Grouting reinforcement method for weak intercalated layer in pile end stress concentration area

Abstract

The invention provides a grouting reinforcement method for a weak intercalated layer in a pile tip stress concentration area, which comprises the following steps: firstly, drilling exploration treatment is carried out on the weak intercalated layer below a pile foundation to determine geological parameters of the weak intercalated layer, and the weak intercalated layer comprises a pile tip soil area corresponding to a pile tip and a pile periphery soil area surrounding the outer side of the pile tip soil area; secondly, permeation filling grouting treatment is conducted on the soil layer defects of the soil area around the pile; thirdly, splitting grouting treatment is conducted on the remaining soil layer defects obtained after permeation filling grouting treatment; and finally, a cone area enveloped by the 45-degree divergence angle below the pile end is subjected to compaction grouting treatment, and the height of the cone area is the same as the thickness of the weak intercalated layer. According to the grouting reinforcement method for the weak intercalated layer in the pile end stress concentration area, the weak intercalated layer at the bottom of the pile foundation is subjected to composite grouting from outside to inside by adopting different grouting machines according to different stages, and finally the pile end reinforcement effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of foundation grouting reinforcement, and in particular to a grouting reinforcement method for a soft interlayer in a pile end stress concentration zone. Background Art

[0002] The pile foundation of a building transfers the upper structure load to a deeper and harder stratum through the soil layer at the pile end, thereby ensuring the safety of the building. If the pile end does not reach the hard soil layer or there is too much sediment during construction, a weak interlayer will exist at the bottom of the pile. When the bearing capacity of the soil layer at the pile end is insufficient and the compression modulus is low, under the action of the upper load, the weak interlayer will experience a large compression deformation or the pile body will "pierce" the weak interlayer, causing the building to settle. In severe cases, it will cause deformation, tilting, or even collapse of the components.

[0003] At present, the commonly used treatment measures are to use pile replacement or grouting reinforcement. However, pile replacement is affected by the limited use space of existing buildings, and the cost of pile replacement is high and the cycle is long. Grouting reinforcement mainly uses grouting at the pile end to make the loose particles produce a cementing effect, improve the strength and stiffness of the weak interlayer at the pile end, and achieve the effect of reinforcement and anti-sinking. However, at this stage, the grouting reinforcement of soft strata of pile foundation still has the following difficulties: First, under the vertical load of the pile body, the compressive stress is concentrated in the core area below the pile end, and the soil in the core area is denser than the surrounding soil. During grouting, the slurry flows preferentially to the surrounding looser soil, making it difficult to effectively reinforce the core area of ​​the pile end; secondly, if there are cracks, holes, caves and other loose areas in the soft strata at the pile end, the slurry will flow along the loose area during grouting, far exceeding the force range of the pile foundation, resulting in a huge waste of slurry.

[0004] Therefore, a method for grouting reinforcement of the weak interlayer in the stress concentration area at the pile end is urgently needed to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for reinforcing a weak interlayer in a pile end stress concentration zone by grouting, so as to solve the technical problem of poor reinforcement quality of the existing method for reinforcing a weak interlayer in a pile end stress concentration zone by grouting.

[0006] In order to solve the above technical problems, the present invention first provides a method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end by grouting, comprising: S10, drilling and surveying the soft interlayer under the pile foundation to determine geological parameters of the soft interlayer, wherein the soft interlayer includes a pile end soil area corresponding to the pile end and a pile surrounding soil area surrounding the pile end soil area; S20, performing infiltration filling grouting treatment on soil defects in the soil area around the pile; S30, performing splitting grouting treatment on the remaining soil layer defects after the infiltration filling grouting treatment; S40, compaction grouting treatment is carried out on the conical area enclosed by the 45° diffusion angle below the pile end. The height of the conical area is the same as the thickness of the weak interlayer.

[0007] Preferably, in step S10, at least one of a comprehensive core drilling method, an underwater television observation method and a magnetic well method is used to perform drilling exploration on the weak interlayer below the pile foundation.

