Bridge pile foundation construction method suitable for inclined rock stratum

Abstract

The invention relates to the technical field of bridge pile foundation construction, in particular to a bridge pile foundation construction method suitable for an inclined rock stratum. A pile hole is drilled through the first drill bit, when inclined rock is encountered in the drilling process, the guide pipe is used as a limit, soil layer side reinforcement is conducted through concrete, the guide pipe is pre-buried in the concrete, a small hole is drilled through the second drill bit under the limit effect of the guide pipe, and the inclined rock stratum at the bottom of the concrete is drilled through at a time; the overall strength of the inclined rock is reduced; under the condition that the overall strength of the inclined rock is reduced, the first drill bit with the large diameter continues to conduct downward drilling construction on the section of the concrete, at the moment, the possibility that the first drill bit deflects when encountering part of the structure of the inclined rock stratum is small, it can be guaranteed that the whole section of the first drill bit is embedded into the inclined rock stratum, the error of the pile hole perpendicularity is reduced, and the construction efficiency is improved. And the inclination of the pile body of the pile foundation can be controlled within the allowable error range, so that the pile forming quality and the pile bearing capacity are improved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge pile foundation construction, in particular to a bridge pile foundation construction method suitable for inclined rock strata. Background Art

[0002] When constructing railway projects in dangerous mountainous areas, it is inevitable to use bridge structures with larger spans to cross canyon sections. Due to the large span of the bridge and the heavy railway load, the bridge needs to use pile foundations with good bearing capacity and strong adaptability. The verticality of the pile foundation has an important impact on its own vertical bearing capacity. At present, pile foundations are generally constructed using rotary drilling or impact drilling. The drill bit size of the rotary drilling or impact drilling matches the pile diameter, and the pile hole is formed in one step. However, in steep slopes in mountainous areas, the geological structure is complex, the rock type and facies vary greatly, the engineering geological properties of the rock and soil are poor, and the various geological contents such as strata, lithology, facies, and structure vary dramatically. In the early survey stage, it is difficult to accurately explore the distribution of strata, which makes it very easy to encounter inclined rock strata during construction. If inclined rock strata are encountered during the drilling process, such as Figure 1 As shown in the figure, in the same pile hole, due to the high rock strength on the inclined rock side and the low strength on the soil layer side, it is difficult to drill a hole on the high-strength rock layer side during conventional pile foundation construction. The drill bit follows the rock surface and tends to tilt toward the low-strength soil layer side, resulting in the inclination of the pile foundation drilling hole not meeting the requirements and being difficult to repair.

[0003] In order to solve the problem of drilling inclination caused by the large strength difference at different positions of the pile hole, the commonly used method is to fill the pile hole with high-strength stone or pour concrete after encountering inclined rock, so as to improve the strength of the soil layer side of the inclined rock section, make the strength of the soil layer side as consistent as possible with the strength of the inclined rock side, reduce the strength difference at different positions of the pile hole, and then drill into the inclined rock stratum to a certain depth, so as to gradually pass through the inclined rock stratum. This method requires repeated filling and drilling many times, firstly, the construction cost is high, and secondly, the construction period is long; if encountering extremely high-strength granite and other strata, and the stratum inclination angle is large, the strength of the filled stone or concrete is still relatively low compared with it, and when the drilling encounters large-angle inclined rock, the drill bit will still tilt to the low-strength side, which will also cause the pile hole to deviate. If the method of manual hole digging and blasting is adopted, firstly, when the depth of inclined rock is deep or the groundwater level is high, the risk of manual operation is extremely high; secondly, the blasting construction has a great impact on the adjacent pile foundations or existing buildings; thirdly, the bored holes of the pile foundations that have been constructed need to have mud walls, and it is difficult for manual operation in the mud.

