阅读说明：本技术 一种在动水砂层中的旋喷桩成桩方法 (Rotary jet grouting pile forming method in dynamic water sand layer ) 是由 古伟斌 王冬英 蔡强 李世添 蔺青涛 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种在动水砂层中的旋喷桩成桩方法,包括S1、采用地质钻机进行钻孔；S2、采用粘土泥粉并掺入高效高发膨润土向钻孔内进行第一次旋喷喷射；S3、采用水泥浆和水玻璃同时向钻孔内进行第二次旋喷喷射；第二次旋喷喷射的压力比第一次旋喷的压力小,第二次旋喷喷射的提升速度比第一次旋喷的提升速度大。本发明釆用在动水砂层中二次旋喷喷射；在同一钻孔内采用二次旋喷喷射,第一次旋喷喷射的粘土粉和膨润土浆来先稳定砂层和填充砂层的砂粒之间的空隙,把砂层改变成砂土混合体；在第二次喷射的水泥浆中添加高效减水剂,可防止第二次旋喷喷射的水泥浆在还没有凝固前被地下水稀释或冲走、带走,提高了成桩的成功率,保证旋喷桩的质量。(The invention discloses a method for forming a rotary jet grouting pile in a flowing water sand layer, which comprises the following steps of S1, drilling by a geological drilling machine; s2, carrying out primary rotary spraying on the clay mud powder and the high-efficiency high-foaming bentonite mixed into the drilled hole; s3, simultaneously carrying out secondary rotary spraying on the cement slurry and the water glass in the drilled hole; the pressure of the second rotary spraying is smaller than that of the first rotary spraying, and the lifting speed of the second rotary spraying is larger than that of the first rotary spraying. The invention adopts secondary rotary spraying in a flowing water sand layer; adopting secondary rotary spraying in the same drill hole, stabilizing gaps between sand layers and sand grains filling the sand layers by clay powder and bentonite slurry sprayed in the primary rotary spraying, and changing the sand layers into sand-soil mixtures; the high-efficiency water reducing agent is added into the cement paste sprayed for the second time, so that the cement paste sprayed for the second time by rotary spraying can be prevented from being diluted or washed away and taken away by underground water before solidification, the success rate of pile forming is improved, and the quality of the rotary spraying pile is ensured.)

1. A rotary jet grouting pile forming method in a dynamic water sand layer is characterized by comprising the following steps:

s1, after the position of the drill hole is determined, drilling the drill hole at the corresponding position by using a geological drilling machine;

s2, adopting clay mud powder and doping high-efficiency high-foaming bentonite to perform primary rotary spraying in the drill hole to stabilize the gap between the sand layer and the sand filling the sand layer, and changing the sand layer into a sand-soil mixture;

s3, simultaneously carrying out secondary rotary spraying on the cement slurry and the water glass in the drilled hole; the pressure of the second rotary spraying is lower than that of the first rotary spraying, and the lifting speed of the second rotary spraying is higher than that of the first rotary spraying.

2. The pile forming method of the rotary jet grouting pile in the flowing water sand layer as claimed in claim 1, wherein the pressure of the first rotary jet grouting is 25-28MPa, and the lifting speed is 10 cm/min; the pressure of the second rotary spraying is 22-25MPa, and the lifting speed is 12 cm/min.

3. The method for forming the jet grouting pile in the flowing water sand layer according to claim 1, wherein the concrete content of the step S1 is as follows:

adopting a GPS instrument to perform hole site lofting according to a hole site layout diagram, wherein the deviation between the hole site of the open holes of all pile holes and the designed hole site is not more than 20 mm; and then, constructing pile hole positions according to three sequences, firstly performing drilling construction of the first sequence of holes in block section construction, and spacing the drilling between the upper sequence of holes and the lower sequence of holes for 48 hours.

4. The pile forming method of the rotary jet grouting pile in the flowing water sand layer as claimed in claim 1, wherein the first rotary jet grouting and the second rotary jet grouting are both constructed by three hole jumping operations in three steps, and the interval between the next step and the previous step is 48 hours.

5. The pile-forming method of the rotary jet grouting pile in the flowing water sand layer as claimed in any one of claims 1 to 4, wherein the rotary jet rotating speed of the first rotary jet and the second rotary jet is 12-15 r/min.

6. The pile forming method of the rotary jet grouting pile in the flowing water sand layer as claimed in claim 1, wherein the spraying amount of the first rotary jet grouting is 250-300 Kg/m, and the mixing proportion of the high-efficiency high-expansion bentonite is 5%.

7. The pile forming method of the jet grouting pile in the flowing water sand layer as claimed in claim 1, wherein a high efficiency water reducing agent is mixed in the cement paste.

