Bridge foundation pile construction method
By combining rotary drilling rigs and mud wall protection technology with the use of anti-seepage layers, the problems of borehole wall collapse and uneven settlement in bridge pile foundation construction have been solved, achieving efficient and economical bridge pile foundation construction.
Patent Information
- Application Number
- CN202310840704.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-10
- Publication Date
- 2025-01-10
AI Technical Summary
Existing bridge pile foundation construction in underwater environments is prone to hole wall collapse and uneven settlement, affecting the quality of bridge structure, and is also complex and costly.
Rotary drilling rigs are used for drilling, mud wall protection technology is used to ensure the stability of the borehole wall, and an enlarged steel cage and anti-seepage layer are set during the drilling process. The foundation piles are formed by underwater concrete pouring, and mud and anti-seepage layer materials with specific ratios are used to improve the stability and waterproof performance of the borehole wall.
It improves the bearing capacity and seismic strength of the pile foundation, reduces construction difficulty and construction period, enhances economic benefits, and ensures the uniformity of settlement and overall stability of the pile foundation.
Smart Images
Figure CN119287893A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a bridge foundation pile construction method. Background Art
[0002] With the rapid development of economy, the demand for transportation has increased rapidly, and the construction of bridges has also developed rapidly. Many large, medium and small bridges need to be built. Bridges are often built across rivers with non-rapid water or shallow still lakes or on land. The bridge foundation is the lowest part of the bridge structure that directly contacts the foundation, and is an important part of the bridge substructure. The bridge foundation is directly located on the rock, soil foundation, below the surface water level or on the fault zone. After the foundation and foundation are subjected to various loads, they will produce stress and deformation. In order to ensure the safety and normal use of the bridge, the foundation and pile foundation must have sufficient strength, rigidity and overall stability to prevent excessive horizontal displacement or uneven settlement. Most ordinary pile foundations are located below the surface water level. The water content of the bridge pile foundation construction point is large, the construction process is relatively complicated, and the pile foundation support cost is high. Improper operation is easy to cause hole collapse and buried drilling. After the hole is cleaned, the inside of the hole is in a hollow state, and the side wall of the foundation pile hole is easy to collapse under water pressure, which is bound to cause uneven settlement of the adjacent pile foundation and affect the quality of the bridge structure. Summary of the invention
[0003] The purpose of the present invention is to provide a bridge foundation pile construction method, which can improve the stability of the hole wall, avoid the problem of surrounding soil extruding and damaging the hole wall, improve the bearing capacity and seismic strength of the foundation pile, and has low construction difficulty, short construction period and high economic benefits. In order to achieve the above purpose, the present invention adopts the following technical effects:
[0004] According to one aspect of the present invention, a bridge foundation pile construction method is provided, the foundation pile construction method comprising the following steps:
[0005] Step 1: According to the design drawings and on-site geological survey, the construction site is excavated and leveled. After the site is leveled, a two-level slope protection wall with a ratio of at least 1:1.5 is built around the foundation piles, and a water retaining weir is set outside and at the root of the slope protection wall;
[0006] Step 2: Plan the scope of the foundation piles within the scope of the construction site and mark the center of the piles, and set up a mud pool outside the foundation piles. Then use a rotary drilling rig to drill holes. When rotating and squeezing the drill bit, make sure that the drill bit is full of mud and then pull out the drill bit to replenish the mud. After the drilling is completed, remove the sediment at the bottom of the pile hole and keep drilling. Drill to the layer where the bottom expansion construction is expected to be carried out to form the foundation pile hole. According to the geological conditions, the slope of the drilling rig working site shall not be greater than 2%. The drill bit can be a pick or a simple cone drill bit, a conical bucket tooth spiral drill bit, a double-bottom pick rotary drilling bucket, or a double-headed double-screw conical spiral drill bit. The drill rod uses a machine-locked drill rod. According to the drilling situation of the rotary drilling rig, timely replenish the loss and leakage of slurry to ensure that the slurry is always 1.5 to 2.0 m higher than the water level outside the foundation pile hole and the groundwater level, so as to ensure the concentration of the slurry during the drilling process and effectively prevent accidents such as hole collapse and hole locking. The mud is used as the wall-protecting mud colloid of the pile hole to improve the stability of the hole wall.