[0004] Therefore, it is necessary to study a mechanized construction method for bridge pile foundations in large-angle, high-strength rock formations to reduce the amount of filling during construction, improve construction efficiency, and solve the problem that the inclination of the pile foundation does not meet the requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a bridge pile foundation construction method suitable for inclined rock strata, which can ensure the verticality of the pile foundation, in view of the problem that in the prior art, when drilling pile holes for pile foundations, the drilling hole is prone to tilt if an inclined rock strata is encountered, thereby affecting the verticality of the pile foundation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A bridge pile foundation construction method suitable for inclined rock strata comprises the following steps: S1: using a first drill bit to drill into the inclined rock layer at the pile position, so as to expose the inclined rock layer and form a pile bottom section in the drill hole; S2: lowering a plurality of guide tubes into the borehole, making each of the guide tubes contact the pile bottom section respectively, and temporarily fixing all the guide tubes, wherein the bottom of the guide tube is wrapped with a foam casing, and the inclined rock layer corresponds to the position of the guide tube; S3: pouring concrete into the drilled hole, wherein the concrete is used to fix all the guide pipes, and the concrete is not higher than the top of the foam sleeve; S4: After the strength of the concrete meets the requirement, lower the second drill bit through the guide tube, and use the second drill bit to drill holes in the inclined rock until the inclined rock stratum is penetrated; S5: Pull out the guide tube and continue drilling construction using the first drill bit.

[0007] In the bridge pile foundation construction method provided by the present invention, a pile hole is drilled by a first drill bit. When an inclined rock is encountered during the drilling process, a guide tube is set to limit the second drill bit, and the bottom end of the guide tube is fixed by concrete and the soil layer side is reinforced. The guide tube is pre-buried in the concrete, and a second drill bit is used to drill a small hole with the guide tube as a guide, and the inclined rock stratum at the bottom of the concrete is drilled through at one time to reduce the overall strength of the inclined rock. When the overall strength of the inclined rock has been reduced, a large-diameter first drill bit is used to continue drilling downward on the section of the concrete. At this time, the first drill bit is less likely to deflect when encountering an inclined rock stratum again, and the first drill bit can be fully embedded in the inclined rock layer, thereby reducing the error in the verticality of the pile hole and controlling the inclination of the pile body of the pile foundation within the allowable error range, thereby improving the quality of the pile and the bearing capacity of the pile.

[0008] During the drilling process, the thinner and longer the drill bit and drill rod are, the easier it is to bend and deform, and the stability of the drill bit at the end is worse. There is a phenomenon that the drill rod drives the drill bit to swing. If the strength difference of the rock formation is large, the drill bit is easy to deviate to the side with smaller strength during drilling, so that it is difficult to drill the target rock formation. Therefore, in this scheme, when the first drill bit drills into the inclined rock layer to expose the inclined rock layer, a guide tube is used to limit the second drill bit for drilling a small hole, so that the second drill bit works along the axial direction of the guide tube, and the guide tube can directly contact the inclined rock layer at the bottom of the pile, reducing the free length of the drill rod and drill bit (that is, the unrestricted length, which is the overall length of the drill rod and drill bit in the free state; when a guide tube is provided, it is the length extending from the guide tube), ensuring that the second drill bit is fully embedded in the inclined rock layer for structural decomposition; at the same time, in order to ensure the structural stability of the guide tube, it needs to be temporarily fixed when the guide tube is positioned and placed, and then pulled out after the inclined rock drilling hole is decomposed by the second drill bit to facilitate the first drilling hole to continue the pile hole construction. Based on this, this solution wraps a foam sleeve at the bottom of the guide pipe and pours a certain depth of concrete in the borehole, using concrete to further fix the guide pipe. The foam sleeve can isolate the guide pipe from the subsequent concrete pouring, making it easier to pull out the guide pipe. The above-mentioned bridge pile foundation construction method is used to construct the pile foundation, with high construction efficiency, no need for repeated backfilling and drilling, low construction investment and loss, and is suitable for construction conditions where drilling deviation occurs when encountering large inclination angles and high-strength rock formations during the drilling process.

[0009] As a preferred embodiment of the present invention, in step S2, the guide tube is fixedly connected to the steel cage through at least one layer of steel mesh, the steel cage is used to support the drilling hole, the lowered position of the steel cage in the drilling hole is not lower than the top position of the foam sleeve, and the steel mesh is used to position and penetrate the guide tube.

