cubic test block of 10cm multiplied by 10cm after the concrete reaches a certain strength, and curing for 28 days under standard conditions to perform a compressive strength test;

secondly, measuring the strength of the surface of the sprayed concrete by using a concrete strength resiliometer, dividing a measuring area according to the positions for measurement, wherein the measuring area is selected to be the side surface of the concrete detected by the resiliometer in the horizontal direction as far as possible, and when the requirement cannot be met, the resiliometer can be positioned on the pouring side surface, the surface or the bottom surface of the concrete detected in the non-horizontal direction;

and thirdly, the thickness of the sprayed layer can be detected by methods such as a punching or laser profiler, optical band photography and the like, each position is counted respectively, the thickness of the sprayed layer at all the positions of the inspection holes is more than 60% and not less than the designed thickness, the average thickness is not less than the designed thickness, the minimum thickness is not less than 1/2 of the designed thickness, in the weak and broken surrounding rock section, the thickness of the sprayed layer is not less than the minimum thickness specified by the design, and the thickness of the concrete sprayed by the reinforcing mesh is not less than 6 cm.

3. The formulation for controlling shotcrete rebound according to claim 2, wherein: in the second step, the sand rate, the cement mixing amount, the water cement ratio, the additive type and the additive mixing amount in the test are respectively set to three levels, and a five-factor three-level method of an orthogonal test is adopted, so that 18 groups of tests are required in total.

4. The formulation for controlling shotcrete rebound according to claim 2, wherein: and in the second step, selecting a correct orthogonal test point according to the experimental data.

5. The formulation for controlling shotcrete rebound according to claim 2, wherein: the test in the second step mainly researches the concrete slump and the concrete compressive strength under different components and proportions, optimizes and adjusts the proportion of the sprayed concrete components and the content of the added fiber, and provides the rebound mechanism of the added fiber sprayed concrete and the optimal material proportion of the indoor test.

6. The formulation for controlling shotcrete rebound according to claim 2, wherein: in the third step, the test is carried out according to the test method of mechanical properties of common concrete, the slump of each group is firstly measured, then a sample of 100 multiplied by 100mm is prepared, and the compressive strength of the concrete test blocks in the age of 7d, 14d and 28d is measured.

7. The formulation for controlling shotcrete rebound according to claim 2, wherein: in the fourth step, three concrete test blocks are manufactured in each group according to the standard requirements, and the average value of the three test blocks is obtained by measuring the compressive strength of the three test blocks.

8. The formulation for controlling shotcrete rebound according to claim 2, wherein: in the fifth step, the influence degree of each factor on the concrete slump obtained through the table is as follows: the water cement ratio, the admixture doping amount, the admixture type, the sand rate and the cement doping amount are larger than each other, for the concrete compressive strength of 7 days, the influence degree of each factor is as follows, the admixture type, the admixture doping amount, the cement doping amount, the sand rate and the water cement ratio is larger than each other, the influence of the water cement ratio on the slump constant is largest, the influence on the compressive strength of the concrete is smallest, and the influence of the added fibers on the compressive strength of the concrete is largest.

9. The formulation for controlling shotcrete rebound according to claim 2, wherein: and in the fifth step, the inverse relation between the slump of the concrete and the water-cement ratio is obtained through a table, the larger the water-cement ratio is, the smaller the slump is, and the total slump is within the range of 106-114 mm, so that the requirement of spraying the concrete is met. The concrete with the age of 7 days has different compression strength due to different test results of mixture ratio and added components. The 15 th group test has the highest strength which reaches 30.13MPa, and the 15 th group test mixture ratio is cement: river sand: crushing stone: water: water reducing agent: accelerator: adding fiber 1: 1.98: 1.98: 0.41: 0.01: 0.07: 0.0065, group 1, the test results are minimal, 24.76 MPa. The average value of the compressive strength of the concrete in the 7-day age is 27.28MPa, the maximum value of the compressive strength of the concrete when polypropylene fibers are added is 27.37MPa and is 0.09MPa higher than the average value, the maximum value of the compressive strength of the concrete when chopped basalt fibers are added is 30.13MPa and is 2.85MPa higher than the average value, the maximum value of the compressive strength of the concrete when ultrahigh-performance synthetic fibers are added is 28.47MPa and is 1.19MPa higher than the average value, so the effect of the added fibers is seen from the result of the compressive strength of the concrete: chopped basalt fiber > ultra-high performance synthetic fiber > polypropylene fiber.

10. The formulation for controlling shotcrete rebound according to claim 2, wherein: in the step twelve, the concrete rebound rate is calculated by weighing the total amount of rebound falling concrete on site, and the calculation formula of the rebound rate is as follows: and J is the total resilience amount/the total concrete amount, wherein the total resilience amount is weighed during site construction, and the total concrete amount is obtained by weighing and calculating before construction.