[0007] Step 3, after drilling the foundation pile hole, measure the hole depth, hole diameter, hole position, and check the elevation and rock properties of the pile bottom, then expand the rock layer at the bottom of the foundation pile hole to form an expansion cavity, and place a circular expansion steel cage horizontally surrounding the bottom end of the foundation pile hole in the expansion cavity;
[0008] Step 4, placing the casing in the pile hole and making the lower end of the casing located at the center of the expanded steel cage, the plane position deviation between the center of the casing and the center of the pile hole should be no more than 50mm, and the inclination of the casing in the vertical direction should be no more than 1%, and then the end of the steel cage is sleeved with an isolation pipe and then vertically lowered to a specified height in the casing, the steel cage is located at the center of the casing and the upper and lower ends of the steel cage extend out of the casing by a certain length, wherein the top of the casing is 0.5m above the ground, and then the card plate is hooked on the top end of the casing to isolate the top of the steel cage from the top of the casing;
[0009] Step 5: Lower the air guide pipe in the casing to conduct reverse circulation to clean the hole. After withdrawing the air guide pipe, first fill the hole expansion cavity with an anti-seepage layer so that the anti-seepage layer can cover the hole expansion cavity and the pile bottom rock layer. When the anti-seepage layer is almost solidified, use C35 to pour underwater concrete in the casing. The first concrete pouring shall not exceed 15m 3 After the first pouring is completed, bury the measuring tube deep into the concrete, the burial depth shall not be less than 1.0m, and then continue pouring;
[0010] Step 6, divert the mud displaced by the poured concrete into the mud pool, and then transport the mud to a designated place for treatment to prevent environmental pollution; to ensure the strength of the concrete on the top of the pile, the top surface must exceed a certain height when the concrete is poured. When the designed elevation of the top surface of the poured concrete is more than 0.5m higher, stop pouring to form the final pile foundation.
[0011] The above scheme is further preferred, and the pile foundation construction method also includes: pulling out the casing after the final pile foundation is formed, if the height of the poured concrete pile foundation is greater than the height of the casing, using a grinding wheel to break the pile head at the designed elevation of the concrete pile foundation, after the casing is pulled out, the protective layer of concrete exceeding the pile head is chiseled off, and the main reinforcement of the steel cage is bent laterally to a close to horizontal position.
[0012] The above scheme is further preferred, in step 2, after the thickness of the sediment at the bottom of the pile hole is removed to be less than or equal to 5 cm, the hole cleaning is stopped, and a layer of newly prepared mud is injected, and the relative density of the injected mud is 0.05 g / cm 3 ~1.05g / cm 3 , viscosity is 19Pa·s, sand content is <2%. During the process of slag removal and hole cleaning, the mud height in the pile hole should always be kept above the groundwater level, and the mud ratio should be guaranteed to prevent the occurrence of hole collapse. After the mud is removed, the average value of the mud test at the bottom, middle and mouth of the hole should be close to that of the purified mud. When the thickness of the sediment at the bottom of the hole is less than or equal to 5cm, stop cleaning the hole.
[0013] The above scheme is further preferred, wherein the casing is rolled from a steel plate having a thickness of 12 mm to 30 mm and has a diameter of 200 cm to 370 cm.
[0014] The above scheme is further preferred, the wall protection mud must have the performance characteristics of fast hydration, strong slurry making ability, high viscosity, etc. The volume of the mud liquid is 1.5 to 3 times the volume of the foundation pile hole. The mud is mainly made of silty clay, bentonite, dispersant, and thickener. Among them, the weight fraction of bentonite is 4% to 15%, the viscosity of the mud is 18 to 30 Pa·s, and the density is 1.05g / cm 3 ~1.25g / cm 3 , wet water content <25%, pH value is 7.5-10, and the dispersant is methyl cellulose and / or sodium methyl cellulose.
[0015] The above scheme is further preferred, the colloid rate of the mud is ≥95%, the sand content is ≥3.5%, and the content of particles with a particle size of >0.1mm is <5.5%. According to the actual geological conditions and structural levels of the site, the adjustment and control of the mud concentration is strengthened to adapt to the actual geological conditions of the construction.