[0010] In this solution, the guide tube is fixedly connected to the steel cage through at least one layer of steel mesh, and the steel cage is used to support the borehole and play a role in protecting the wall. At the same time, the guide tube can be positioned and fixed by the steel mesh; at the same time, when the steel cage is lowered to a position not lower than the top of the foam casing, the bottom of the steel cage cannot completely contact the entity and is in a suspended state. At this time, the steel cage can be supported on the inclined rock layer through the fixed guide tube to achieve self-stabilization. Correspondingly, the lowering position of the steel cage in the borehole is set not lower than the top of the foam casing, so that the subsequent pouring of concrete has no effect on the steel cage, which facilitates the subsequent pulling out of the steel cage together with the guide tube. The pile foundation steel cage is used as the support of the guide tube, which has good stability and can be reused, and can achieve the effect of green environmental protection and good economic benefits.

[0011] In this scheme, the steel cage can be placed first, and then the guide tube can be positioned and inserted, and the fixed connection can be performed after the lowering position of the guide tube is determined in real time; the lengths of several guide tubes can also be determined in advance according to the position and direction of the inclined rock layer, and the steel cage and the guide tube can be fixed and then lowered into the drill hole together. The steel cage and the guide tube can be either integrally connected or detachably connected, and the implementation method is not limited to the above examples.

[0012] As a preferred solution of the present invention, in step S5, the steel cage and the guide tube are pulled out together to facilitate subsequent drilling; after the hole is formed, the steel cage is used as a permanent stress-bearing steel cage of the pile foundation, thereby achieving multiple uses of one object and reducing construction losses.

[0013] As a preferred solution of the present invention, a layer of the steel mesh is arranged every 0.7m-1.2m along the length direction of the steel cage, and each layer of the steel mesh is fixedly connected to the guide tube. The guide tube has good stability, which is conducive to the drilling construction of the second drill bit.

[0014] As a preferred solution of the present invention, the top surface of the guide tube is flush with the ground to facilitate lowering the second drill bit.

[0015] As a preferred embodiment of the present invention, the top surface of the concrete is arranged higher than the top of the inclined rock layer, so that when pouring concrete, it can fill the hollowed-out position on the soil layer side caused by the inclined drilling of the first drill bit due to encountering the inclined rock layer, thereby strengthening the bottom structural strength of the soil layer side of the borehole, which is beneficial to the stability of the hole wall and subsequent drilling construction.

[0016] As a preferred solution of the present invention, the inner diameter of the guide tube is 8cm-15cm, which is convenient for adapting to the lowering of a small diameter drill bit.

[0017] As a preferred solution of the present invention, the foam sleeve covers the bottom port of the guide tube to prevent concrete from entering the guide tube and reduce the workload of the second drill bit.

[0018] As a preferred solution of the present invention, the length of the foam sleeve is greater than the slope height of the inclined rock, ensuring that the top position of the foam sleeve on each guide tube is higher than the top position of the inclined rock surface; further preferably, the foam sleeve is 2m-3m long, so that the foam sleeve can be uniformly customized with a wide range of applications, and different lengths can be used according to actual working conditions to reduce material loss.

[0019] As a preferred solution of the present invention, the first drill bit is an impact drill or a rotary drill.

[0020] As a preferred solution of the present invention, the second drill bit is a spiral drill.

[0021] As an alternative to the present invention, step S1 can be replaced by using the first drill bit to drill at the pile position to a position above the top of the inclined rock layer, stopping drilling, and forming a section in the pile position. This solution is suitable for situations where the inclination of the stratum has been verified during the survey.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The bridge pile foundation construction method provided by the present invention can adapt to the construction conditions where drilling deviation occurs when encountering large-angle, high-strength rock formations during the drilling process. This method can drill through the inclined rock formation in one go, with high construction efficiency, small construction losses and good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the state in which the drill bit deviates when encountering inclined rock formations during drilling; Figure 2 It is the plan layout of the guide tube and the steel cage; Figure 3 is a layout diagram of the steel cage and the guide tube in the pile foundation borehole in Example 1; Figure 4 is a vertical layout diagram of the foam sleeve of the guide tube jacket in Example 1; Figure 5 This is a construction state diagram of pouring concrete after the steel cage and guide pipe are positioned in Example 1; Figure 6 is a schematic diagram of the structure after the pile foundation is drilled in Example 1; Figure 7 is a layout diagram of the steel cage and the guide tube in the pile foundation borehole in Example 2; Figure 8 This is a construction status diagram of pouring concrete after the reinforcement cage and guide pipe are positioned in Example 2.