Technical Field

The invention belongs to the technical field of shotcrete resilience control, and particularly relates to a formula for controlling shotcrete resilience.

Background

In recent years, with the continuous development of national society, economy and other aspects of China, urban population is more and more concentrated, population mobility is aggravated, social and economic activities are more frequent, and updated and stricter standards are provided for the transportation industry of China. In the face of the three challenges of population growth, resource shortage and environmental deterioration, underground engineering buildings such as tunnels have incomparable advantages. Such as railway and highway tunnel engineering, urban subway and underground building engineering, mine engineering, hydropower station underground factory building and water delivery tunnel engineering, civil air defense and national air defense engineering and the like. For years, the technical problem and difficulty that the loss ratio is as high as more than 2.0 (the loss of a single hole and a single kilometer of a two-lane highway tunnel is over five million) caused by overexcavation and sprayed concrete rebound in mountain tunnel construction by a drilling and blasting method in China are solved.

At present, the existing concrete wet-spraying construction process has less means for effectively controlling the rebound rate of sprayed concrete, and the concrete is usually wasted on a construction site due to over-undermining and rebound, so that the process level of concrete wet-spraying construction is greatly influenced, and the construction cost is greatly increased.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the existing defects and provide a formula for controlling the rebound of sprayed concrete, so as to solve the problems that the existing concrete wet spraying construction process proposed in the background art rarely has means for effectively controlling the rebound rate of the sprayed concrete, and the concrete is wasted on a construction site due to over-under excavation and rebound, so that the process level of concrete wet spraying construction is greatly influenced, and the construction cost is greatly increased.

In order to achieve the purpose, the invention provides the following technical scheme: controlling the rebound formula of the sprayed concrete, wherein the material ratio of the sprayed concrete is as follows: sand and stone ratio: 45% -55%;

the cement mixing amount is as follows: 424kg/m3-464kg/m 3;

water-cement ratio: 0.39-0.43;

the types of the additives are as follows: polypropylene fibers, chopped basalt fibers and ultrahigh-performance synthetic fibers;

the admixture mixing amount is as follows: 0.08 to 0.12 percent.

The formula for controlling the rebound of the sprayed concrete comprises the following steps:

the method comprises the following steps: firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor;

step two: analyzing the experimental data, and determining the reasonable range of each influence factor so as to control the rebound quantity of the sprayed concrete within the optimal range;

step three: carrying out specific grouping on the tests;

step four: testing to obtain the slump of the concrete under various components and the compressive strength of the concrete at the age of 7 days;

step five: analyzing the influence degree of each factor on the slump and the compressive strength of the concrete, and respectively carrying out range analysis on the slump and the compressive strength of the concrete;

step six: preparing materials required by a field test, wherein cement, river sand, gravel, water, a water reducing agent, an accelerating agent and the like are all field materials, the materials need to meet the standard requirements, and chopped basalt fibers need to be purchased;

step seven: preparing a test device on site: the device comprises a large plastic cloth for collecting rebound concrete, an electronic scale for measuring the rebound concrete, a rebound tester for measuring the concrete strength, a die of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm, a cutting machine, a press machine, a wet spraying machine, a workbench frame, a mixing station and a concrete tank truck;

step eight: the method comprises the steps of performing a shotcrete resilience control test on site, wherein a section with a length of 3m is drawn, concrete tests with different proportions are respectively adopted, resilience amounts of concrete at different positions such as an arch crown and an arch waist are recorded, and 1.88 kg-2.82 kg of fiber is added into each concrete;

step nine: determining the section of the sprayed concrete, and adding fibers in a mixing station according to different proportions;

step ten: laying plastic cloth on the ground, spraying the positions respectively, and collecting the rebounded concrete;

step eleven: weighing the collected rebound quantity, and testing the concrete strength at different positions;

step twelve: the data of the section without adding fiber is tested according to the steps, and the following tests are required to be carried out for researching the effect of the added fiber in the concrete during construction: firstly, spraying concrete into a model of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm during construction, processing the concrete into a cubic test block of 10cm multiplied by 10cm after the concrete reaches a certain strength, and curing for 28 days under standard conditions to perform a compressive strength test;

secondly, measuring the strength of the surface of the sprayed concrete by using a concrete strength resiliometer, dividing a measuring area according to the positions for measurement, wherein the measuring area is selected to be the side surface of the concrete detected by the resiliometer in the horizontal direction as far as possible, and when the requirement cannot be met, the resiliometer can be positioned on the pouring side surface, the surface or the bottom surface of the concrete detected in the non-horizontal direction;

and thirdly, the thickness of the sprayed layer can be detected by methods such as a punching or laser profiler, optical band photography and the like, each position is counted respectively, the thickness of the sprayed layer at all the positions of the inspection holes is more than 60% and not less than the designed thickness, the average thickness is not less than the designed thickness, the minimum thickness is not less than 1/2 of the designed thickness, in the weak and broken surrounding rock section, the thickness of the sprayed layer is not less than the minimum thickness specified by the design, and the thickness of the concrete sprayed by the reinforcing mesh is not less than 6 cm.