[0008] Preferably, before performing step S20, the method further includes: drilling a plurality of grouting reinforcement groups in sequence at the edge of the pile end soil area in a direction away from the ground, each grouting reinforcement group comprising a plurality of grouting holes, and the plurality of grouting holes in each grouting reinforcement group are combined into a circular area.

[0009] Preferably, in step S20, a first grouting material is injected through a plurality of grouting holes using a drilling-injection integrated grouting device; the water-cement ratio of the first grouting material is 1.0-1.5, and the initial setting time is 10-60 min.

[0010] Preferably, the length of each grouting section injected into the grouting hole does not exceed 30 cm, and the grouting pressure is 0.2~1.0 MPa.

[0011] Preferably, in step S30, the second grouting material is injected through a plurality of grouting holes using a drilling and injection integrated grouting device; the water-cement ratio of the second grouting material is 0.6-1.0, and the initial setting time is 60s-30min.

[0012] Preferably, the length of each grouting section injected into the grouting hole does not exceed 20 cm, and the grouting pressure is 0.5~2.0 MPa.

[0013] Preferably, in step S40, the third grouting material is injected through a plurality of grouting holes using a drilling and injection integrated grouting device; the water-cement ratio of the third grouting material is 0.4-0.6, and the initial setting time is 30s-10min.

[0014] Preferably, the length of each grouting section injected into the grouting hole does not exceed 10 cm, and the grouting pressure is 2.0~3.0 MPa.

[0015] Preferably, before performing step S10, the method further includes: performing grouting reinforcement treatment on the soil layers on both sides of the pile foundation.

[0016] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a method for grouting reinforcement of a weak interlayer in a stress concentration area at a pile end, comprising: firstly, drilling and surveying the weak interlayer below the pile foundation to determine the geological parameters of the weak interlayer, the weak interlayer comprising a pile end soil area corresponding to the pile end and a pile surrounding soil area surrounding the outside of the pile end soil area; secondly, performing infiltration filling grouting treatment on soil layer defects in the pile surrounding soil area; thirdly, performing splitting grouting treatment on the remaining soil layer defects after the infiltration filling grouting treatment; finally, performing compaction grouting treatment on a conical area enclosed by a 45° diffusion angle below the pile end, the height of the conical area being the same as the thickness of the weak interlayer. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end provided by the present invention performs composite grouting from outside to inside on the weak interlayer at the bottom of the pile foundation by using different grouting machines at different stages, wherein, in the first stage, the soil defects in the soil area around the pile are first treated with infiltration filling grouting to block the slurry channel; in the second stage, splitting grouting is performed on the remaining soil defects after the infiltration filling grouting treatment, and the spatial skeleton effect of the soil in the soil area around the pile is enhanced by forming splitting slurry veins, thereby forming a slurry-stopping curtain for the core area of ​​the pile end; in the third stage, the core area of ​​the pile end is compacted and grouting is performed to form a continuous vertical columnar stone body, and finally the pile end reinforcement effect is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of a method for reinforcing a weak interlayer in a pile end stress concentration zone provided by an embodiment of the present invention by grouting; Figure 2 A schematic diagram of the structure of a weak interlayer at a pile end in a grouting reinforcement method for a weak interlayer at a stress concentration zone at a pile end provided by an embodiment of the present invention; Figure 3 A schematic diagram of reinforcement during penetration filling grouting treatment in the grouting reinforcement method for the weak interlayer in the stress concentration zone of the pile end provided by an embodiment of the present invention; Figure 4 A schematic diagram of reinforcement during split grouting treatment in the grouting reinforcement method for the weak interlayer in the stress concentration zone of the pile end provided by an embodiment of the present invention; Figure 5 A schematic diagram of reinforcement during compaction grouting treatment in the grouting reinforcement method for the weak interlayer in the stress concentration zone of the pile end provided by an embodiment of the present invention; Figure 6 A photograph of the on-site grouting reinforcement of the weak interlayer in the stress concentration zone of the pile end provided in Example 1 of the present invention; Figure 7a The static load Qs curve before grouting of the weak interlayer grouting reinforcement method in the stress concentration area of ​​the pile end provided in Example 1 of the present invention; Figure 7bThe static load Qs curve after grouting of the weak interlayer grouting reinforcement method in the stress concentration area of ​​the pile end provided in Example 1 of the present invention; Figure 8 This is the settlement curve at measuring point B of the grouting reinforcement method for the weak interlayer in the stress concentration area of ​​the pile end provided in Example 1 of the present invention.

