阅读说明：本技术 一种全粘结支护锚杆施工方法 (Construction method of full-bonding support anchor rod ) 是由 李青伟 游杰勇 罗辉文 周同和 李晓明 杨迪 谢奉君 牛增聪 于 2020-06-12 设计创作，主要内容包括：本发明涉及建筑施工技术领域,且公开了一种全粘结支护锚杆施工方法,所述全粘结支护锚杆施工包括以下操作步骤：一、场地平整；二、锚杆制作；三．锚杆位置定位；四、钻机设备；五、挖泥浆池；六、钻机就位；七、钻机钻进；八、锚杆安装；九、孔口补浆及二次注浆；十、张拉。该全粘结支护锚杆施工方法,在粉质黏土等不良地质下的支护锚杆施工,本方法能有效避免锚杆成孔过程中塌孔、缩颈现象的发生,保证锚孔的直径满足设计要求；利用泥浆置换、二次注浆工艺,完全保证锚杆成孔内水泥浆的饱满度,使得支护锚杆全长与水泥砂浆充分粘结,保证锚杆体与土体充分接触,增强锚杆体与土体的粘结摩擦阻力,从而保证基坑支护的强度。(The invention relates to the technical field of building construction, and discloses a construction method of a full-bonding support anchor rod, which comprises the following operation steps: firstly, leveling a field; secondly, manufacturing an anchor rod; positioning the anchor rod; fourthly, drilling equipment; fifthly, digging a slurry pool; sixthly, positioning a drilling machine; seventhly, drilling by a drilling machine; eighthly, mounting an anchor rod; ninth, orifice grout replenishing and secondary grouting; tenthly, tensioning. According to the construction method of the full-bonding support anchor rod, the support anchor rod is constructed under unfavorable geology such as powdery clay, the phenomena of hole collapse and necking in the hole forming process of the anchor rod can be effectively avoided, and the diameter of the anchor hole is ensured to meet the design requirement; by utilizing the processes of slurry replacement and secondary grouting, the plumpness of cement slurry in the hole forming of the anchor rod is completely ensured, the full length of the support anchor rod is fully bonded with the cement mortar, the anchor rod body is fully contacted with the soil body, the bonding friction resistance of the anchor rod body and the soil body is enhanced, and the strength of foundation pit support is ensured.)

1. A construction method of a full-bonding support anchor rod is characterized by comprising the following steps: the construction of the full-bonding support anchor rod comprises the following operation steps:

firstly, the field is leveled

Before construction, the site of a construction area needs to be cleaned, and the site is leveled and compacted, so that the requirements of safe displacement and drilling of a drilling machine are met; meanwhile, the elevation of the leveled field is controlled, so that construction operation of drilling equipment is facilitated;

second, anchor rod manufacturing

(1) Witness sampling is carried out before the prestressed anchor cable for manufacturing the anchor rod is used, and the prestressed anchor cable can be used after the qualified anchor cable is inspected;

(2) when the anchor rod is manufactured, the anchor rod is manufactured in a factory shed as much as possible; the blanking length of the steel strand must meet the requirement of the design length and tensioning of the anchor rod bundle structure, and the steel strand is generally blanked according to the hole depth of +0.8 m;

(3) cutting the blanked steel strand by adopting a mechanical mode, strictly forbidding an arc cutting method, cutting the steel strand into steel strands with required length, placing a free section of the steel strand on an operation table for dirt and rust removal treatment, measuring the length of the free section after treatment, and sleeving a polyethylene pipe; meanwhile, winding and sealing the boundary of the free section and the anchoring section by using an adhesive tape;

(4) when the distance between the anchor rod bodies is 1.5m, a positioning bracket is arranged between the anchor rod bodies to ensure that the periphery of the anchor rod has enough slurry protection;