8. The pile forming method of the rotary jet grouting pile in the dynamic water sand layer is characterized in that the water and cement ratio of the cement paste is as follows: 0.8-1: 1, adding a high-efficiency water reducing agent into cement paste, wherein the proportion of water, cement, the high-efficiency water reducing agent and water glass is as follows: 0.8-1: 1: 0.005: 0.005.

9. the method for forming the rotary jet grouting pile in the flowing water sand layer as claimed in claim 8, wherein the cement is P042.5R Portland cement.

10. The pile-forming method of the jet grouting pile in the flowing water sand layer is characterized in that the depth of the drill hole extending into the impervious layer is not less than 1 meter.

Technical Field

The invention relates to a rotary jet grouting pile forming method, in particular to a rotary jet grouting pile forming method in a dynamic water sand layer.

Background

In the building, traffic and water conservancy projects, a basement is required to be built or a trench is required to be excavated to build a foundation; then, foundation pit supporting and waterproof curtains are needed. A supporting pile of a deep foundation pit is usually cast-in-place pile, a waterproof curtain is usually formed by adopting a phi 600 stirring pile, a large-diameter stirring pile and a three-shaft stirring pile to stop water at the periphery of the cast-in-place pile, or 2 single-pipe or double-pipe jet grouting piles are additionally arranged between the supporting cast-in-place piles to stop water. After the application, the seepage-resisting and seepage-proofing properties of the cement-soil pile formed by stirring the stirring pile or the jet grouting pile are utilized to play a role in blocking and intercepting underground water.

When the waterproof curtain is used in areas with complex hydrogeology, such as near rivers, lakes, coastal areas and the like, and under the pressure action of underground water at the same time of a deep sand layer or a pebble layer rich in water or when the underground water rises and falls along with tides, cement slurry added into cement soil formed by the stirring piles or the jet grouting piles is not solidified and is flushed and taken away by the water, so that the stirring piles or the jet grouting piles cannot be formed, the waterproof curtain cannot achieve the functions of stopping water and intercepting the underground water, water leakage of a foundation pit is caused, and serious quality accidents of engineering are caused.

Disclosure of Invention

The invention aims to solve the problems and provides a rotary jet grouting pile forming method in a dynamic water sand layer, which has high pile forming success rate, stable quality and reliability. The method adopts secondary rotary spraying and jetting; the clay powder and the bentonite slurry are firstly sprayed in the first rotary spraying, the cement slurry is sprayed in the second rotary spraying, and the pressure of the first rotary spraying is higher than that of the second rotary spraying and the lifting speed is lower; wherein, the clay powder and bentonite slurry sprayed by the first rotary spraying firstly stabilize the gap between the sand layer and the sand grains filling the sand layer, and change the sand layer into a sand-soil mixture; the additive is added into the cement paste sprayed for the second time, so that the cement paste sprayed for the second time by rotary spraying can be prevented from being diluted or washed away and taken away by underground water before solidification, the success rate of pile forming is improved, and the quality of the rotary spraying pile is ensured.

The purpose of the invention can be achieved by adopting the following technical scheme:

a rotary jet grouting pile forming method in a dynamic water sand layer comprises the following steps:

s1, after the position of the drill hole is determined, drilling the drill hole at the corresponding position by using a geological drilling machine;

s2, adopting clay mud powder and doping high-efficiency high-foaming bentonite to perform primary rotary spraying in the drill hole to stabilize the gap between the sand layer and the sand filling the sand layer, and changing the sand layer into a sand-soil mixture;

s3, simultaneously carrying out secondary rotary spraying on the cement slurry and the water glass in the drilled hole; the pressure of the second rotary spraying is lower than that of the first rotary spraying, and the lifting speed of the second rotary spraying is higher than that of the first rotary spraying.

Further, the pressure of the first rotary spraying is 25-28MPa, and the lifting speed is 10 cm/min; the pressure of the second rotary spraying is 22-25MPa, and the lifting speed is 12 cm/min.

Further, the specific content of step S1 is:

adopting a GPS instrument to perform hole site lofting according to a hole site layout diagram, wherein the deviation between the hole site of the open holes of all pile holes and the designed hole site is not more than 20 mm; and then, constructing pile hole positions according to three sequences, firstly performing drilling construction of the first sequence of holes in block section construction, and spacing the drilling between the upper sequence of holes and the lower sequence of holes for 48 hours.

Further, the first rotary jet and the second rotary jet are constructed by three times of hole jumping according to three-sequence holes, and the interval between the next sequence and the previous sequence is 48 hours.

Further, the rotating speed of the first rotary spraying and the second rotary spraying is 12-15 r/min.

Furthermore, the spraying amount of the first rotary spraying is 250-300 Kg/m, and the doping proportion of the high-efficiency high-foaming bentonite is 5%.