[0024] Icons: 1- inclined rock layer; 2- guide pipe; 3- foam casing; 4- steel cage; 5- steel mesh; 6- concrete. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0026] 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 in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1 This embodiment provides a bridge pile foundation construction method suitable for inclined rock formations, comprising the following steps: S1: Use a large-diameter first drill bit to drill a hole at the pile position. When the pile foundation drilling hole encounters inclined rock, the inclined rock layer 1 (i.e., the top surface of the inclined rock) is exposed, thereby forming a pile bottom section in the drill hole.

[0028] S2: Figure 2-Figure 4 As shown, a steel cage 4 and several guide tubes 2 matching the pile diameter are placed into the borehole. The outer side of the tube body within the range of 2-3m at the bottom of the guide tube 2 is wrapped with a foam sleeve 3 to isolate the guide tube 2 from the subsequently poured concrete 6, so as to facilitate the subsequent pulling out of the guide tube 2. The bottom of each guide tube 2 contacts the bottom of the pile, that is, the inclined rock layer 1. All guide tubes 2 are arranged inside the steel cage 4 and temporarily fixed. In this embodiment, each guide tube 2 is mainly used to contact the inclined rock layer 1 to accurately locate the drilling hole on the inclined rock surface; the spacing of the guide tubes 2 is arranged at about 50cm to effectively decompose the inclined rock and achieve a honeycomb effect. The guide tube 2 uses a seamless steel pipe with a diameter of about 10cm, and is positioned in the steel cage 4 by welding steel bars every about 1m in the length direction of the steel cage 4.

[0029] As an implementable method of this embodiment, if an inclined rock stratum is not discovered during the survey and is discovered during the pile foundation drilling construction, and the borehole has already tilted and deviated, and the elevation of the bottom of the borehole is different (the borehole is tilted toward the softer side of the stratum), the inclination of the borehole can be measured first, and the length of the guide tube 2 and the length of the foam sleeve 3 can be calculated according to the plane position of the guide tube 2, and the guide tube 2 and the steel cage 4 can be fixed and lowered together; or the steel cage 4 can be lowered first, and then the guide tube 2 can be lowered in turn, and after the bottom of the guide tube 2 contacts the inclined rock surface, the required length of the guide tube 2 and the foam sleeve 3 is measured, and then the guide tube 2 is pulled out to cut the appropriate length, and the foam sleeve 3 is installed, and the top of the guide tube 2 is fixed to the steel cage 4 after being lowered, and foam sleeves 3 of different lengths are customized to reduce material loss.

[0030] As an implementable embodiment of this embodiment, at least one layer of steel mesh 5 composed of a plurality of positioning steel bars crisscrossed and integrated can be pre-set on the cross section of the steel cage 4. The steel mesh 5 includes a plurality of mesh holes through which the guide tube 2 can be inserted, so as to be used for rapid positioning and fixing of the guide tube 2.

[0031] The steel cage 4 can not only be used to support the borehole and protect the wall, but also can position and fix the guide tube 2 through the steel mesh 5; at the same time, when the steel cage 4 is lowered to a position not lower than the top of the foam sleeve 3, the bottom of the steel cage 4 cannot completely contact the entity and is in a suspended state. At this time, the steel cage 4 can be supported on the inclined rock layer through the fixed guide tube 2 to achieve self-stabilization. Correspondingly, the lowered position of the steel cage 4 in the borehole is set not lower than the top of the foam sleeve 3, so that the subsequent pouring of concrete 6 has no effect on the steel cage 4, which is convenient for the subsequent steel cage 4 to be pulled out together with the guide tube 2; in this embodiment, it is preferred to make the bottom of the steel cage 4 flush with the top of the foam sleeve 3. The pile foundation steel cage 4 is used as the support of the guide tube 2, which has good stability and can be reused, and can achieve the effect of green environmental protection and good economic benefits.