[0016] The above scheme is further preferred, the diameter of the expanded hole cavity formed by expanding the rock layer at the bottom of the foundation pile hole is at least 1.5 times larger than the foundation pile hole, and then the borehole inspection instrument is used to detect and measure the hole depth, hole diameter, and hole position. Two adjacent piles shall not be drilled or poured with concrete at the same time to avoid disturbing the hole wall and causing accidents of string holes and broken piles; after the pile foundation is drilled, the hole diameter and hole position must be measured, and the pile bottom rock, layer elevation and rock layer properties must be checked. Concrete can only be poured after confirming that they meet the design requirements. The allowable deviations of the foundation pile hole are as follows: the deviation of the center position of the pile group plane is less than 50mm; the axis deviation is less than 25mm; the inclination is less than 1 / 100; the sediment thickness is not more than 50mm; the bored piles should be strictly cleaned to ensure the quality of concrete and the bearing capacity of the pile foundation.
[0017] The above scheme is further preferred, and the pouring pressure when filling the anti-seepage layer slurry into the expanded hole cavity is 2 to 5 MPa, and the amount of the anti-seepage layer slurry poured is based on covering the expanded steel cage, so that the anti-seepage layer poured around the lower end of the foundation pile forms a sealed waterproof belt, and after solidification for 2 to 4 hours, the casing is appropriately lifted and then concrete is poured into the casing, thereby improving the anti-seepage performance of the pile foundation.
[0018] The above scheme is further preferred, the anti-permeability layer slurry is prepared from the following raw materials: 60-100 parts of white cement, 100-120 parts of black cement, 80-120 parts of fine aggregate sand and gravel, 100-150 parts of coarse aggregate sand and gravel, 20-50 parts of bentonite, 30-60 parts of polycarboxylic acid water reducer, 20-30 parts of foaming agent, 10-20 parts of graphene nanopowder, 10-15 parts of polypropylene fiber, and 8-15 parts of dispersion liquid; the fine aggregate sand and gravel is ≤5mm, and the coarse aggregate sand and gravel particle size is ≤25mm; wherein the preparation process of the anti-permeability layer slurry is as follows: weigh 60-100 parts of white cement, 100-120 parts of black cement, 80-120 parts of fine aggregate sand and gravel, 100-150 parts of coarse aggregate sand and gravel, and bentonite by weight. 20-50 parts, 30-60 parts of polycarboxylate water-reducing agent, 20-30 parts of foaming agent, 10-20 parts of graphene nanopowder, 10-15 parts of polypropylene fiber, and 8-15 parts of dispersion liquid; then white cement, black cement, fine aggregate sand and gravel, coarse aggregate sand and gravel, bentonite and polycarboxylate water-reducing agent are mixed uniformly to obtain a premix, graphene nanopowder and polypropylene fiber are added to the dispersion liquid in sequence for dispersion treatment for standby use, required water is added to the premix for repeated stirring, and during the stirring process, the foaming agent and the dispersion liquid are added in sequence for uniform stirring to obtain an anti-seepage body layer slurry, wherein the dispersion liquid is prepared by dissolving silane coupling agent KH-550 or 2-butenyltriethoxysilane and sodium methylenebisnaphthalenesulfonate in ethanol in a mass ratio of 1:2-4. After white cement, black cement and bentonite are mixed with each other, the setting time of concrete can be appropriately adjusted. After being dispersed in the dispersion liquid by graphene nanopowder and polypropylene fiber, the density and strength of concrete can be improved. When forming an impermeable sealing layer, the adhesion between the concrete and the casing can be reduced, the casing can be easily removed, cracks can be generated in the anti-permeability layer, the compressive strength and anti-permeability of concrete can be improved, and the foundation piles in the casing can be prevented from being infiltrated and eroded by water or other pollution.
[0019] In summary, the present invention adopts the above technical solution, and the present invention has the following technical effects:
[0020] The pile construction method of the present invention can improve the stability of the hole wall, prevent water seepage from the side wall of the pile hole, reduce the risk of hole wall collapse, and avoid the problem of surrounding soil squeezing and damaging the hole wall. During the construction process, it can ensure that the bridge foundation is of the same type, avoid uneven settlement caused by different foundation forms, improve the uniformity of settlement of adjacent pile foundations, effectively ensure the bearing capacity and seismic strength of the pile foundation, enhance the durability of the pile foundation, reduce the construction difficulty, shorten the construction period, and achieve high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a schematic diagram of the overall structure of a double-arm double-stage cap beam frame piece welding system of the present invention; DETAILED DESCRIPTION
[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.