Preferably, in the second step, the sand rate, the cement mixing amount, the water-cement ratio, the additive type and the additive mixing amount in the test are respectively set to three levels, and a five-factor three-level method of an orthogonal test is adopted, so that 18 groups of tests are required in total;

preferably, in the second step, a correct orthogonal test point is selected according to the test data;

preferably, the test in the second step mainly researches the concrete slump and the concrete compressive strength under different components and proportions, optimizes and adjusts the proportion of the components of the sprayed concrete and the content of the added fiber, and provides a rebound mechanism of the added fiber sprayed concrete and an optimal material proportion for indoor tests.

Preferably, in the third step, the test is carried out according to the test method of mechanical properties of common concrete, the slump of each group is firstly measured, then a sample with the size of 100 multiplied by 100mm is prepared, and the compressive strength of the concrete test blocks in the age of 7d, 14d and 28d is measured.

Preferably, in the fourth step, three concrete test blocks are manufactured in each group according to the standard requirements, and the average value of the three concrete test blocks is obtained by measuring the compressive strength of the three concrete test blocks.

Preferably, in the step five, the influence degree of each factor on the concrete slump obtained by the table is as follows: the water cement ratio, the admixture doping amount, the admixture type, the sand rate and the cement doping amount are larger than each other, for the concrete compressive strength of 7 days, the influence degree of each factor is as follows, the admixture type, the admixture doping amount, the cement doping amount, the sand rate and the water cement ratio is larger than each other, the influence of the water cement ratio on the slump constant is largest, the influence on the compressive strength of the concrete is smallest, and the influence of the added fibers on the compressive strength of the concrete is largest.

Preferably, in the fifth step, the slump of the concrete is obtained through a table to be in inverse proportion to the water-cement ratio, the larger the water-cement ratio is, the smaller the slump is, and the total slump is within the range of 106-114 mm, so that the requirement of spraying the concrete is met. The concrete with the age of 7 days has different compression strength due to different test results of mixture ratio and added components. The 15 th group test has the highest strength which reaches 30.13MPa, and the 15 th group test mixture ratio is cement: river sand: crushing stone: water: water reducing agent: accelerator: adding fiber 1: 1.98: 1.98: 0.41: 0.01: 0.07: 0.0065, group 1, the test results are minimal, 24.76 MPa. The average value of the compressive strength of the concrete in the 7-day age is 27.28MPa, the maximum value of the compressive strength of the concrete when polypropylene fibers are added is 27.37MPa and is 0.09MPa higher than the average value, the maximum value of the compressive strength of the concrete when chopped basalt fibers are added is 30.13MPa and is 2.85MPa higher than the average value, the maximum value of the compressive strength of the concrete when ultrahigh-performance synthetic fibers are added is 28.47MPa and is 1.19MPa higher than the average value, so the effect of the added fibers is seen from the result of the compressive strength of the concrete: chopped basalt fiber > ultra-high performance synthetic fiber > polypropylene fiber.

Preferably, in the step twelve, the concrete rebound rate is calculated by weighing the total amount of the rebound falling concrete on site, and the calculation formula of the rebound rate is as follows: and J is the total resilience amount/the total concrete amount, wherein the total resilience amount is weighed during site construction, and the total concrete amount is obtained by weighing and calculating before construction.

Compared with the prior art, the invention provides a formula for controlling the rebound of sprayed concrete, and the formula has the following beneficial effects:

the invention researches the deformation mechanism and stability analysis of the tunnel supporting structure by combining field monitoring measurement data and numerical simulation analysis, solves the technical problems of serious tunnel overexcavation and high rebound loss of sprayed concrete to a greater extent, has great social and economic, production practice and scientific research academic values, and avoids the problems that the existing concrete wet-spraying construction process has fewer means for effectively controlling the rebound rate of the sprayed concrete, the concrete is often wasted on the construction site due to undermining and rebound, the process level of concrete wet-spraying construction is greatly influenced, and the construction cost is greatly increased.

Drawings

FIG. 1 is a sequence chart of a field test in a formulation for controlling shotcrete rebound according to the present invention;

FIG. 2 is a schematic diagram of a shotcrete test in a formulation for controlling shotcrete rebound according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

Referring to fig. 1-2, the present invention provides a technical solution: controlling the rebound formula of the sprayed concrete, wherein the material ratio of the sprayed concrete is as follows: sand and stone ratio: 45% -55%;

the cement mixing amount is as follows: 424kg/m3-464kg/m 3;

water-cement ratio: 0.39-0.43;

the types of the additives are as follows: polypropylene fibers, chopped basalt fibers and ultrahigh-performance synthetic fibers;

the admixture mixing amount is as follows: 0.08 to 0.12 percent.