(5) the whole bundle of steel strands must be straight and must not cross, in order to ensure that the steel strands have certain rigidity, the binding space must not be greater than 0.5m, the binding mode adopts the tightening of binding wires, the head of the binding position is inverted to the tail position;

positioning anchor rod

Firstly, accurately measuring and placing the position of an anchor hole between piles according to the requirement of design arrangement, marking the hole opening position of an anchor rope at a site construction part by using red paint, wherein the error size of the horizontal direction of the anchor rod and the hole distance is not more than 50mm, the error size of the vertical direction of the anchor rod and the hole distance is not more than 100mm, the inclination size of the bottom of a drilled hole is not more than 3% of the anchoring diameter, the length of a rod body is not less than the designed length value, and the length value of a sleeve of a free section of a fully-bonded anchor rod is 0.5 m;

drilling rig equipment

After the drilling machine equipment enters a field, firstly, the qualification certificates of the drilling machine, the excavator and other equipment need to be checked, the drilling machine needs to be arranged for installation, debugging or detection, and the qualified drilling machine equipment which is not checked is not accurate to be put into use;

slurry digging pool

Excavating a mud pit by using an excavator on a construction site, wherein the mud pit is arranged to avoid a transportation road, 15-20 anchor rods share one mud pit, the organization and production are convenient, the site excavation is carried out, the area of the mud pit is about 3m multiplied by 5m, the depth value is about 2m, safety protection railings are arranged on the periphery of the mud pit, and warning signs are hung;

sixthly, positioning the drilling machine

The drilling machine equipment is moved to the anchor rod construction position, and the accuracy, the level and the stability of the rack are kept; checking the diameter value of the verification drilling tool to ensure that the diameter of the drilled hole is not less than the designed diameter value of the anchoring body of the anchor rod;

after the drilling machine is in place, the pre-inspection is needed, the deviation value between the center of the drill bit and the anchor rod position is less than 20mm, the angle of the drill rod is adjusted simultaneously, the inclination of the drill rod meets the design requirement, and the stable drilling operation can be performed only after the drill rod is qualified;

seventhly, drilling by a drilling machine

(1) When the drilling machine begins to drill, the depth of the drilling machine is controlled to be slightly pressed and slowly rotated by the depth of 3m, and the drilling speed is slow; in the drilling process, cement slurry is continuously injected into the hole opening through the drill rod, so that the hole wall is prevented from collapsing;

(2) in the drilling process, when the drilling depth is 3-5m, the inclination of the drill rod needs to be checked once, and when the inclination is found to exceed the standard, the adjustment is needed in real time; if the drill is stuck, the drill shakes and deviates, the drill is stopped, the reason is found out immediately, and the drilling can be continued after correct corrective measures are taken;

(3) in the drilling process, cement slurry needs to be continuously injected from a drill rod, and the drill slag is carried out of an orifice while the orifice is protected; in the construction process, a specially-assigned person often measures technical parameters of the cement slurry and mixes the consistency of the cement slurry in time;

(4) in the drilling process, the depth of a final hole is determined by measuring a drill rod, and the depth value of the final hole is not less than a design value; after the drilling depth meets the requirement, the drilling machine controls the drill rod to stop rotating and slowly pull out the drill rod, so that the hole wall cement slurry is solidified under the action of static pressure;

eight, anchor rod installation

After the length and the straightness of the anchor rod are detected, positioning a support and binding and checking a grouting pipe to be qualified, carrying out anchor rod hole entering under the side station of a supervision engineer, ensuring that the number of the anchor cable corresponds to the number of the holes when the anchor rod enters the holes, strictly advancing the anchor rod according to the inclination angle of the anchor hole, and smoothly advancing the anchor cable, strictly prohibiting the anchor cable from shaking, twisting and moving so as to prevent the anchor cable from being distorted and blocked and the like;

nine-hole orifice grout-filling and secondary grouting

Before the cement paste is initially set, the surface of the cement paste at the orifice is lowered, orifice grouting is carried out, secondary grouting is carried out immediately after the cement paste is initially set, and the cement paste is injected into the hole by using a grouting pipe;

ten, stretch-draw

When the strength of the anchoring body reaches over 75 percent of the design strength, performing tension locking, wherein the locking value meets the design requirement; and (4) when the stress loss exceeds 10% after locking for 48 hours, secondary supplementary tensioning is carried out, and the whole anchor rod construction process is completed after tensioning is completed.

2. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: in the anchor rod position location, the anchor hole positions which are measured, released and checked to be qualified need to be numbered, the numbers are used as the basis of anchor rod manufacturing numbers, construction can be carried out after the supervision engineer confirms that no errors exist, and retesting is carried out in the construction process.

3. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: in the drilling process of the down-the-hole drilling machine, cement slurry with the water-cement ratio of 1.2-1.6 is injected into a hole through a drill rod by using a slurry pump, the grouting pressure is 1.0-1.5MPa to form a slurry protection wall, the slurry overflow is kept at an orifice, the occurrence of hole collapse and necking in silty clay geology can be effectively prevented under the action of the cement slurry, and the subsequent steel strand anchor rod can be smoothly inserted.

4. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: in the drilling process, the geological condition of the stratum is definitely recorded according to the drilling and slurry returning slag-carrying conditions, and measures are taken in time if special stratum is met, so that the vibration and displacement of the drilling machine are avoided as much as possible in the whole drilling process.

5. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: and when the anchor is pulled out, cement slurry with the water-cement ratio of 0.5-0.6 is injected into the hole, mixed slurry of the slurry and the dilute cement slurry is replaced, the grouting pressure is 2.0-2.5MPa, the pressure balance in the hole is kept, and the diameter value and the strength value of the anchor are ensured to meet the design requirements.

6. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: in order to prevent slurry from solidifying and affecting the installation effect of the anchor rod, the installation of the anchor rod is completed within 20min after the drill rod is pulled out.

7. The construction method of the full-bonding support anchor rod according to claim 1, characterized in that: during secondary grouting, the grouting pressure is not less than 2MPa, the strength of the grouting body is not less than 30MPa, the anchor rod hole can be fully filled with cement slurry, and sufficient bonding or frictional resistance between the anchor rod body and a soil body is guaranteed.

Technical Field

The invention relates to the technical field of building construction, in particular to a construction method of a full-bonding support anchor rod.

Background

Along with the development of social economy, building construction engineering is higher and higher, the depth of a foundation pit is deeper and deeper, and in addition, the foundation pit is influenced by geological conditions, and the safety of the foundation pit becomes the largest hidden danger of building construction safety. At present, 80% of building construction engineering is high-rise buildings, foundation pit engineering becomes an important component of the high-rise buildings, and a pile-anchor supporting system is widely applied to the foundation pit engineering in the building construction engineering due to good supporting effect, small influence on earth excavation, main body construction and the like. Under the complex geological condition, especially under the unfavorable geological condition that water content is great such as silty clay, how to guarantee construction quality, improve the efficiency of construction, become a big difficult problem of foundation ditch engineering strut stock construction.

The conventional construction method for supporting the anchor rod at present comprises a dry hole forming technology of a down-the-hole drill, a sleeve follow-up technology of a spiral drill, a high-pressure rotary spraying technology of the down-the-hole drill and the like. The dry hole forming technology of the down-the-hole drill has high hole forming speed in dry operation, and the crawler type walking mode is convenient to move on a construction site, but cannot be used for wet operation with water. The spiral drilling machine sleeve following technology is high in usability and can be used in different environments, but the operation speed is low, the efficiency is low, and the labor consumption is large. The high-pressure rotary spraying technology of the down-the-hole drill has high construction speed, has high requirement on soil quality, viscous soil is not easy to be sprayed, a sandy soil rotary spraying body is easy to be overlarge, and the quality is not easy to guarantee.

Under the condition that geological conditions such as silty clay are poor, the shear strength of the silty clay is low, the deformation is large, the quality of the conventional construction technology cannot be guaranteed, and the speed is low. According to the project, by comparing various construction technologies, under the condition that the geology is poor such as silty clay and the like, the key technology innovation research and the field test of inserting the steel strand anchor rod behind the mud retaining wall of the down-the-hole drill are carried out, so that the construction efficiency is improved, and the construction quality is ensured.

Disclosure of Invention

The invention provides a construction method of a full-bonding support anchor rod, which aims to improve the construction quality of the support anchor rod under the unfavorable geological conditions of large water content such as powdery clay and the like, aims to ensure the anchoring diameter of the anchor rod, ensures that a drilled hole does not have hole collapse and necking, and simultaneously ensures the construction efficiency.