[0032] When arranging the guide pipe 2, it is preferred to set a hole position at the highest point of the inclined rock layer 1, and set multiple hole positions symmetrically along the circumference of the pile diameter with the highest point of the inclined rock layer 1 in the pile hole as the center, and also set multiple hole positions in a dot matrix in the middle of the pile hole to form honeycomb hole positions on the inclined surface of the inclined rock layer 1.

[0033] S3: Figure 5 As shown, after the steel cage 4 with the positioned guide tube 2 is placed in the pile foundation borehole, the pile foundation underwater concrete 6 is poured, and the concrete 6 is poured to a height of 2m above the top of the inclined rock surface to achieve fixed positioning of the guide tube 2; wherein, the pouring height of the underwater concrete 6 should not exceed the height of the foam sleeve 3 at the bottom of the guide tube 2.

[0034] S4: After the strength of the concrete 6 to be poured meets the requirements, a second drill bit with a small diameter is lowered through the guide tube 2, and the second drill bit is used to decompose the inclined rock drilling hole, and the entire inclined rock is drilled into a honeycomb shape, thereby reducing the overall strength of the inclined rock. The drilling depth is until the inclined rock stratum is drilled through, and the construction efficiency is high; S5: After the drilling of the guide tube 2 is completed, the steel cage 4 and the guide tube 2 supported by it are pulled out together, and then the original first drill bit is used for drilling construction; in this process, if the first drill bit encounters an inclined rock layer 1 and the drilling is tilted, resulting in the bottom part of the soil layer being hollowed out, at this time, it has been filled and reinforced with concrete 6, and the borehole wall is stable. The hole state is as follows: Figure 6 shown.

[0035] After cleaning, the steel cage 4 can be used as a permanent stress-bearing steel cage 4 of the pile foundation; the foam wrapped around the guide tube 2 will float on the mud surface of the pile hole after the first drill bit is constructed due to its light weight, and can be smoothly discharged through the mud pumping during construction.

[0036] In step S2 of this embodiment, the top surface of the guide tube 2 is preferably set flush with the ground to facilitate lowering the second drill bit; the foam sleeve 3 not only covers the outer side of the tube body, but also covers the bottom port of the guide tube 2 to prevent concrete 6 from entering the guide tube 2, thereby reducing the drilling workload of the second drill bit. The first drill bit can be an impact drill or a rotary drill, and the second drill bit is preferably a small-diameter spiral drill.

[0037] In the above-mentioned bridge pile foundation construction method, by using the first drill bit to drill into the inclined rock layer 1 at the pile position to expose the inclined rock layer 1, the guide tube 2 can be directly in contact with the inclined rock layer 1, reducing the distance between the guide tube 2 and the inclined rock, so that when the second drill bit is used to drill holes later, the swing amplitude of the drill rod drill bit can be reduced under the limiting effect of the guide tube 2, so that the second drill bit can better concentrate on drilling holes in the inclined rock. The method uses a first drill bit to drill a pile hole. When encountering inclined rock during the drilling process, a guide tube 2 is set to limit the second drill bit, and the bottom end of the guide tube 6 is fixed and the soil layer side is reinforced by concrete 6. The guide tube 2 is pre-buried in the concrete 6, and a second drill bit is used to drill a small hole under the limiting effect of the guide tube 2, and the inclined rock stratum at the bottom of the concrete 6 is drilled at one time, thereby reducing the overall strength of the inclined rock. When the overall strength of the inclined rock has been reduced, a large-diameter first drill bit is used to continue drilling downward on the section of the concrete 6. At this time, the first drill bit is less likely to deflect when encountering an inclined rock stratum again, and the first drill bit can be fully embedded in the inclined rock layer 1, thereby reducing the error of the verticality of the pile hole, so that the inclination of the pile body of the pile foundation can be controlled within the allowable error range, thereby improving the quality of the pile and the bearing capacity of the pile.