The formula for controlling the rebound of the sprayed concrete comprises the following steps:

the method comprises the following steps: firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor;

step two: analyzing the experimental data, and determining the reasonable range of each influence factor so as to control the rebound quantity of the sprayed concrete within the optimal range;

step three: the experimental groupings are shown in the following table:

test No	Sand rate	Cement mixing amount kg/m3	Water cement ratio	Kind of additive	Admixture mixing amount
						1	45％	424	0.39	Polypropylene fiber	0.08％
2	45％	444	0.41	Chopped basalt fiber	0.1％
						3	45％	464	0.43	Ultra-high performance synthetic fiber	0.12％
4	50％	424	0.39	Chopped basalt fiber	0.1％
						5	50％	444	0.41	Ultra-high performance synthetic fiber	0.12％
6	50％	464	0.43	Polypropylene fiber	0.08％
						7	55％	424	0.41	Polypropylene fiber	0.12％
8	55％	444	0.43	Chopped basalt fiber	0.08％
						9	55％	464	0.39	Ultra-high performance synthetic fiber	0.1％
10	45％	424	0.43	Ultra-high performance synthetic fiber	0.1％
						11	45％	444	0.39	Polypropylene fiber	0.12％
12	45％	464	0.41	Chopped basalt fiber	0.08％
						13	50％	424	0.41	Ultra-high performance synthetic fiber	0.08％
14	50％	444	0.43	Polypropylene fiber	0.1％
						15	50％	464	0.39	Chopped basalt fiber	0.12％
16	55％	424	0.43	Chopped basalt fiber	0.12％
						17	55％	444	0.39	Ultra-high performance synthetic fiber	0.08％
18	55％	464	0.41	Polypropylene fiber	0.1％

Step four: the slump and the compressive strength of the concrete at the age of 7 days under various components are measured by the test and are shown in the following table:

step five: the influence degree of each factor on the slump and the concrete compressive strength is analyzed, the extreme difference analysis is respectively carried out on the influence degree, and the results are shown in the following table:

step six: preparing materials required by a field test, wherein cement, river sand, gravel, water, a water reducing agent, an accelerating agent and the like are all field materials, the materials need to meet the specification requirement, and chopped basalt fibers need to be purchased, and the specific purchase conditions are shown in the following table:

step seven: preparing a test device on site: the device comprises a large plastic cloth for collecting rebound concrete, an electronic scale for measuring the rebound concrete, a rebound tester for measuring the concrete strength, a die of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm, a cutting machine, a press machine, a wet spraying machine, a workbench frame, a mixing station and a concrete tank truck;

step eight: the method comprises the steps of performing a shotcrete resilience control test on site, wherein a section with a length of 3m is drawn, concrete tests with different proportions are respectively adopted, resilience amounts of concrete at different positions such as an arch crown and an arch waist are recorded, and 1.88 kg-2.82 kg of fiber is added into each concrete;

step nine: determining the section of the sprayed concrete, and adding fibers into a mixing station according to the proportion, wherein the addition amount of the fibers in each concrete is 1.88 kg;

step ten: laying plastic cloth on the ground, spraying the positions respectively, and collecting the rebounded concrete;

step eleven: weighing the collected rebound quantity, and testing the concrete strength at different positions;

step twelve: the data of the section without adding fiber is tested according to the steps, and the following tests are required to be carried out for researching the effect of the added fiber in the concrete during construction: firstly, spraying concrete into a model of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm during construction, processing the concrete into a cubic test block of 10cm multiplied by 10cm after the concrete reaches a certain strength, and curing for 28 days under standard conditions to perform a compressive strength test;

secondly, measuring the strength of the surface of the sprayed concrete by using a concrete strength resiliometer, dividing a measuring area according to the positions for measurement, wherein the measuring area is selected to be the side surface of the concrete detected by the resiliometer in the horizontal direction as far as possible, and when the requirement cannot be met, the resiliometer can be positioned on the pouring side surface, the surface or the bottom surface of the concrete detected in the non-horizontal direction;

thirdly, the thickness of the sprayed layer can be detected by methods such as punching or laser profiler, light band photography and the like, each position is counted respectively, the thickness of the sprayed layer at all the positions of the inspection holes should be more than 60% and not less than the designed thickness, the average thickness should not be less than the designed thickness, the minimum thickness should not be less than 1/2 of the designed thickness, in the weak and broken surrounding rock section, the thickness of the sprayed layer should not be less than the minimum thickness specified by the design, and the thickness of the concrete sprayed by the reinforcing mesh should not be less than 6cm

In the present invention, preferably, in the second step, the sand ratio, the cement mixing amount, the water-cement ratio, the additive type and the additive mixing amount in the test are respectively set to three levels, and a five-factor three-level method of an orthogonal test is adopted, so that 18 sets of tests are required, as shown in the following table:

in the present invention, preferably, in step two, the selection of the orthogonal test points is shown in the following table:

in the invention, preferably, the test in the step two mainly researches the concrete slump and the concrete compressive strength under different components and proportions, optimizes and adjusts the proportion of the components of the sprayed concrete and the content of the added fiber, and provides a rebound mechanism of the added fiber sprayed concrete and an optimal material proportion of the added fiber sprayed concrete in an indoor test.