[0018] In the figure: 10 - soil layer beside the pile; 20 - weak interlayer; 201 - soil area at the pile end; 202 - soil area around the pile 202; 30 - hard stratum; 41 - first grouting material; 42 - second grouting material; 43 - continuous vertical columnar stone body; 50 - grouting hole. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The purpose of the present invention is to provide a method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end by grouting in view of the defects of the prior art. The method has the advantages of good grouting targeting, reliable reinforcement of the force range of the pile foundation, low cost, short construction period, etc. The method uses different grouting machines to perform composite grouting from the outside to the inside on the weak interlayer at the bottom of the pile at different stages, greatly improving the reinforcement quality of the soil at the bottom of the pile foundation and achieving the effect of rapid reinforcement and anti-sinking.

[0021] In order to achieve the above technical purpose, the technical solution adopted by the present invention is: See also Figure 1 , Figure 1 A flow chart of a grouting reinforcement method for a weak interlayer 20 in a pile end stress concentration zone provided by an embodiment of the present invention; wherein the grouting reinforcement method specifically includes the following steps: S10, drilling and surveying the weak interlayer 20 below the pile foundation 11 to determine the geological parameters of the weak interlayer 20, the weak interlayer 20 includes a pile end soil area 201 corresponding to the pile end and a pile surrounding soil area 202 surrounding the pile end soil area 201.

[0022] Specifically, step S10 also includes: The weak interlayer 20 below the pile foundation 11 is drilled and explored by at least one of a comprehensive core drilling method, an underwater television observation method, and a magnetic well method, so as to detect the length of the pile foundation 11, the soil distribution in the area where the weak interlayer 20 is located, and the groundwater level, so as to obtain the soil parameters in the area where the weak interlayer 20 is located, and the soil parameters include the soil layer defects 21 (non-compacted areas such as holes or cracks) in the soil area 202 around the pile.

[0023] See also Figure 2 , Figure 2 A schematic diagram of the structure of the weak interlayer 20 at the pile end in the grouting reinforcement method of the weak interlayer 20 in the stress concentration area of ​​the pile end provided by the embodiment of the present invention; wherein, under the action of the pile body load, if the pile end of the pile foundation 11 does not reach the hard soil layer or there is too thick sediment during construction, a weak interlayer 20 will be formed at the bottom of the pile. Within the thickness range of the weak interlayer 20, the cone-shaped stress-bearing area formed by diffusion at a diffusion angle of 45º~60º along the bottom of the pile end is the pile end soil area 201 (also called the stress concentration area); the stress in the pile end soil area 201 is greater than the stress in the pile surrounding soil area 202 surrounding the outside of the pile end soil area 201.

[0024] Preferably, before performing step S10, the method further includes: performing grouting reinforcement treatment on the pile side soil layer 10 on both sides of the pile foundation 11; this can increase the friction resistance of the pile side soil layer 10 and achieve a better reinforcement effect.

[0025] S20, performing infiltration filling grouting treatment on the soil layer defects 21 in the soil area 202 around the pile.

[0026] Specifically, step S20 includes: First, a plurality of grouting reinforcement groups are drilled in sequence at the edge of the pile end soil area 201 in a direction away from the ground using a drilling and grouting device. Each grouting reinforcement group includes a plurality of grouting holes 50. The plurality of grouting holes 50 in each grouting reinforcement group are combined into a circular area.

[0027] Afterwards, a drilling and grouting device is used to inject a first grouting material 41 with strong permeability through a plurality of grouting holes 50 to perform a permeation filling grouting treatment on the soil layer defects 21 in the soil area 202 around the pile. Figure 3 As shown, Figure 3 A schematic diagram of reinforcement during penetration filling grouting treatment in the grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end provided in an embodiment of the present invention; wherein the water-cement ratio of the first grouting material 41 is 1.0-1.5, and the initial setting time is 10-60 minutes.