[0038] During the drilling process, the thinner and longer the drill bit and the drill rod are, the easier it is to bend and deform, and the stability of the drill bit at the end is worse. There is a phenomenon that the drill rod drives the drill bit to swing. If the strength difference of the rock formation is large, the drill bit is easy to deviate to the side with smaller strength during drilling, so that it is difficult to drill the target rock formation. Therefore, in this scheme, when the first drill bit drills into the inclined rock layer 1 to expose the inclined rock layer 1, the guide tube 2 is used to limit the second drill bit for drilling a small hole, so that the second drill bit works along the axial direction of the guide tube 2, and the guide tube 2 directly contacts the inclined rock layer 1 at the bottom of the pile, reducing the free length of the drill rod and the drill bit (that is, the unrestricted length, which is the overall length of the drill rod and the drill bit in the free state; when the guide tube 2 is provided, it is the length extending from the guide tube 2), ensuring that the second drill bit is fully embedded in the inclined rock layer 1 for structural decomposition; at the same time, in order to ensure the structural stability of the guide tube 2, it needs to be temporarily fixed when the guide tube 2 is positioned and placed, and then pulled out after the inclined rock drilling hole is decomposed by the second drill bit to facilitate the first drilling hole to continue the pile hole construction. Based on this, this solution wraps a foam sleeve 3 at the bottom of the guide tube 2 and pours a certain depth of concrete 6 in the borehole, and uses the concrete 6 to further fix the guide tube 2. The foam sleeve 3 can isolate the guide tube 2 from the subsequently poured concrete 6, which is convenient for pulling out the guide tube 2 later; at the same time, the backfilled concrete 6 is set higher than the top of the inclined rock layer 1, and the hollowed-out position on the soil layer side caused by the inclined drilling of the first drill bit due to the inclined rock layer 1 is filled in time, which strengthens the bottom structural strength of the soil layer side of the borehole, and is conducive to the stability of the hole wall and subsequent drilling construction. The above-mentioned bridge pile foundation construction method is used to construct pile foundations, with high construction efficiency, no need for repeated backfilling and drilling, small construction investment and loss, and is suitable for the construction conditions where drilling deviation occurs when encountering large inclination angles and high-strength rock formations during the drilling process.

[0039] Example 2 This embodiment provides a bridge pile foundation construction method suitable for inclined rock formations, such as Figure 7 , Figure 8 As shown, compared with Example 1, the difference of this embodiment mainly lies in the difference in the initial drilling position of the first drill bit at the pile position, which is suitable for the situation where the inclination of the formation has been verified during the survey. Specifically, this embodiment includes the following steps: S1: After drilling to the top of the inclined rock layer 1 at the pile position using the first drill bit, the drilling is stopped, and a section is formed in the pile position.

[0040] S2: lower a steel cage 4 and several guide tubes 2 matching the pile diameter into the borehole, the guide tubes 2 are fixedly connected to the steel cage 4 by steel bars, the bottom of the guide tubes 2 exceeds the steel cage 4 by 2-3m, and the bottom of the guide tubes 2 is wrapped with 2-3m of foam casing 3; because the inclined rock layer has not yet been constructed, the bottom of the borehole is horizontal at this time, and is supported at the bottom of the borehole by the guide tubes 2 with foam casing 3. In this embodiment, since the bottom elevation of the borehole is basically the same, the guide tubes 2 can be fixed to the steel cage 4 before lowering.

[0041] S3: Pour concrete 6 into the borehole so that the concrete 6 is a certain distance above the top of the inclined rock layer 1. At the same time, in order to facilitate the removal of the guide tube 2 and the steel cage 4, the concrete 6 should be lower than the height of the foam sleeve 3, such as Figure 8 shown.

[0042] S4: After the strength of the concrete 6 to be backfilled meets the requirements, the second drill bit is lowered through the guide tube 2, and the inclined rock is drilled by the second drill bit until the inclined rock stratum is drilled through; S5: After the drilling of the guide tube 2 is completed, the steel cage 4 and the guide tube 2 are pulled out together, and the original first drill bit is used to continue the drilling construction. After the steel cage 4 is cleaned, it is used as a permanent force-bearing steel cage 4 of the pile foundation.