[0023] Example 1: Combination Figure 1 As shown, according to a bridge foundation pile construction method of the present invention, the foundation pile construction method comprises the following steps:
[0024] Step 1: According to the design drawings and on-site geological survey, the construction site is excavated and leveled. After the site is leveled, a two-level slope protection wall with a ratio of at least 1:1.5 is built around the foundation piles, and a water retaining weir is set outside and at the root of the slope protection wall;
[0025] Step 2: Plan the range of the foundation piles within the scope of the construction site and mark the center of the piles, set up a mud pool around the foundation piles, and then use a rotary drilling rig to drill holes. When rotating and squeezing the drill bit, ensure that the drill bit is full of mud and then pull out the drill bit to replenish the mud. After the drilling is completed, remove the sediment at the bottom of the pile hole and keep drilling. Drill to the layer where the bottom expansion construction is expected to be carried out to form the foundation pile hole; the volume of the mud pool is 1.5 times the volume of the foundation pile hole. The mud made in the mud pool is mainly made of silty clay, bentonite, dispersant, and thickener, wherein the weight fraction of silty clay is 50%, the weight fraction of bentonite is 4%, the weight fraction of dispersant is 4%, the weight fraction of thickener is 6%, and the balance is water. The viscosity of the mud is 18Pa·s and the density is 1.05g / cm 3 , wet water volume <25%, pH value is 7.5, mud colloid rate ≥95%, sand content ≥3.5%, slurry making capacity ≥3.0L / kg, plasticity index >18, particle content of particle size >0.1mm <5.5%, dispersant is methyl cellulose. After the thickness of the sediment at the bottom of the pile hole is less than or equal to 5cm, stop cleaning the hole and inject a layer of newly prepared mud. The newly prepared mud is mainly made of silty clay, bentonite, dispersant, and thickener. The relative density of the mud is 0.05g / cm 3 , viscosity is 19Pa·s, sand content <2%
[0026] Step 3, after drilling the foundation pile hole, measure the hole depth, hole diameter, hole position, and check the elevation and rock properties of the pile bottom, then expand the rock layer at the bottom of the foundation pile hole to form an expansion cavity, and place a circular expansion steel cage horizontally surrounding the bottom end of the foundation pile hole in the expansion cavity; the diameter of the expansion cavity formed by expanding the rock layer at the bottom of the foundation pile hole is at least 1.5 times larger than the foundation pile hole, and then use a borehole inspection instrument to detect and measure the hole depth, hole diameter, and hole position;
[0027] Step 4, placing the casing in the pile hole and making the lower end of the casing located at the center of the expanded steel cage, the casing is made of 12mm thick steel plate and has a diameter of 200cm, and then the end of the steel cage is sleeved with an isolation pipe and then vertically lowered to a specified height in the casing, the steel cage is located in the center of the casing and the upper and lower ends of the steel cage extend out of the casing by a certain length, and then the clamping plate is hooked on the top end of the casing to isolate the top end of the steel cage from the top end of the casing;
[0028] Step 5: lower the air guide in the casing to conduct reverse circulation to clean the hole. After withdrawing the air guide pipe, first fill the expansion cavity with an anti-seepage layer so that the anti-seepage layer can cover the expansion cavity and the pile bottom rock layer, and wait until the anti-seepage layer is almost solidified; the pouring pressure when filling the expansion cavity with anti-seepage layer slurry is 2MPa, and the amount of anti-seepage layer slurry is based on covering the expanded steel cage, so that the anti-seepage layer poured around the lower end of the foundation pile forms a sealed waterproof belt, and after solidification for 2 hours, the casing is appropriately lifted and then concrete is poured into the casing; then C35 is used to pour underwater concrete into the casing, and the first concrete pouring does not exceed 15m 3 After the first pouring is completed, bury the measuring tube deep into the concrete, the burial depth shall not be less than 1.0m, and then continue pouring;
[0029] The anti-permeability layer is prepared from the following raw materials: 60 parts of white cement, 100 parts of black cement, 120 parts of fine aggregate sand and gravel, 100 parts of coarse aggregate sand and gravel, 20 parts of bentonite, 30 parts of polycarboxylic acid water reducer, 20 parts of foaming agent, 10 parts of graphene nano powder, 10 parts of polypropylene fiber, and 8 parts of dispersion liquid; the fine aggregate sand and gravel is ≤5mm, and the coarse aggregate sand and gravel particle size is ≤25mm;
[0030] Step 6, diverting the mud replaced by the poured concrete into the mud pool, and then transporting the mud to a designated place for treatment; preventing pollution to the environment; when the top surface design elevation of the poured concrete is higher than 0.5m, stopping the pouring to form the final pile foundation; in the present invention, after the final pile foundation is formed, the casing is pulled out, if the pile foundation height of the poured concrete is greater than the height of the casing, the pile head is broken by a grinding wheel at the design elevation of the concrete pile foundation, and after the casing is pulled out, the protective layer of concrete exceeding the pile head is chiseled off, and the main reinforcement of the steel cage is bent laterally to a near horizontal position.