In the invention, preferably, in the third step, the test is carried out according to the test method of mechanical properties of common concrete, the slump of each group is firstly measured, then 100 x 100mm samples are prepared, and the compressive strength of the concrete test blocks in the age of 7d, 14d and 28d is measured.

In the invention, preferably, in the fourth step, three concrete test blocks are manufactured in each group according to the standard requirements, and the average value of the three concrete test blocks is obtained by measuring the compressive strength of the three test blocks.

In the present invention, preferably, in the fifth step, the influence degree of each factor on the concrete slump obtained by the table is as follows: the water cement ratio, the admixture doping amount, the admixture type, the sand rate and the cement doping amount are larger than each other, for the concrete compressive strength of 7 days, the influence degree of each factor is as follows, the admixture type, the admixture doping amount, the cement doping amount, the sand rate and the water cement ratio is larger than each other, the influence of the water cement ratio on the slump constant is largest, the influence on the compressive strength of the concrete is smallest, and the influence of the added fibers on the compressive strength of the concrete is largest.

In the invention, preferably, in the step five, the slump of the concrete is obtained through a table and is in inverse proportion to the water-cement ratio, the larger the water-cement ratio is, the smaller the slump is, and the total slump is within the range of 106-114 mm, thereby meeting the requirements of sprayed concrete. The concrete with the age of 7 days has different compression strength due to different test results of mixture ratio and added components. The 15 th group test has the highest strength which reaches 30.13MPa, and the 15 th group test mixture ratio is cement: river sand: crushing stone: water: water reducing agent: accelerator: adding fiber 1: 1.98: 1.98: 0.41: 0.01: 0.07: 0.0065, group 1, the test results are minimal, 24.76 MPa. The average value of the compressive strength of the concrete in the 7-day age is 27.28MPa, the maximum value of the compressive strength of the concrete when polypropylene fibers are added is 27.37MPa and is 0.09MPa higher than the average value, the maximum value of the compressive strength of the concrete when chopped basalt fibers are added is 30.13MPa and is 2.85MPa higher than the average value, the maximum value of the compressive strength of the concrete when ultrahigh-performance synthetic fibers are added is 28.47MPa and is 1.19MPa higher than the average value, so the effect of the added fibers is seen from the result of the compressive strength of the concrete: chopped basalt fiber > ultra-high performance synthetic fiber > polypropylene fiber.

In the invention, preferably, in the step twelve, the calculation method of the concrete rebound rate is to calculate the rebound rate by weighing the total amount of the rebound falling concrete on site, and the calculation formula of the rebound rate is as follows: and J is the total resilience amount/the total concrete amount, wherein the total resilience amount is weighed during site construction, and the total concrete amount is obtained by weighing and calculating before construction.

Example two

Referring to fig. 1-2, the present invention provides a technical solution: controlling the rebound formula of the sprayed concrete, wherein the material ratio of the sprayed concrete is as follows: sand and stone ratio: 45 to 55 percent

The cement mixing amount is as follows: 424kg/m3-464kg/m3

Water-cement ratio: 0.39-0.43

The types of the additives are as follows: polypropylene fiber, chopped basalt fiber and ultrahigh-performance synthetic fiber

The admixture mixing amount is as follows: 0.08 to 0.12 percent.

The formula for controlling the rebound of the sprayed concrete comprises the following steps:

the method comprises the following steps: firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor;

step two: analyzing the experimental data, and determining the reasonable range of each influence factor so as to control the rebound quantity of the sprayed concrete within the optimal range;

step three: the experimental groupings are shown in the following table:

test No	Sand rate	Cement mixing amount kg/m3	Water cement ratio	Kind of additive	Admixture mixing amount
						1	45％	424	0.39	Polypropylene fiber	0.08％
2	45％	444	0.41	Chopped basalt fiber	0.1％
						3	45％	464	0.43	Ultra-high performance synthetic fiber	0.12％
4	50％	424	0.39	Chopped basalt fiber	0.1％
						5	50％	444	0.41	Ultra-high performance synthetic fiber	0.12％
6	50％	464	0.43	Polypropylene fiber	0.08％
						7	55％	424	0.41	Polypropylene fiber	0.12％
8	55％	444	0.43	Chopped basalt fiber	0.08％
						9	55％	464	0.39	Ultra-high performance synthetic fiber	0.1％
10	45％	424	0.43	Ultra-high performance synthetic fiber	0.1％
						11	45％	444	0.39	Polypropylene fiber	0.12％
12	45％	464	0.41	Chopped basalt fiber	0.08％
						13	50％	424	0.41	Ultra-high performance synthetic fiber	0.08％
14	50％	444	0.43	Polypropylene fiber	0.1％
						15	50％	464	0.39	Chopped basalt fiber	0.12％
16	55％	424	0.43	Chopped basalt fiber	0.12％
						17	55％	444	0.39	Ultra-high performance synthetic fiber	0.08％
18	55％	464	0.41	Polypropylene fiber	0.1％