[0028] Furthermore, during the infiltration filling grouting treatment process: along the direction from the bottom of the pile foundation 11 to the hard stratum 30, progressive grouting is performed in layers and sections through the corresponding multiple grouting holes 50 in the grouting reinforcement groups of different depths. The length of each grouting section does not exceed 30 cm, and the grouting pressure is 0.2~1.0 MPa.

[0029] Furthermore, the diffusion distance L of the first grouting material 41 injected through the grouting hole 50 is greater than or equal to D+2H, where D is the diameter of the pile foundation 11 and H is the thickness of the weak interlayer 20 .

[0030] Furthermore, the calculation method of the grouting pressure head height h of the drilling and grouting equipment during the infiltration filling grouting treatment process is shown in formula (1) and formula (2): (1); (2); Where Q is the slurry flow rate (cm 3 / s); K is the formation permeability (cm / s); β is the ratio of slurry viscosity to water viscosity, μ w is the dynamic viscosity coefficient of water (mPa·s); μ g is the dynamic viscosity coefficient of the slurry (mPa·s); r0 is the spherical diffusion radius; r1 is the slurry diffusion radius (cm).

[0031] Furthermore, the time t required for the first grouting material 41 to diffuse from the grouting source (the bottom of the grouting pipe of the drilling and grouting integrated grouting equipment) to the spherical surface with a radius of R is calculated as shown in formula (3):

[0032] Where n is the soil porosity.

[0033] S30, performing splitting grouting treatment on the remaining soil layer defects 21 after the infiltration filling grouting treatment.

[0034] The second grouting material 42 with a shorter setting time is injected through a plurality of grouting holes 50 by using a drilling and injection integrated grouting device to perform splitting grouting treatment on the remaining soil layer defects 21 after the infiltration filling grouting treatment, such as Figure 4 As shown, Figure 4 A schematic diagram of reinforcement during splitting grouting treatment in the grouting reinforcement method for the weak interlayer 20 in the stress concentration zone of the pile end provided in an embodiment of the present invention; wherein the water-cement ratio of the second grouting material 42 is 0.6~1.0, and the initial setting time is 60s~30min.

[0035] In one embodiment, the water-cement ratio of the second grouting material 42 is smaller than that of the first grouting material 41 , and the initial setting time of the second grouting material 42 is smaller than that of the first grouting material 41 .

[0036] Specifically, during the splitting grouting treatment process: along the direction from the bottom of the pile foundation 11 to the hard stratum 30, progressive grouting is performed in layers and sections through the corresponding multiple grouting holes 50 in the grouting reinforcement groups of different depths. The length of each grouting section does not exceed 20 cm, and the grouting pressure is 0.5~2.0 MPa.

[0037] Specifically, the second stage grouting reinforcement process adopts the splitting grouting method, the purpose of which is to reinforce the loose soil in the outer pile surrounding soil area 202, form a network of slurry veins in the surrounding soil of the pile end core area, improve the spatial skeleton effect of the soil, increase the deformation modulus, reach or approach the requirements of the pile end core area, and form a grouting curtain in the pile end core area.

[0038] Furthermore, the grouting amount of the splitting grouting treatment in the second stage is controlled according to the grouting amount of a single grouting hole 50. The calculation method of the single hole grouting amount Q is shown in formula (4):

[0039] Among them, L is the length of each grouting section, R is the slurry diffusion radius, n is the porosity of the soil layer in the grouting section, and η is the slurry loss rate.

[0040] S40, compaction grouting treatment is performed on the conical area enclosed by the 45° diffusion angle below the pile end, and the height of the conical area is the same as the thickness of the weak interlayer 20.