[0031] Example 2: Combination Figure 1 As shown, according to a bridge foundation pile construction method of the present invention, the foundation pile construction method comprises the following steps:
[0032] Step 1: According to the design drawings and on-site geological survey, the construction site is excavated and leveled. After the site is leveled, a two-level slope protection wall with a ratio of at least 1:1.5 is built around the foundation piles, and a water retaining weir is set outside and at the root of the slope protection wall;
[0033] Step 2: Plan the range of the foundation piles within the scope of the construction site and mark the center of the piles, and set up a mud pool outside the foundation piles, then use a rotary drilling rig to drill holes, ensure that the drill bit is full of mud when rotating and squeezing the drill bit, then pull out the drill bit to replenish the mud, and remove the sediment at the bottom of the pile hole after the drilling is completed, keep drilling, and drill to the layer where the bottom expansion construction is expected to form a foundation pile hole; the volume of the mud pool is 3 times the volume of the foundation pile hole, and the mud made in the mud pool is mainly made of silty clay, bentonite, dispersant, and thickener, wherein the weight fraction of silty clay is 30%, the weight fraction of bentonite is 15%, the weight fraction of dispersant is 8%, the weight fraction of thickener is 10%, and the balance is water. The viscosity of the mud is 30Pa·s and the density is 1.25g / cm 3 , wet water volume <25%, pH value is 10, mud colloid rate ≥95%, sand content ≥3.5%, slurry making capacity ≥3.0L / kg, plasticity index >18, particle content of particle size >0.1mm <5.5%, dispersant is sodium methyl cellulose. After the thickness of the sediment at the bottom of the pile hole is less than or equal to 5cm, stop cleaning the hole and inject a layer of newly prepared mud. The newly prepared mud is mainly made of silty clay, bentonite, dispersant, and thickener. The relative density of the mud is 1.05g / cm 3 , viscosity is 19Pa·s, sand content <2%
[0034] Step 3, after drilling the foundation pile hole, measure the hole depth, hole diameter, hole position, and check the elevation and rock properties of the pile bottom, then expand the rock layer at the bottom of the foundation pile hole to form an expansion cavity, and place a circular expansion steel cage horizontally surrounding the bottom end of the foundation pile hole in the expansion cavity; the diameter of the expansion cavity formed by expanding the rock layer at the bottom of the foundation pile hole is at least 1.5 times larger than the foundation pile hole, and then use a borehole inspection instrument to detect and measure the hole depth, hole diameter, and hole position;
[0035] Step 4, placing the casing in the pile hole and making the lower end of the casing located at the center of the expanded steel cage, the casing is made of 30mm thick steel plate and rolled into a diameter of 370cm, and then the end of the steel cage is sleeved with an isolation pipe and then vertically lowered to a specified height in the casing, the steel cage is located in the center of the casing and the upper and lower ends of the steel cage extend out of the casing by a certain length, and then the clamping plate is hooked on the top end of the casing to isolate the top end of the steel cage from the top end of the casing;
[0036] Step 5: lower the air guide in the casing to conduct reverse circulation to clean the hole. After withdrawing the air guide pipe, first fill the expansion cavity with an anti-seepage layer so that the anti-seepage layer can cover the expansion cavity and the pile bottom rock layer, and wait until the anti-seepage layer is almost solidified; the pouring pressure when filling the expansion cavity with anti-seepage layer slurry is 5MPa, and the amount of anti-seepage layer slurry is based on covering the expanded steel cage, so that the anti-seepage layer poured around the lower end of the foundation pile forms a sealed waterproof belt. After solidification for 4 hours, the casing is properly lifted and concrete is poured into the casing; then C35 is used to pour underwater concrete into the casing, and the first concrete pouring does not exceed 15m 3 After the first pouring is completed, bury the measuring tube deep into the concrete, the burial depth shall not be less than 1.0m, and then continue pouring;
[0037] The anti-permeability layer is prepared from the following raw materials: 100 parts of white cement, 120 parts of black cement, 80 parts of fine aggregate sand and gravel, 150 parts of coarse aggregate sand and gravel, 50 parts of bentonite, 60 parts of polycarboxylic acid water reducer, 30 parts of foaming agent, 20 parts of graphene nano powder, 15 parts of polypropylene fiber, and 15 parts of dispersion liquid; the particle size of fine aggregate sand and gravel is ≤5mm, and the particle size of coarse aggregate sand and gravel is ≤25mm;