Step four: the slump and the compressive strength of the concrete at the age of 7 days under various components are measured by the test and are shown in the following table:

step five: the influence degree of each factor on the slump and the concrete compressive strength is analyzed, the extreme difference analysis is respectively carried out on the influence degree, and the results are shown in the following table:

step six: preparing materials required by a field test, wherein cement, river sand, gravel, water, a water reducing agent, an accelerating agent and the like are all field materials, the materials need to meet the specification requirement, and chopped basalt fibers need to be purchased, and the specific purchase conditions are shown in the following table:

step seven: preparing a test device on site: the device comprises a large plastic cloth for collecting rebound concrete, an electronic scale for measuring the rebound concrete, a rebound tester for measuring the concrete strength, a die of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm, a cutting machine, a press machine, a wet spraying machine, a workbench frame, a mixing station and a concrete tank truck;

step eight: the method comprises the steps of performing a shotcrete resilience control test on site, wherein a section with a length of 3m is drawn, concrete tests with different proportions are respectively adopted, resilience amounts of concrete at different positions such as an arch crown and an arch waist are recorded, and 1.88 kg-2.82 kg of fiber is added into each concrete;

step nine: determining the section of the sprayed concrete, and adding fibers into a mixing station according to the proportion, wherein the addition amount of the fibers in each concrete is 2.35 kg;

step ten: laying plastic cloth on the ground, spraying the positions respectively, and collecting the rebounded concrete;

step eleven: weighing the collected rebound quantity, and testing the concrete strength at different positions;

step twelve: the data of the section without adding fiber is tested according to the steps, and the following tests are required to be carried out for researching the effect of the added fiber in the concrete during construction: firstly, spraying concrete into a model of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm during construction, processing the concrete into a cubic test block of 10cm multiplied by 10cm after the concrete reaches a certain strength, and curing for 28 days under standard conditions to perform a compressive strength test;

secondly, measuring the strength of the surface of the sprayed concrete by using a concrete strength resiliometer, dividing a measuring area according to the positions for measurement, wherein the measuring area is selected to be the side surface of the concrete detected by the resiliometer in the horizontal direction as far as possible, and when the requirement cannot be met, the resiliometer can be positioned on the pouring side surface, the surface or the bottom surface of the concrete detected in the non-horizontal direction;

thirdly, the thickness of the sprayed layer can be detected by methods such as punching or laser profiler, light band photography and the like, each position is counted respectively, the thickness of the sprayed layer at all the positions of the inspection holes should be more than 60% and not less than the designed thickness, the average thickness should not be less than the designed thickness, the minimum thickness should not be less than 1/2 of the designed thickness, in the weak and broken surrounding rock section, the thickness of the sprayed layer should not be less than the minimum thickness specified by the design, and the thickness of the concrete sprayed by the reinforcing mesh should not be less than 6cm

In the present invention, preferably, in the second step, the sand ratio, the cement mixing amount, the water-cement ratio, the additive type and the additive mixing amount in the test are respectively set to three levels, and a five-factor three-level method of an orthogonal test is adopted, so that 18 sets of tests are required, as shown in the following table:

in the present invention, preferably, in step two, the selection of the orthogonal test points is shown in the following table:

in the invention, preferably, the test in the step two mainly researches the concrete slump and the concrete compressive strength under different components and proportions, optimizes and adjusts the proportion of the components of the sprayed concrete and the content of the added fiber, and provides a rebound mechanism of the added fiber sprayed concrete and an optimal material proportion of the added fiber sprayed concrete in an indoor test.

In the invention, preferably, in the third step, the test is carried out according to the test method of mechanical properties of common concrete, the slump of each group is firstly measured, then 100 x 100mm samples are prepared, and the compressive strength of the concrete test blocks in the age of 7d, 14d and 28d is measured.

In the invention, preferably, in the fourth step, three concrete test blocks are manufactured in each group according to the standard requirements, and the average value of the three concrete test blocks is obtained by measuring the compressive strength of the three test blocks.