Further, a high-efficiency water reducing agent is mixed in the cement slurry.

Further, the ratio of water to cement of the cement paste is as follows: 0.8-1: 1, adding a high-efficiency water reducing agent into cement paste, wherein the proportion of water, cement, the high-efficiency water reducing agent and water glass is as follows: 0.8-1: 1: 0.005: 0.005.

further, P042.5R portland cement is adopted as the cement.

Further, the depth of the drill hole extending into the impervious layer is not less than 1 meter.

Further, a drill bit is arranged at the front end of the drill rod.

The implementation of the invention has the following beneficial effects:

the invention adopts a method of secondary rotary spraying in a flowing water sand layer; by using secondary jet grouting in the same borehole: the clay powder and the bentonite slurry are firstly sprayed in the first rotary spraying, the cement slurry is sprayed in the second rotary spraying, and the pressure of the first rotary spraying is higher than that of the second rotary spraying and the lifting speed is lower; wherein, the clay powder and bentonite slurry sprayed by the first rotary spraying firstly stabilize the gap between the sand layer and the sand grains filling the sand layer, and change the sand layer into a sand-soil mixture; the high-efficiency water reducing agent is added into the cement paste sprayed for the second time, so that the cement paste sprayed for the second time by rotary spraying can be prevented from being diluted or washed away and taken away by underground water before solidification, the success rate of pile forming is improved, and the quality of the rotary spraying pile is ensured.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a construction flow diagram of a jet grouting pile forming method in a dynamic water sand layer.

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 (b):

referring to fig. 1, the embodiment relates to a method for forming a jet grouting pile in a flowing water sand layer, which comprises the following steps:

construction preparation and technical bottom crossing: before construction, the work of temporary construction, water and electricity, equipment, pipelines and the like required by construction should be finished. In the construction process, the following technical requirements need to be noticed: the excavated foundation pit is subjected to single-pipe rotary spraying, the rotary spraying pile without excavation can be subjected to double-pipe rotary spraying, the air pressure is 0.7MPa, slurry is blown everywhere in the excavated foundation pit and is emitted when compressed air is used, and adverse factors can influence the safety of the foundation pit, so that the excavated foundation pit is subjected to single-pipe rotary spraying; and each worker is ensured to master the relevant parameters and quality control key points of the rotary spraying pile in each time of secondary rotary spraying construction.

S1, after the position of the drill hole is determined, drilling the drill hole at the corresponding position by using a geological drilling machine; adopting a GPS instrument to perform hole site lofting according to a hole site layout diagram, wherein the deviation between the hole site of the open holes of all pile holes and the designed hole site is not more than 20 mm; and then, constructing pile hole positions according to three sequences, firstly performing drilling construction of the first sequence of holes in block section construction, and spacing the drilling between the upper sequence of holes and the lower sequence of holes for 48 hours. The drilling machine is positioned according to the specified hole position, and the angle of the drilling machine is checked before the hole is opened; after the hole positions are aligned, the drilling machine is firmly fixed and cannot be moved randomly; and (3) forming holes by using a geological drilling machine, wherein the hole diameter of each drilled hole is phi 90mm, the depth of each drilled hole extending into the impervious bed is not less than 1m, the depth of each drilled hole is at least 10cm deeper than the length of the designed pile, and the verticality deviation of the drilled holes is not more than 1%.

The jet grouting pile driver is put in place according to the pile hole position, the spray rod drill bit is aligned to the center of the hole position, meanwhile, the jet grouting drill is leveled, the placement is stable, the pile driver and the drill rod are calibrated by adopting a horizontal ruler, the pile driver is horizontal, the verticality deviation of the drill rod is not more than 1 percent, and the drill rod of the guide frame is vertical to the ground.

And (3) water is sprayed while drilling in the drilling process, the water pressure is not more than 0.8Mpa (generally 0.5-0.8 MPa), and after each section of drill rod is drilled to the depth, the drill rod is connected and then drilled until the drilling depth is reached.

S2, adopting clay mud powder and doping high-efficiency high-foaming bentonite to perform primary rotary spraying in the drill hole to stabilize the gap between the sand layer and the sand filling the sand layer, and changing the sand layer into a sand-soil mixture; first rotary spraying of slurry: the spraying amount of the first rotary spraying is 250-300 Kg/m, and the doping proportion of the high-efficiency high-foaming bentonite is 5%.