[0041] Specifically, step S40 also includes: The third grouting material with high consistency and short setting time is injected through multiple grouting holes 50 by drilling and grouting equipment to perform compaction grouting treatment on the cone area (i.e. the core area of ​​the pile end) enclosed by a 45° diffusion angle below the pile end, and a continuous vertical columnar stone body 43 is formed, thereby finally achieving the effect of strengthening the pile end. Figure 5 As shown, Figure 5 A schematic diagram of reinforcement during compaction grouting treatment in the grouting reinforcement method for the weak interlayer 20 in the stress concentration zone of the pile end provided in an embodiment of the present invention; wherein the water-cement ratio of the third grouting material is 0.4~0.6, and the initial setting time is 30s~10min.

[0042] In one embodiment, the water-cement ratio of the third grouting material is smaller than that of the second grouting material 42 , and the initial setting time of the third grouting material is smaller than that of the second grouting material 42 .

[0043] Specifically, during the compaction grouting treatment process: along the direction from the bottom of the pile foundation 11 to the hard stratum 30, progressive grouting is performed in layers and sections through the corresponding multiple grouting holes 50 in the grouting reinforcement groups of different depths. The length of each grouting section does not exceed 10 cm, and the grouting pressure is 2.0~3.0 MPa.

[0044] Furthermore, when there are multiple interlayers of weak interlayers 20 in the conical area enclosed by the 45° diffusion angle below the pile end, the conical area should cover all the weak interlayers 20, and the bottom of the conical area is a dense hard stratum 30.

[0045] Furthermore, the calculation method of the grouting volume V2 of the compaction grouting treatment by the drilling and grouting integrated grouting equipment is shown in formula (5): V2=π×r22 / 4×H(5);wherein, r2 is the slurry compaction diffusion radius, and H is the thickness of the weak interlayer 20.

[0046] The present invention will now be further described with reference to specific embodiments.

[0047] Embodiment 1: See also Figure 6 , Figure 6 The following is a photograph of the on-site grouting reinforcement of the weak interlayer 20 in the pile end stress concentration zone provided in Example 1 of the present invention; wherein the basic parameters provided in Example 1 of the present invention are as follows: the pile diameter is 900 mm, the pile length is 30.5 m, the radius of the grouting hole 50 is 2.5 cm, the thickness H of the weak interlayer 20 is 3 m, and the permeability coefficient is 5×10- 2 cm / s, porosity ratio 0.9.

[0048] Specifically, the steps of the grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end provided in Example 1 of the present invention are as follows: Step (1), before grouting reinforcement, the length of the pile foundation 11, the distribution of the surrounding soil layers and the groundwater level are detected by using a comprehensive core drilling method, an underwater television observation method, a magnetic well method, etc.

[0049] Step (2), the first stage of grouting adopts the progressive segmented grouting process to carry out grouting on the pile side and pile end, with a water-cement ratio of 1.2, an initial setting time of 60 min, a grouting pressure of 1.0 MPa, a grouting volume of 50 L / min, a diffusion radius of 1.0 m, a slurry flow rate Q of 833.33 / 2, a formation permeability coefficient K of 0.05, and a slurry dynamic viscosity coefficient μ g Take 0.9mPa·s, the dynamic viscosity coefficient of water μ w is 1 mPa·s, the spherical diffusion radius r0 is 2.5 cm; the slurry diffusion radius is 100 cm, and the soil porosity n is 0.9; among them, the grouting pressure head height h1 of the drilling and grouting equipment during the infiltration filling grouting treatment process is substituted into formula (1) and formula (2) to obtain: = =251.33cm;

[0050] =0.90;

[0051] At this time, the time t required for the first slurry to diffuse from the grouting source (bottom of the grouting pipe) to the spherical surface with a radius of 1m is substituted into formula (3) to obtain: =