The invention provides the following technical scheme: the construction method of the full-bonding support anchor rod comprises the following operation steps:

firstly, the field is leveled

Before construction, the site of a construction area needs to be cleaned, and the site is leveled and compacted, so that the requirements of safe displacement and drilling of a drilling machine are met; meanwhile, the elevation of the leveled field is controlled, so that construction operation of drilling equipment is facilitated;

second, anchor rod manufacturing

(1) Witness sampling is carried out before the prestressed anchor cable for manufacturing the anchor rod is used, and the prestressed anchor cable can be used after the qualified anchor cable is inspected;

(2) when the anchor rod is manufactured, the anchor rod is manufactured in a factory shed as much as possible; the blanking length of the steel strand must meet the requirement of the design length and tensioning of the anchor rod bundle structure, and the steel strand is generally blanked according to the hole depth of +0.8 m;

(3) cutting the blanked steel strand by adopting a mechanical mode, strictly forbidding an arc cutting method, cutting the steel strand into steel strands with required length, placing a free section of the steel strand on an operation table for dirt and rust removal treatment, measuring the length of the free section after treatment, and sleeving a polyethylene pipe; meanwhile, winding and sealing the boundary of the free section and the anchoring section by using an adhesive tape;

(4) when the distance between the anchor rod bodies is 1.5m, a positioning bracket is arranged between the anchor rod bodies to ensure that the periphery of the anchor rod has enough slurry protection;

(5) the whole bundle of steel strands must be straight and must not cross, in order to ensure that the steel strands have certain rigidity, the binding space must not be greater than 0.5m, the binding mode adopts the tightening of binding wires, the head of the binding position is inverted to the tail position;

positioning anchor rod

Firstly, accurately measuring and placing the position of an anchor hole between piles according to the requirement of design arrangement, marking the hole opening position of an anchor rope at a site construction part by using red paint, wherein the error size of the horizontal direction of the anchor rod and the hole distance is not more than 50mm, the error size of the vertical direction of the anchor rod and the hole distance is not more than 100mm, the inclination size of the bottom of a drilled hole is not more than 3% of the anchoring diameter, the length of a rod body is not less than the designed length value, and the length value of a sleeve of a free section of a fully-bonded anchor rod is 0.5 m;

drilling rig equipment

After the drilling machine equipment enters a field, firstly, the qualification certificates of the drilling machine, the excavator and other equipment need to be checked, the drilling machine needs to be arranged for installation, debugging or detection, and the qualified drilling machine equipment which is not checked is not accurate to be put into use;

slurry digging pool

Excavating a mud pit by using an excavator on a construction site, wherein the mud pit is arranged to avoid a transportation road, 15-20 anchor rods share one mud pit, the organization and production are convenient, the site excavation is carried out, the area of the mud pit is about 3m multiplied by 5m, the depth value is about 2m, safety protection railings are arranged on the periphery of the mud pit, and warning signs are hung;

sixthly, positioning the drilling machine

The drilling machine equipment is moved to the anchor rod construction position, and the accuracy, the level and the stability of the rack are kept; checking the diameter value of the verification drilling tool to ensure that the diameter of the drilled hole is not less than the designed diameter value of the anchoring body of the anchor rod;

after the drilling machine is in place, the pre-inspection is needed, the deviation value between the center of the drill bit and the anchor rod position is less than 20mm, the angle of the drill rod is adjusted simultaneously, the inclination of the drill rod meets the design requirement, and the stable drilling operation can be performed only after the drill rod is qualified;

seventhly, drilling by a drilling machine

(1) When the drilling machine begins to drill, the depth of the drilling machine is controlled to be slightly pressed and slowly rotated by the depth of 3m, and the drilling speed is slow; in the drilling process, cement slurry is continuously injected into the hole opening through the drill rod, so that the hole wall is prevented from collapsing;

(2) in the drilling process, when the drilling depth is 3-5m, the inclination of the drill rod needs to be checked once, and when the inclination is found to exceed the standard, the adjustment is needed in real time; if the drill is stuck, the drill shakes and deviates, the drill is stopped, the reason is found out immediately, and the drilling can be continued after correct corrective measures are taken;

(3) in the drilling process, cement slurry needs to be continuously injected from a drill rod, and the drill slag is carried out of an orifice while the orifice is protected; in the construction process, a specially-assigned person often measures technical parameters of the cement slurry and mixes the consistency of the cement slurry in time;