In the present invention, preferably, in the fifth step, the influence degree of each factor on the concrete slump obtained by the table is as follows: the water cement ratio, the admixture doping amount, the admixture type, the sand rate and the cement doping amount are larger than each other, for the concrete compressive strength of 7 days, the influence degree of each factor is as follows, the admixture type, the admixture doping amount, the cement doping amount, the sand rate and the water cement ratio is larger than each other, the influence of the water cement ratio on the slump constant is largest, the influence on the compressive strength of the concrete is smallest, and the influence of the added fibers on the compressive strength of the concrete is largest.

In the invention, preferably, in the step five, the slump of the concrete is obtained through a table and is in inverse proportion to the water-cement ratio, the larger the water-cement ratio is, the smaller the slump is, and the total slump is within the range of 106-114 mm, thereby meeting the requirements of sprayed concrete. The concrete with the age of 7 days has different compression strength due to different test results of mixture ratio and added components. The 15 th group test has the highest strength which reaches 30.13MPa, and the 15 th group test mixture ratio is cement: river sand: crushing stone: water: water reducing agent: accelerator: adding fiber 1: 1.98: 1.98: 0.41: 0.01: 0.07: 0.0065, group 1, the test results are minimal, 24.76 MPa. The average value of the compressive strength of the concrete in the 7-day age is 27.28MPa, the maximum value of the compressive strength of the concrete when polypropylene fibers are added is 27.37MPa and is 0.09MPa higher than the average value, the maximum value of the compressive strength of the concrete when chopped basalt fibers are added is 30.13MPa and is 2.85MPa higher than the average value, the maximum value of the compressive strength of the concrete when ultrahigh-performance synthetic fibers are added is 28.47MPa and is 1.19MPa higher than the average value, so the effect of the added fibers is seen from the result of the compressive strength of the concrete: chopped basalt fiber > ultra-high performance synthetic fiber > polypropylene fiber.

In the invention, preferably, in the step twelve, the calculation method of the concrete rebound rate is to calculate the rebound rate by weighing the total amount of the rebound falling concrete on site, and the calculation formula of the rebound rate is as follows: and J is the total resilience amount/the total concrete amount, wherein the total resilience amount is weighed during site construction, and the total concrete amount is obtained by weighing and calculating before construction.

EXAMPLE III

Referring to fig. 1-2, the present invention provides a technical solution: controlling the rebound formula of the sprayed concrete, wherein the material ratio of the sprayed concrete is as follows: sand and stone ratio: 45 to 55 percent

The cement mixing amount is as follows: 424kg/m3-464kg/m3

Water-cement ratio: 0.39-0.43

The types of the additives are as follows: polypropylene fiber, chopped basalt fiber and ultrahigh-performance synthetic fiber

The admixture mixing amount is as follows: 0.08 to 0.12 percent.

The formula for controlling the rebound of the sprayed concrete comprises the following steps:

the method comprises the following steps: firstly, controlling various data such as sand-stone ratio, cement mixing amount, admixture mixing amount, water-cement ratio and the like by adopting an indoor test mode, and recording the rebound rate of the sprayed concrete caused by the change of the ratio of each influencing factor;

step two: analyzing the experimental data, and determining the reasonable range of each influence factor so as to control the rebound quantity of the sprayed concrete within the optimal range;

step three: the experimental groupings are shown in the following table:

step four: the slump and the compressive strength of the concrete at the age of 7 days under various components are measured by the test and are shown in the following table:

step five: the influence degree of each factor on the slump and the concrete compressive strength is analyzed, the extreme difference analysis is respectively carried out on the influence degree, and the results are shown in the following table:

step six: preparing materials required by a field test, wherein cement, river sand, gravel, water, a water reducing agent, an accelerating agent and the like are all field materials, the materials need to meet the specification requirement, and chopped basalt fibers need to be purchased, and the specific purchase conditions are shown in the following table:

step seven: preparing a test device on site: the device comprises a large plastic cloth for collecting rebound concrete, an electronic scale for measuring the rebound concrete, a rebound tester for measuring the concrete strength, a die of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm, a cutting machine, a press machine, a wet spraying machine, a workbench frame, a mixing station and a concrete tank truck;

step eight: the method comprises the steps of performing a shotcrete resilience control test on site, wherein a section with a length of 3m is drawn, concrete tests with different proportions are respectively adopted, resilience amounts of concrete at different positions such as an arch crown and an arch waist are recorded, and 1.88 kg-2.82 kg of fiber is added into each concrete;

step nine: determining the section of sprayed concrete, and adding fibers into a mixing station according to the proportion, wherein the addition amount of the fibers in each concrete is 2.82 kg;

step ten: laying plastic cloth on the ground, spraying the positions respectively, and collecting the rebounded concrete;

step eleven: weighing the collected rebound quantity, and testing the concrete strength at different positions;

step twelve: the data of the section without adding fiber is tested according to the steps, and the following tests are required to be carried out for researching the effect of the added fiber in the concrete during construction: firstly, spraying concrete into a model of 45cm multiplied by 35cm multiplied by 12cm or 45cm multiplied by 20cm multiplied by 12cm during construction, processing the concrete into a cubic test block of 10cm multiplied by 10cm after the concrete reaches a certain strength, and curing for 28 days under standard conditions to perform a compressive strength test;