[0052] Step (3), the second stage adopts the split grouting method, the purpose is to reinforce the loose soil at the periphery, form a network of slurry veins in the core area of ​​the non-pile end, improve the spatial skeleton effect of the soil, increase the deformation modulus, and form a grouting curtain. The grouting water-cement ratio is 0.8, the initial setting time is 30min, and the grouting pressure is 0.8Mpa. The grouting volume in the second stage is controlled according to the single-hole grouting volume. The length of each grouting section L is 3m, the slurry diffusion radius R is 1m, the porosity n of the grouting section soil layer is 47.4% (the porosity is calculated as 0.9), η is the slurry loss rate η is 1.25, and the single-hole grouting volume is calculated according to formula (4) as follows: *3*12*47.4%*1.25=5.58m 2 ; Step (4), the third stage adopts compaction grouting, the purpose is to form a columnar reinforcement body at the pile end, squeeze out the surrounding soil to achieve replacement effect, and maintain the balance of grouting energy and compaction. The water-cement ratio of grouting in this stage is 0.5, the initial setting time is about 50min, the grouting pressure is 2.50Mpa, and the slurry compaction diffusion radius r2 is 0.5m; the calculation method of the grouting volume V2 of the compaction grouting treatment by the drilling and grouting integrated grouting equipment is shown in formula (5): V2=π×r2 2 *H=π*0.5 2 *3=2.36m 3 (5).

[0053] See also Figure 7a as well as Figure 7b , Figure 7a The static load Qs curve before grouting of the weak interlayer 20 in the stress concentration area of ​​the pile end provided in Example 1 of the present invention; Figure 7b The static load Qs curve of the grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end provided in Example 1 of the present invention after grouting; wherein the static load Qs curve is a relationship curve between the load (Q) and the settlement (s) obtained by static load test before and after grouting treatment of the soil or structure.

[0054] Specifically, according to Figure 7a as well as Figure 7b From the static load test comparison, it can be seen that the bearing capacity of the pile foundation 11 after grouting is increased by more than 2 times, and the bearing capacity of the pile foundation 11 after grouting meets the requirements for building use.

[0055] See also Figure 8 , Figure 8 The settlement curve of the weak interlayer 20 in the pile end stress concentration area grouting reinforcement method at the measuring point B provided in Example 1 of the present invention; wherein, Figure 8From the monitoring curve of building settlement before and after grouting, it can be seen that the building settlement tends to be stable obviously after grouting, and the grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end provided by the present invention is used to perform grouting reinforcement in the stress concentration area of ​​the pile end to achieve good results.

[0056] Compared with the prior art, the present invention has the following beneficial effects: (1) If there are cracks, holes, karst caves and other loose areas in the soft strata at the pile end, the slurry will flow along the loose areas during grouting, far exceeding the stress range of the pile foundation 11, resulting in a huge waste of slurry. The grouting method proposed in the present invention adopts permeation grouting in the first stage. During the flow of slurry, the slurry will first fill various holes in the interlayer. By controlling the setting time, the problem of slurry waste is effectively solved. At the same time, it is ensured that there are no cracks, holes, karst caves and other loose areas in the stress transfer area, providing a guarantee for subsequent grouting reinforcement.

[0057] (2) Under the vertical load of the pile body, the compressive stress is concentrated in the core area below the pile end. The soil in the core area is denser than the surrounding soil. During grouting, the slurry preferentially flows to the looser soil around the pile, which makes it difficult to effectively reinforce the core area of ​​the pile end. The grouting method proposed in the present invention adopts splitting grouting in the second stage. During the grouting process, the slurry preferentially splits and reinforces the loose soil around the pile, forming slurry veins on the periphery of the conical core area, improving the spatial skeleton effect of the area, and forming a slurry-stopping curtain, which provides a guarantee for the grouting reinforcement in the third stage.

[0058] (3) Based on the grouting in the first two stages, the third stage used a thicker slurry to compact the soil in the conical core area at the bottom of pile foundation 11, effectively avoiding the risks of leakage, slurry channeling, and slurry leakage, achieving "localized, directional, and quantitative" targeted treatment, greatly saving grouting materials and construction time, reducing project costs, and improving the quality of grouting reinforcement.