[0038] Step 6, divert the mud replaced by the poured concrete into the mud pool, and then transport the mud to a designated place for treatment; prevent pollution to the environment; when the top surface design elevation of the poured concrete is higher than 0.5m, stop pouring to form the final pile foundation; in the present invention, after the final pile foundation is formed, the casing is pulled out. If the pile foundation height of the poured concrete is greater than the height of the casing, the pile head is broken by a grinding wheel at the design elevation of the concrete pile foundation. After the casing is pulled out, the protective layer of concrete beyond the pile head is chiseled off, and the main reinforcement of the steel cage is bent laterally close to the horizontal position.
[0039] Example 3: Combination Figure 1 As shown, according to a bridge foundation pile construction method of the present invention, the foundation pile construction method comprises the following steps:
[0040] Step 1: According to the design drawings and on-site geological survey, the construction site is excavated and leveled. After the site is leveled, a two-level slope protection wall with a ratio of at least 1:1.5 is built around the foundation piles, and a water retaining weir is set outside and at the root of the slope protection wall;
[0041] Step 2: Plan the range of the foundation piles within the scope of the construction site and mark the center of the piles, set up a mud pool around the foundation piles, and then use a rotary drilling rig to drill holes. When rotating and squeezing the drill bit, ensure that the drill bit is full of mud and then pull out the drill bit to replenish the mud. After the drilling is completed, remove the sediment at the bottom of the pile hole, keep drilling, and drill to the layer where the bottom expansion construction is expected to be carried out to form the foundation pile hole; the volume of the mud pool is 1.5 to 3 times the volume of the foundation pile hole. The mud made in the mud pool is mainly made of silty clay, bentonite, dispersant, and thickener, wherein the weight fraction of silty clay is 40%, the weight fraction of bentonite is 10%, the weight fraction of dispersant is 6%, the weight fraction of thickener is 8%, and the balance is water. The viscosity of the mud is 25Pa·s and the density is 1.15g / cm 3 , wet water volume <25%, pH value is 8, mud colloid rate ≥95%, sand content ≥3.5%, slurry making capacity ≥3.0L / kg, plasticity index >18, particle content of particle size >0.1mm <5.5%, dispersant is methyl cellulose and methyl cellulose sodium. After the thickness of the sediment at the bottom of the pile hole is less than or equal to 5cm, stop cleaning the hole and inject a layer of newly prepared mud. The newly prepared mud is mainly made of silty clay, bentonite, dispersant, and thickener. The relative density of the mud is 0.8g / cm 3 , viscosity is 19Pa·s, sand content is <2%;
[0042] Step 3, after drilling the foundation pile hole, measure the hole depth, hole diameter, hole position, and check the elevation and rock properties of the pile bottom, then expand the rock layer at the bottom of the foundation pile hole to form an expansion cavity, and place a circular expansion steel cage horizontally surrounding the bottom end of the foundation pile hole in the expansion cavity; the diameter of the expansion cavity formed by expanding the rock layer at the bottom of the foundation pile hole is at least 1.5 times larger than the foundation pile hole, and then use a borehole inspection instrument to detect and measure the hole depth, hole diameter, and hole position;
[0043] Step 4, placing the casing in the pile hole and making the lower end of the casing located at the center of the expanded steel cage, the casing is made of 20mm thick steel plate and rolled into a diameter of 180cm, and then the end of the steel cage is sleeved with an isolation pipe and then vertically lowered to a specified height in the casing, the steel cage is located in the center of the casing and the upper and lower ends of the steel cage extend out of the casing by a certain length, and then the clamping plate is hooked on the top end of the casing to isolate the top end of the steel cage from the top end of the casing;