(4) in the drilling process, the depth of a final hole is determined by measuring a drill rod, and the depth value of the final hole is not less than a design value; after the drilling depth meets the requirement, the drilling machine controls the drill rod to stop rotating and slowly pull out the drill rod, so that the hole wall cement slurry is solidified under the action of static pressure;

eight, anchor rod installation

After the length and the straightness of the anchor rod are detected, positioning a support and binding and checking a grouting pipe to be qualified, carrying out anchor rod hole entering under the side station of a supervision engineer, ensuring that the number of the anchor cable corresponds to the number of the holes when the anchor rod enters the holes, strictly advancing the anchor rod according to the inclination angle of the anchor hole, and smoothly advancing the anchor cable, strictly prohibiting the anchor cable from shaking, twisting and moving so as to prevent the anchor cable from being distorted and blocked and the like;

nine-hole orifice grout-filling and secondary grouting

Before the cement paste is initially set, the surface of the cement paste at the orifice is lowered, orifice grouting is carried out, secondary grouting is carried out immediately after the cement paste is initially set, and the cement paste is injected into the hole by using a grouting pipe;

ten, stretch-draw

When the strength of the anchoring body reaches over 75 percent of the design strength, performing tension locking, wherein the locking value meets the design requirement; and (4) when the stress loss exceeds 10% after locking for 48 hours, secondary supplementary tensioning is carried out, and the whole anchor rod construction process is completed after tensioning is completed.

Preferably, in the positioning of the anchor rod position, the anchor hole position which is measured, released and checked to be qualified needs to be numbered, the number is used as the basis of the anchor rod manufacturing number, construction can be carried out after the supervision engineer confirms that no error exists, and retesting is carried out in the construction process.

Preferably, in the drilling process of the down-the-hole drilling machine, a slurry pump is used for injecting cement slurry with a water-cement ratio of 1.2-1.6 into the hole through a drill rod, the grouting pressure is 1.0-1.5MPa to form a slurry protection wall, the slurry overflow is kept at the hole opening, the hole collapse and necking in silty clay geology can be effectively prevented under the action of the cement slurry, and the subsequent steel strand anchor rod can be smoothly inserted.

Preferably, the geological condition of the stratum is definitely recorded according to the drilling and slurry return slag-carrying conditions in the drilling process, measures are taken in time if special stratum is met, and the vibration and displacement of the drilling machine are avoided as far as possible in the whole drilling process.

Preferably, when the anchor is pulled out, cement slurry with a water-cement ratio of 0.5-0.6 is injected into the hole, mixed slurry of the slurry and dilute cement slurry is replaced, the grouting pressure is 2.0-2.5MPa, the pressure balance in the hole is kept, and the diameter value and the strength value of the anchor are ensured to meet the design requirements.

Preferably, in order to prevent slurry from solidifying and affecting the installation effect of the anchor rod, the installation of the anchor rod is completed within 20min after the drill rod is pulled out.

Preferably, during the secondary grouting, the grouting pressure is not less than 2MPa, the strength of the grouting body is not less than 30MPa, the anchor rod hole can be fully filled with cement paste, and sufficient bonding or frictional resistance between the anchor rod body and a soil body is ensured.

The invention has the following beneficial effects:

1. according to the construction method of the full-bonding support anchor rod, the support anchor rod is constructed under unfavorable geology such as powdery clay, the phenomena of hole collapse and necking in the hole forming process of the anchor rod can be effectively avoided, and the diameter of the anchor hole is ensured to meet the design requirement.

2. According to the construction method of the full-bonding support anchor rod, the cement slurry wall protection, static pressure consolidation and slurry replacement are adopted to reinforce the side wall of the formed hole in the construction process, so that the strength of the hole wall can meet the requirement of the support anchor rod construction.

3. According to the construction method of the full-bonding support anchor rod, the plumpness of cement slurry in the anchor rod hole is completely ensured by utilizing slurry replacement and secondary grouting processes, so that the full length of the support anchor rod is fully bonded with cement mortar, the anchor rod body is ensured to be fully contacted with a soil body, the bonding friction resistance of the anchor rod body and the soil body is enhanced, and the strength of foundation pit support is ensured.

4. The construction method of the fully-bonded support anchor rod can greatly reduce the phenomenon of time limit delay caused by unqualified construction quality of the support anchor rod in a short time for the project with short construction period, and effectively ensures the continuity of the field construction process.