secondly, measuring the strength of the surface of the sprayed concrete by using a concrete strength resiliometer, dividing a measuring area according to the positions for measurement, wherein the measuring area is selected to be the side surface of the concrete detected by the resiliometer in the horizontal direction as far as possible, and when the requirement cannot be met, the resiliometer can be positioned on the pouring side surface, the surface or the bottom surface of the concrete detected in the non-horizontal direction;

thirdly, the thickness of the sprayed layer can be detected by methods such as punching or laser profiler, light band photography and the like, each position is counted respectively, the thickness of the sprayed layer at all the positions of the inspection holes should be more than 60% and not less than the designed thickness, the average thickness should not be less than the designed thickness, the minimum thickness should not be less than 1/2 of the designed thickness, in the weak and broken surrounding rock section, the thickness of the sprayed layer should not be less than the minimum thickness specified by the design, and the thickness of the concrete sprayed by the reinforcing mesh should not be less than 6cm

In the present invention, preferably, in the second step, the sand ratio, the cement mixing amount, the water-cement ratio, the additive type and the additive mixing amount in the test are respectively set to three levels, and a five-factor three-level method of an orthogonal test is adopted, so that 18 sets of tests are required, as shown in the following table:

in the present invention, preferably, in step two, the selection of the orthogonal test points is shown in the following table:

in the invention, preferably, the test in the step two mainly researches the concrete slump and the concrete compressive strength under different components and proportions, optimizes and adjusts the proportion of the components of the sprayed concrete and the content of the added fiber, and provides a rebound mechanism of the added fiber sprayed concrete and an optimal material proportion of the added fiber sprayed concrete in an indoor test.

In the invention, preferably, in the third step, the test is carried out according to the test method of mechanical properties of common concrete, the slump of each group is firstly measured, then 100 x 100mm samples are prepared, and the compressive strength of the concrete test blocks in the age of 7d, 14d and 28d is measured.

In the invention, preferably, in the fourth step, three concrete test blocks are manufactured in each group according to the standard requirements, and the average value of the three concrete test blocks is obtained by measuring the compressive strength of the three test blocks.

In the present invention, preferably, in the fifth step, the influence degree of each factor on the concrete slump obtained by the table is as follows: the water cement ratio, the admixture doping amount, the admixture type, the sand rate and the cement doping amount are larger than each other, for the concrete compressive strength of 7 days, the influence degree of each factor is as follows, the admixture type, the admixture doping amount, the cement doping amount, the sand rate and the water cement ratio is larger than each other, the influence of the water cement ratio on the slump constant is largest, the influence on the compressive strength of the concrete is smallest, and the influence of the added fibers on the compressive strength of the concrete is largest.

In the invention, preferably, in the step five, the slump of the concrete is obtained through a table and is in inverse proportion to the water-cement ratio, the larger the water-cement ratio is, the smaller the slump is, and the total slump is within the range of 106-114 mm, thereby meeting the requirements of sprayed concrete. The concrete with the age of 7 days has different compression strength due to different test results of mixture ratio and added components. The 15 th group test has the highest strength which reaches 30.13MPa, and the 15 th group test mixture ratio is cement: river sand: crushing stone: water: water reducing agent: accelerator: adding fiber 1: 1.98: 1.98: 0.41: 0.01: 0.07: 0.0065, group 1, the test results are minimal, 24.76 MPa. The average value of the compressive strength of the concrete in the 7-day age is 27.28MPa, the maximum value of the compressive strength of the concrete when polypropylene fibers are added is 27.37MPa and is 0.09MPa higher than the average value, the maximum value of the compressive strength of the concrete when chopped basalt fibers are added is 30.13MPa and is 2.85MPa higher than the average value, the maximum value of the compressive strength of the concrete when ultrahigh-performance synthetic fibers are added is 28.47MPa and is 1.19MPa higher than the average value, so the effect of the added fibers is seen from the result of the compressive strength of the concrete: chopped basalt fiber > ultra-high performance synthetic fiber > polypropylene fiber.

In the invention, preferably, in the step twelve, the calculation method of the concrete rebound rate is to calculate the rebound rate by weighing the total amount of the rebound falling concrete on site, and the calculation formula of the rebound rate is as follows: and J is the total resilience amount/the total concrete amount, wherein the total resilience amount is weighed during site construction, and the total concrete amount is obtained by weighing and calculating before construction.

In summary, when the fiber addition amount of each concrete is 2.82kg, the rebound rates of the arch crown, the arch shoulder and the arch waist in the tunnel are the lowest, the rebound rate of the arch crown is 10.3075% at the lowest, and the rebound rate of the arch shoulder is 10.3075% at the lowest.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.