[0043] During the drilling process, the thinner the drill bit and the longer the drill rod, the easier it is to bend and deform, and the worse the stability of the drill bit at the end is. There is a phenomenon that the drill rod drives the drill bit to swing. If the strength difference of the rock formation is large, the drill bit is easy to deviate to the side with smaller strength during drilling, making it difficult to drill the inclined rock formation. In this embodiment, when the drill bit drills to a certain distance from the top of the inclined rock layer 1, the borehole has not yet deviated. This solution reduces the overall strength of the inclined rock by setting a guide tube 2 in the borehole and backfilling concrete 6 in the borehole, and drilling a small hole at the bottom of the concrete 6 by the second drill bit until the inclined rock formation is drilled through; the setting of concrete 6 ensures the stability of the guide tube 2 during the drilling process of the second drill bit, and the positioning setting of the guide tube 2 reduces the free length of the drill rod and the drill bit in the bottom soil layer, which can make the construction of the drill rod and the drill bit more stable. At this time, the displacement of the second drill bit at the inclined rock layer 1 is small, and it is easier to embed the entire section into the inclined rock formation. When the overall strength of the inclined rock has been reduced, a large-diameter first drill bit is used to drill downward on the horizontal section of the concrete 6. At this time, the first drill bit is less likely to deflect when encountering the residual structure of the inclined rock stratum, which is more conducive to embedding the entire section of the first drill bit into the inclined rock layer 1, reducing the error in the verticality of the pile hole, so that the inclination of the pile body of the pile foundation can be controlled within the allowable error range, thereby improving the quality of the pile and the bearing capacity of the pile.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bridge pile foundation construction method suitable for inclined rock strata, characterized in that: The following steps are involved: S1: using a first drill bit to drill into the inclined rock layer (1) at the pile position, so that the inclined rock layer (1) is exposed to form a pile bottom section; S2: lowering a plurality of guide tubes (2) into the borehole so that each of the guide tubes (2) contacts the cross section of the pile bottom, and temporarily fixing all of the guide tubes (2), wherein the bottom of the guide tubes (2) is wrapped with a foam casing (3), and the inclined rock layer corresponds to the position of the guide tubes (2); S3: pouring concrete (6) into the drilled hole, wherein the concrete (6) is used to fix all the guide pipes (2), and the concrete (6) is not higher than the top of the foam sleeve (3); S4: After the strength of the concrete (6) meets the requirements, a second drill bit is lowered through the guide tube (2), and the inclined rock is drilled using the second drill bit until the inclined rock stratum is penetrated; S5: pulling out the guide tube (2) and continuing drilling construction using the first drill bit.

2. The bridge pile foundation construction method according to claim 1, characterized in that: In step S2, the guide tube (2) is fixedly connected to the steel cage (4) via at least one layer of steel mesh (5); the steel cage (4) is used to support the drill hole; the lowered position of the steel cage (4) in the drill hole is not lower than the top position of the foam sleeve (3); and the steel mesh (5) is used to position and penetrate the guide tube (2).

3. The bridge pile foundation construction method according to claim 2, characterized in that: In step S5, the steel cage (4) and the guide tube (2) are pulled out together; After the hole is formed, the steel cage (4) is used as a permanent stress-bearing steel cage (4) of the pile foundation.

4. The bridge pile foundation construction method according to claim 2, characterized in that: A layer of the steel mesh (5) is arranged every 0.7 m to 1.2 m along the length direction of the steel cage (4), and each layer of the steel mesh (5) is fixedly connected to the guide tube (2).

5. The bridge pile foundation construction method according to claim 1, characterized in that: The top surface of the guide tube (2) is flush with the ground.

6. The bridge pile foundation construction method according to claim 1, characterized in that: The concrete is above the top of the inclined rock face.

7. The bridge pile foundation construction method according to claim 1, characterized in that: The inner diameter of the guide tube (2) is 8 cm-15 cm.

8. The bridge pile foundation construction method according to any one of claims 1 to 7, characterized in that: The length of the foam sleeve (3) is greater than the slope height of the inclined rock, and the foam sleeve (3) is 2m-3m long.

9. The bridge pile foundation construction method according to any one of claims 1 to 7, characterized in that: The first drill bit is an impact drill or a rotary drill, and the second drill bit is an auger.

10. The bridge pile foundation construction method according to any one of claims 1 to 7, characterized in that: Step S1 is replaced by using the first drill bit to drill at the pile position to a position above the top of the inclined rock layer (1), and stopping drilling, thereby forming a pile bottom section.

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