Drawings

FIG. 1 is a flow chart of the construction process of the present invention;

fig. 2 is a drawing of the construction equipment of the full-bonding support anchor rod of the 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.

Referring to fig. 1-2, a method for constructing a fully-bonded support anchor includes the following steps:

firstly, the field is leveled

Before construction, the site of a construction area needs to be cleaned, and the site is leveled and compacted, so that the requirements of safe displacement and drilling of a drilling machine are met; meanwhile, the elevation of the leveled field is controlled, so that construction operation of drilling equipment is facilitated;

second, anchor rod manufacturing

(1) Witness sampling is carried out before the prestressed anchor cable for manufacturing the anchor rod is used, and the prestressed anchor cable can be used after the qualified anchor cable is inspected;

(2) when the anchor rod is manufactured, the anchor rod is manufactured in a factory shed as much as possible; the blanking length of the steel strand must meet the requirement of the design length and tensioning of the anchor rod bundle structure, and the steel strand is generally blanked according to the hole depth of +0.8 m;

(3) cutting the blanked steel strand by adopting a mechanical mode, strictly forbidding an arc cutting method, cutting the steel strand into steel strands with required length, placing a free section of the steel strand on an operation table for dirt and rust removal treatment, measuring the length of the free section after treatment, and sleeving a polyethylene pipe; meanwhile, winding and sealing the boundary of the free section and the anchoring section by using an adhesive tape;

(4) when the distance between the anchor rod bodies is 1.5m, a positioning bracket is arranged between the anchor rod bodies to ensure that the periphery of the anchor rod has enough slurry protection;

(5) the whole bundle of steel strands must be straight and must not cross, in order to ensure that the steel strands have certain rigidity, the binding space must not be greater than 0.5m, the binding mode adopts the tightening of binding wires, the head of the binding position is inverted to the tail position;

positioning anchor rod

Firstly, accurately measuring and placing the position of an anchor hole between piles according to the requirement of design arrangement, marking the hole opening position of an anchor rope at a site construction part by using red paint, wherein the error size of the horizontal direction of the anchor rod and the hole distance is not more than 50mm, the error size of the vertical direction of the anchor rod and the hole distance is not more than 100mm, the inclination size of the bottom of a drilled hole is not more than 3% of the anchoring diameter, the length of a rod body is not less than the designed length value, and the length value of a sleeve of a free section of a fully-bonded anchor rod is 0.5 m; in the positioning of the anchor rod position, the anchor hole positions which are measured, released and checked to be qualified need to be numbered, the number is used as the basis of the anchor rod manufacturing number, construction can be carried out after the supervision engineer confirms that no error exists, and retesting is carried out in the construction process;

drilling rig equipment

After the drilling machine equipment enters a field, firstly, the qualification certificates of the drilling machine, the excavator and other equipment need to be checked, the drilling machine needs to be arranged for installation, debugging or detection, and the qualified drilling machine equipment which is not checked is not accurate to be put into use;

slurry digging pool

Excavating a mud pit by using an excavator on a construction site, wherein the mud pit is arranged to avoid a transportation road, 15-20 anchor rods share one mud pit, the organization and production are convenient, the site excavation is carried out, the area of the mud pit is about 3m multiplied by 5m, the depth value is about 2m, safety protection railings are arranged on the periphery of the mud pit, and warning signs are hung;

sixthly, positioning the drilling machine

The drilling machine equipment is moved to the anchor rod construction position, and the accuracy, the level and the stability of the rack are kept; checking the diameter value of the verification drilling tool to ensure that the diameter of the drilled hole is not less than the designed diameter value of the anchoring body of the anchor rod;

after the drilling machine is in place, the pre-inspection is needed, the deviation value between the center of the drill bit and the anchor rod position is less than 20mm, the angle of the drill rod is adjusted simultaneously, the inclination of the drill rod meets the design requirement, and the stable drilling operation can be performed only after the drill rod is qualified;

seventhly, drilling by a drilling machine

(1) When the drilling machine begins to drill, the depth of the drilling machine is controlled to be slightly pressed and slowly rotated by the depth of 3m, and the drilling speed is slow; in the drilling process, cement slurry is continuously injected into the hole opening through the drill rod, so that the hole wall is prevented from collapsing; in the drilling process of the down-the-hole drilling machine, cement slurry with the water-cement ratio of 1.2-1.6 is injected into a hole through a drill rod by using a slurry pump, the grouting pressure is 1.0-1.5MPa to form a slurry protection wall, the slurry overflow is kept at the hole opening, the hole collapse and necking in silty clay geology can be effectively prevented under the action of the cement slurry, and the subsequent steel strand anchor rod can be smoothly inserted;