S3, simultaneously carrying out secondary rotary spraying on the cement slurry and the water glass in the drilled hole; the pressure of the second rotary spraying is lower than that of the first rotary spraying, and the lifting speed of the second rotary spraying is higher than that of the first rotary spraying. And the first rotary jet and the second rotary jet are constructed by three times of hole jumping according to three-sequence holes, and the interval between the next sequence and the previous sequence is 48 hours. Spraying cement slurry for the second time: the cement slurry is mixed with a high-efficiency water reducing agent. The cement is P042.5R Portland cement. The ratio of water to cement in the cement paste is: 0.8-1: 1, adding a high-efficiency water reducing agent into cement paste, wherein the proportion of water, cement, the high-efficiency water reducing agent and water glass is as follows: 0.8-1: 1: 0.005: 0.005.

high-pressure equipment and a pipeline system are checked before jet grouting, and the pressure and the discharge capacity of the equipment must meet the design requirements; sealing rings of all parts are good, sundries cannot be left in all channels and nozzles, a high-pressure water jetting test is carried out, and slurry can be jetted after the sealing rings are qualified; the number of the rotary spraying nozzles is 1, and the size of each nozzle is phi 2.6 mm; the rotary spraying adopts secondary rotary spraying to form a pile, the spraying pressure of the first rotary spraying is larger than that of the second rotary spraying, and the lifting speed of the first rotary spraying is slower than that of the second rotary spraying; and after the first rotary spraying injection operation is finished, the rotary spraying drill rod is immediately subjected to second rotary spraying injection after reaching the bottom by utilizing the self-drilling function of the rotary spraying machine. The pressure of the first rotary spraying is 25-28MPa, and the lifting speed is 10 cm/min; the pressure of the second rotary spraying is 22-25MPa, and the lifting speed is 12 cm/min. The rotating speed of the first rotary jet and the second rotary jet is 12-15 r/min.

S4, lifting the drill rod while carrying out rotary spraying according to preset parameters until grouting is carried out to the pile top, starting from 1.0m below the pile top when the rotary spraying pipe is lifted to be close to the pile top, and slowly lifting from 0.5m downwards when the rotary spraying pipe is lifted to the top slowly until the pile top is reached so as to ensure the pile top grout surface effect.

S5, after the construction of the rotary jet pile for the second time of the rotary jet, washing the grouting pipe and other equipment by using clear water to prevent solidification and blockage; and starting the high-pressure pump, cleaning cement slurry remained in all pipelines until the cement slurry is clean, cleaning the adhered soil on the drill bit of the cement spraying pipe, flushing the high-pressure nozzle with clean water through the high-pressure pump, and moving the machine to enter the next pile hole point.

S6, quality inspection: and after the construction is finished, performing quality inspection through drilling and core pulling and foundation pit excavation. The core pulling detection shows that the core sample is completely and continuously solidified in a sand layer, the core sample strength is more than or equal to 1MPa after 28 days, and the requirement is met when no obvious water leakage exists on the side wall of the foundation pit after excavation.

S7, pile testing: before formal construction, 3 secondary rotary jet grouting pile construction tests are firstly carried out, and the pile forming effect is tested. And 7 days later, performing drilling and core-pulling detection, mainly detecting the pile forming condition, the strength and the complete continuity of the consolidation body in the sand layer, and performing comprehensive construction after pile testing is successful.

A rotary-spraying pile-forming method in a moving water-sand layer adopts a secondary rotary-spraying method in the same hole, wherein clay powder and bentonite slurry are firstly sprayed in a first rotary-spraying mode, cement slurry is sprayed in a second rotary-spraying mode, the pressure of the first rotary-spraying mode is higher than that of the second rotary-spraying mode, the lifting speed is slower, gaps between sand grains of a sand layer and sand grains filling the sand layer are firstly stabilized by the clay powder and the bentonite slurry sprayed in the first rotary-spraying mode, the sand layer is changed into a sand-soil mixture, and then an additive is added into the cement slurry sprayed in the second rotary-spraying mode, so that the cement slurry sprayed in the second rotary-spraying mode is prevented from being diluted or washed away and taken away by underground water before solidification, a rotary-spraying pile is prevented from being formed, and the quality of the rotary-spraying pile is guaranteed and improved.

The invention adopts a method of secondary rotary spraying in a flowing water sand layer; by using secondary jet grouting in the same borehole: the clay powder and the bentonite slurry are firstly sprayed in the first rotary spraying, the cement slurry is sprayed in the second rotary spraying, and the pressure of the first rotary spraying is higher than that of the second rotary spraying and the lifting speed is lower; wherein, the clay powder and bentonite slurry sprayed by the first rotary spraying firstly stabilize the gap between the sand layer and the sand grains filling the sand layer, and change the sand layer into a sand-soil mixture; the additive (high efficiency water reducing agent) is added into the cement paste sprayed for the second time, so that the cement paste sprayed for the second time by rotary spraying can be prevented from being diluted or washed away and taken away by underground water before solidification, the success rate of pile forming is improved, and the quality of the rotary spraying pile is ensured.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.