[0044] Step 5: lower the air guide in the casing to conduct reverse circulation to clean the hole. After withdrawing the air guide pipe, first fill the expansion cavity with an anti-seepage layer so that the anti-seepage layer can cover the expansion cavity and the pile bottom rock layer, and wait until the anti-seepage layer is almost solidified; the pouring pressure when filling the expansion cavity with anti-seepage layer slurry is 4MPa, and the amount of anti-seepage layer slurry is based on covering the expanded steel cage, so that the anti-seepage layer poured around the lower end of the foundation pile forms a sealed waterproof belt. After solidification for 3 hours, the casing is properly lifted and concrete is poured into the casing; then C35 is used to pour underwater concrete into the casing, and the first concrete pouring does not exceed 15m 3 After the first pouring is completed, the measuring tube is deeply buried in the concrete, the burial depth shall not be less than 1.0m, and then the pouring is continued; the anti-permeability layer is prepared from the following raw materials: 80 parts of white cement, 110 parts of black cement, 100 parts of fine aggregate sand and gravel, 120 parts of coarse aggregate sand and gravel, 40 parts of bentonite, 40 parts of polycarboxylic acid water reducer, 25 parts of foaming agent, 15 parts of graphene nano powder, 12 parts of polypropylene fiber, and 10 parts of dispersion liquid; the fine aggregate sand and gravel ≤5mm, and the coarse aggregate sand and gravel particle size ≤25mm;
[0045] Step 6, diverting the mud replaced by the poured concrete into the mud pool, and then transporting the mud to a designated place for treatment; preventing pollution to the environment; when the top surface design elevation of the poured concrete is higher than 0.5m, stopping the pouring to form the final pile foundation; in the present invention, after the final pile foundation is formed, the casing is pulled out, if the pile foundation height of the poured concrete is greater than the height of the casing, the pile head is broken by a grinding wheel at the design elevation of the concrete pile foundation, and after the casing is pulled out, the protective layer of concrete exceeding the pile head is chiseled off, and the main reinforcement of the steel cage is bent laterally to a near horizontal position.
[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A bridge foundation pile construction method, characterized in that: The pile construction method comprises the following steps: Step 1: According to the design drawings and on-site geological survey, the construction site is excavated and leveled. After the site is leveled, a two-level slope protection wall with a ratio of at least 1:1.5 is built around the foundation piles, and a water retaining weir is set outside and at the root of the slope protection wall; Step 2: Plan the range of the foundation piles within the scope of the construction site and mark the center of the piles, and set up a mud pool outside the foundation piles. Then use a rotary drilling rig to drill holes. When rotating and squeezing the drill bit, ensure that the drill bit is full of mud, then pull out the drill bit to replenish the mud. After drilling, remove the sediment at the bottom of the pile hole, keep drilling, and drill to the expected layer for bottom expansion construction to form the foundation pile hole; Step 3, after drilling the foundation pile hole, measure the hole depth, hole diameter, hole position, and check the elevation and rock properties of the pile bottom, then expand the rock layer at the bottom of the foundation pile hole to form an expansion cavity, and place a circular expansion steel cage horizontally surrounding the bottom end of the foundation pile hole in the expansion cavity; Step 4, placing the casing in the pile hole and making the lower end of the casing located at the center of the enlarged steel cage, then putting an isolation tube on the end of the steel cage and vertically lowering it to a specified height in the casing, the steel cage is located at the center of the casing and the upper and lower ends of the steel cage extend out of the casing by a certain length, and then using a clamping plate hook to hang on the top end of the casing, so that the top of the steel cage is isolated from the top of the casing; Step 5: Lower the air guide pipe in the casing to conduct reverse circulation to clean the hole. After withdrawing the air guide pipe, first fill the hole expansion cavity with an anti-seepage layer so that the anti-seepage layer can cover the hole expansion cavity and the pile bottom rock layer. When the anti-seepage layer is almost solidified, use C35 to pour underwater concrete in the casing. The first concrete pouring shall not exceed 15m 3 After the first pouring is completed, bury the measuring tube deep into the concrete, the burial depth shall not be less than 1.0m, and then continue pouring; Step 6, divert the mud displaced by the poured concrete into the mud pool, and then transport the mud to a designated place for treatment. When the top surface design elevation of the poured concrete is more than 0.5m higher, stop pouring to form the final pile foundation.