[0059] In summary, different from the prior art, the present invention provides a grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end, comprising: first, drilling and surveying the weak interlayer 20 below the pile foundation 11 to determine the geological parameters of the weak interlayer 20, the weak interlayer 20 including a pile end soil area 201 corresponding to the pile end and a pile surrounding soil area 202 surrounding the outside of the pile end soil area 201; secondly, performing infiltration filling grouting treatment on the soil layer defects 21 in the pile surrounding soil area 202; thirdly, performing splitting grouting treatment on the remaining soil layer defects 21 after the infiltration filling grouting treatment; finally, performing compaction grouting treatment on the conical area enclosed by a 45° diffusion angle below the pile end, the height of the conical area being the same as the thickness of the weak interlayer 20. The grouting reinforcement method for the weak interlayer 20 in the stress concentration area of ​​the pile end provided by the present invention performs composite grouting from the outside to the inside on the weak interlayer 20 at the bottom of the pile foundation 11 using different grouting machines at different stages, wherein, in the first stage, the soil layer defects 21 in the soil area 202 around the pile are first subjected to infiltration filling grouting treatment to block the slurry channel; in the second stage, splitting grouting is performed on the remaining soil layer defects 21 after the infiltration filling grouting treatment, and the spatial skeleton effect of the soil in the soil area 202 around the pile is enhanced by forming splitting slurry veins, thereby forming a slurry-stopping curtain for the core area of ​​the pile end; in the third stage, the core area of ​​the pile end is subjected to compaction grouting, and a continuous vertical columnar stone body 43 is formed, finally achieving the pile end reinforcement effect.

[0060] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0061] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for reinforcing the weak interlayer in the stress concentration area of ​​a pile end by grouting, characterized in that: include: S10, drilling and surveying the soft interlayer below the pile foundation to determine geological parameters of the soft interlayer, wherein the soft interlayer includes a pile end soil area corresponding to the pile end and a pile surrounding soil area surrounding the pile end soil area; S20, performing a permeable filling grouting treatment on the soil defects in the soil area around the pile; S30, performing splitting grouting treatment on the remaining soil layer defects after the permeable filling grouting treatment; S40, performing compaction grouting treatment on a conical area enclosed by a 45° diffusion angle below the pile end, wherein the height of the conical area is the same as the thickness of the weak interlayer.

2. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 1 is characterized in that: In the step S10, at least one method selected from the group consisting of a comprehensive core drilling method, an underwater television observation method, and a magnetic well method is used to perform drilling exploration on the weak interlayer below the pile foundation.

3. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 1 is characterized in that: Before performing the S20 step, it also includes: drilling a plurality of grouting reinforcement groups in sequence at the edge of the pile end soil area in a direction away from the ground, each of the grouting reinforcement groups includes a plurality of grouting holes, and the plurality of grouting holes in each of the grouting reinforcement groups are combined into a circular area.

4. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 3 is characterized in that: In the step S20, a first grouting material is injected through the plurality of grouting holes using a drilling and injection integrated grouting device; the water-cement ratio of the first grouting material is 1.0-1.5, and the initial setting time is 10-60 minutes.

5. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 4 is characterized in that: The length of each grouting section injected into the grouting hole does not exceed 30 cm, and the grouting pressure is 0.2~1.0Mpa.

6. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 3 is characterized in that: In the step S30, the drilling-injection integrated grouting equipment is used to inject the second grouting material through the plurality of grouting holes; the water-cement ratio of the second grouting material is 0.6-1.0, and the initial setting time is 60s-30min.

7. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 6 is characterized in that: The length of each section of grouting injected into the grouting hole does not exceed 20 cm, and the grouting pressure is 0.5~2.0 MPa.

8. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 3 is characterized in that: In the step S40, the drilling-injection integrated grouting equipment is used to inject a third grouting material through the plurality of grouting holes; the water-cement ratio of the third grouting material is 0.4-0.6, and the initial setting time is 30s-10min.

9. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end according to claim 8, characterized in that: The length of each grouting section injected into the grouting hole does not exceed 10 cm, and the grouting pressure is 2.0~3.0 MPa.

10. The method for reinforcing the weak interlayer in the stress concentration area of ​​the pile end by grouting according to any one of claims 1 to 9, characterized in that: Before performing the step S10, the method further includes: performing grouting reinforcement treatment on the soil layers on both sides of the pile foundation.

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