(2) in the drilling process, when the drilling depth is 3-5m, the inclination of the drill rod needs to be checked once, and when the inclination is found to exceed the standard, the adjustment is needed in real time; if the drill is stuck, the drill shakes and deviates, the drill is stopped, the reason is found out immediately, and the drilling can be continued after correct corrective measures are taken;

(3) in the drilling process, cement slurry needs to be continuously injected from a drill rod, and the drill slag is carried out of an orifice while the orifice is protected; in the construction process, a specially-assigned person often measures technical parameters of the cement slurry and mixes the consistency of the cement slurry in time; in the drilling process, according to the drilling and slurry returning slag-carrying conditions, the geological conditions of the stratum are definitely recorded, and if special stratum is met, measures are taken in time, so that the vibration and displacement of the drilling machine are avoided as much as possible in the whole drilling process;

(4) in the drilling process, the depth of a final hole is determined by measuring a drill rod, and the depth value of the final hole is not less than a design value; after the drilling depth meets the requirement, the drilling machine controls the drill rod to stop rotating and slowly pull out the drill rod, so that the hole wall cement slurry is solidified under the action of static pressure; when the anchor is pulled out, cement slurry with the water-cement ratio of 0.5-0.6 is injected into the hole, mixed slurry of the slurry and the dilute cement slurry is replaced, the grouting pressure is 2.0-2.5MPa, the pressure balance in the hole is kept, and the diameter value and the strength value of the anchor are ensured to meet the design requirements;

eight, anchor rod installation

After the length and the straightness of the anchor rod are detected, positioning a support and binding and checking a grouting pipe to be qualified, carrying out anchor rod hole entering under the side station of a supervision engineer, ensuring that the number of the anchor cable corresponds to the number of the holes when the anchor rod enters the holes, strictly advancing the anchor rod according to the inclination angle of the anchor hole, and smoothly advancing the anchor cable, strictly prohibiting the anchor cable from shaking, twisting and moving so as to prevent the anchor cable from being distorted and blocked and the like; in order to prevent slurry from solidifying and affecting the installation effect of the anchor rod, the installation of the anchor rod is finished within 20min after the drill rod is pulled out;

nine-hole orifice grout-filling and secondary grouting

Before the cement paste is initially set, the surface of the cement paste at the orifice is lowered, orifice grouting is carried out, secondary grouting is carried out immediately after the cement paste is initially set, and the cement paste is injected into the hole by using a grouting pipe; during secondary grouting, the grouting pressure is not less than 2MPa, the strength of the grouting body is not less than 30MPa, the anchor rod hole can be fully filled with cement paste, and sufficient bonding or frictional resistance between the anchor rod body and a soil body is ensured;

ten, stretch-draw

When the strength of the anchoring body reaches over 75 percent of the design strength, performing tension locking, wherein the locking value meets the design requirement; and (4) when the stress loss exceeds 10% after locking for 48 hours, secondary supplementary tensioning is carried out, and the whole anchor rod construction process is completed after tensioning is completed.

The working principle and the construction technology utilize a down-the-hole drill to inject cement slurry with the cement-water ratio of 1.2-1.6 into a hole through a drill rod in the drilling process, and the slurry is kept overflowing from the hole opening to form a slurry protection wall, so that hole collapse and necking in silty clay geology can be effectively prevented. After the drilling depth meets the requirement, the drill rod stops rotating and is slowly pulled out, the hole wall is solidified by static pressure, mixed slurry of slurry and cement slurry is replaced by injecting cement slurry with a water-cement ratio of 0.5-0.6 into the hole while pulling out, the hole is filled, the pressure balance in the hole is ensured, the diameter and the strength of an anchoring body meet the design requirement, the manufactured steel strand rod body is inserted into the hole, the construction of the anchor rod is completed after secondary grouting, the construction effect of full-length bonding between the anchor rod support and the cement slurry is achieved, and the quality and the safety of foundation pit support construction are ensured.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

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.