2. A bridge foundation pile construction method according to claim 1, characterized in that: The pile foundation construction method also includes: pulling out the casing after the final pile foundation is formed, if the height of the poured concrete pile foundation is greater than the height of the casing, using a grinding wheel to break the pile head at the designed elevation of the concrete pile foundation, after the casing is pulled out, chiseling off the protective layer of concrete exceeding the pile head, and bending the main reinforcement of the steel cage laterally to a close to horizontal position.
3. A bridge foundation pile construction method according to claim 1, characterized in that: In step 2, after the thickness of the sediment at the bottom of the pile hole is less than or equal to 5 cm, the hole cleaning is stopped and a layer of newly prepared mud is injected. The relative density of the injected mud is 0.05 g / cm 3 ~1.05g / cm 3 , viscosity is 19Pa·s, and sand content is <2%.
4. A bridge foundation pile construction method according to claim 1, characterized in that: The casing is rolled from a steel plate with a thickness of 12 mm to 30 mm and has a diameter of 200 cm to 370 cm.
5. A bridge foundation pile construction method according to claim 1, characterized in that: The volume of the mud liquid is 1.5 to 3 times the volume of the foundation pile hole. The mud is mainly made of silty clay, bentonite, dispersant, and thickener. Among them, the weight fraction of bentonite is 4% to 15%, the viscosity of the mud is 18 to 30 Pa·s, and the density is 1.05 g / cm 3 ~1.25g / cm 3 , wet water content <25%, pH value is 7.5-10, and the dispersant is methyl cellulose and / or sodium methyl cellulose.
6. A bridge foundation pile construction method according to claim 5, characterized in that: The colloid rate of the mud is ≥95%, the sand content is ≥3.5%, and the content of particles with a particle size of >0.1 mm is <5.5%.
7. A bridge foundation pile construction method according to claim 1, characterized in that: The diameter of the expanded hole cavity formed by expanding the rock formation at the bottom of the pile hole is at least 1.5 times that of the pile hole, and then a borehole inspection instrument is used to detect and measure the hole depth, hole diameter and hole position.
8. A bridge foundation pile construction method according to claim 1, characterized in that: The pouring pressure when filling the anti-seepage layer slurry into the expanded cavity is 2 to 5 MPa. The amount of anti-seepage layer slurry poured is based on covering the expanded steel cage, so that the anti-seepage layer poured around the lower end of the foundation pile forms a sealed waterproof belt. After solidification for 2 to 4 hours, the casing is properly lifted and then concrete is poured into the casing.
9. A bridge foundation pile construction method according to claim 8, characterized in that: The anti-seepage layer is prepared from the following raw materials: 60-100 parts of white cement, 100-120 parts of black cement, 80-120 parts of fine aggregate sand and gravel, 100-150 parts of coarse aggregate sand and gravel, 20-50 parts of bentonite, 30-60 parts of polycarboxylic acid water reducer, 20-30 parts of foaming agent, 10-20 parts of graphene nano powder, 10-15 parts of polypropylene fiber, and 8-15 parts of dispersion liquid; wherein the fine aggregate sand and gravel is ≤5mm, and the particle size of the coarse aggregate sand and gravel is ≤25mm.