A karst area foundation design method and system based on comprehensive geophysical exploration

Abstract

The present invention belongs to the technical field of karst space detection, and specifically discloses a karst area foundation design method and system based on comprehensive geophysical exploration, wherein the method includes using a comprehensive geophysical exploration method combining a high-density resistivity method, a micro-motion detection method and an elastic wave CT method to detect the karst area to obtain the position distribution law of the karst development area; after the foundation pit is excavated, a cushion layer is laid under the base to adjust the uneven settlement; a pile foundation is used at the position where the single column load is the largest, and the building foundation adopts a combination of a pile foundation and a raft foundation. The use of a comprehensive geophysical exploration method can not only quickly delineate the development area of ​​the karst cave, but also accurately locate the size and scale of the karst cave, which can provide valuable reference for the foundation design and foundation treatment in the karst area. Based on the comprehensive exploration results, targeted karst foundation treatment can not only effectively solve karst engineering problems, but also save a lot of construction time and cost.

Description

Technical Field

[0001] The invention belongs to the technical field of karst space detection, and in particular relates to a karst area foundation design method and system based on comprehensive geophysical exploration. Background Art

[0002] Karst is a special adverse geological effect, and the karst area in my country is widely distributed. The traditional method of dealing with caves is usually to fill the caves with cement slurry, concrete or other waste residues, or to use pile foundations to pass through the caves to reinforce the foundation. However, when the caves to be treated are deep and large in scope, if the material filling method is continued, serious material consumption and uneconomical phenomena will occur, so this method is no longer applicable. When pile foundations are traditionally used, leakage, necking and collapse of the pile hole are prone to occur during the forming process, and when pouring concrete, it is easy to cause over-pouring of concrete, high filling coefficient, and lack of stable piers at the bottom of the pile foundation.

[0003] In addition, the karst cavity has a complex orientation. When the pile-sheet structure is used to cross the cavity, it is difficult for the pile foundation to avoid crossing the cavity. When the pile foundation is located in the cavity and the cavity is large, the exposed pile foundation of the existing pile-sheet structure is easily hit by the rock blocks collapsed from the top of the cavity during the later operation process, causing damage. These damages seriously affect the normal operation of the railway and greatly increase the operation and maintenance expenses of the roadbed.

[0004] In summary, when karst detection is not accurate enough, whether it is excessive use of cement grout, concrete or other waste residue to fill the cave, or the use of pile foundations to pass through the cave to reinforce the foundation, it is impossible to achieve accurate and resource-saving foundation support. The traditional rough method is not only time-consuming, labor-intensive and economically costly, but also the overall support effect is unstable, which is not conducive to the construction of tall buildings and has high safety risks. Summary of the invention

[0005] The purpose of the present invention is to provide a karst area foundation design method and system based on comprehensive geophysical exploration, which can solve the technical problem of how to specifically design the foundation to improve stability and save costs when the karst development and underground cave structure are very complex.

[0006] The present invention provides a karst area foundation design method based on comprehensive geophysical exploration, comprising the following steps:

[0007] S1, the karst area is detected by using a comprehensive geophysical method combining high-density resistivity method, micro-seismic detection method and elastic wave CT method to obtain the location distribution law of the karst development area;

[0008] S2, after the excavation of the foundation pit, a cushion layer is laid under the base to adjust the uneven settlement;

[0009] S3, pile foundation is used at the location where the single column load is the largest, and the building foundation adopts a combination of pile foundation and raft foundation.

[0010] Preferably, the S1 specifically includes:

[0011] S101, using high-density resistivity method to conduct overall detection of the target area to delineate the karst development area;

[0012] S102, local detection of karst development areas is carried out by micro-motion detection method to obtain the karst development range, preliminary scale and undulating form of bedrock surface, and obtain local karst development areas;

[0013] S103, elastic wave CT method is used to finally locate the local karst development area, and the precise position, scale and burial depth of the karst are obtained.

[0014] Preferably, the S3 specifically includes:

[0015] The basement and 4-story buildings use slab raft foundations, and the 7-story and 9-story buildings use pile foundations;

[0016] The raft foundation uses the silty clay layer, silty sand layer, and residual silty clay layer at the basement floor elevation as the bearing layer, and the pile foundation uses slightly weathered marble as the basic bearing layer;

[0017] Anti-floating measures are combined with foundation forms to adopt anti-floating piles or anti-pullout anchors.

[0018] Preferably, S3 specifically includes: designing a raft foundation in the pure basement and the 4-story building; the raft foundation adopts HRB400 grade φ25 steel bars with double-layer bidirectional reinforcement to meet the bearing capacity requirements.

[0019] Preferably, the thickness of the karst overlying soil layer at the raft foundation is not less than the thickness of the compression layer of the raft foundation foundation.

[0020] Preferably, the S3 specifically includes:

[0021] When there is a cave within a range of 3 times the pile diameter less than 5m directly below the pile end, the pile foundation penetrates the cave to reach a complete bearing layer;

[0022] When the buried depth of soil cave or karst cave is not more than 2.5m, the method of replacement filling or lowering steel casing is adopted. When replacing filling, the excavation slope ratio is not more than 1:1 or the actual stable slope; when lowering the steel casing, its height is not less than 1.5m above the top elevation of the karst cave;

[0023] When the depth of soil cave or karst cave is greater than 2.5m but less than 6m, backfill with stone flakes and clay and use a small-stroke punching machine to punch the hole.

[0024] When the buried depth of soil cave or karst cave is greater than 6m, cement slurry is poured or filled with C20 concrete for treatment; after the strength of cement slurry or concrete reaches 50% of the design strength, secondary rotary drilling is carried out and the skip drilling method is used for construction.

[0025] Preferably, the S3 specifically includes: when there is a karst cave within a range of 3 times the pile diameter less than 5m below the pile end side;

[0026] If the pile foundation under the ground-standing shear wall or column of the 7-story and 9-story building is filled with high-pressure grouting, or the pile end is extended below the bottom of the cave;

[0027] If the pile foundation under the podium building and pure basement columns has a top slab thickness greater than 5m, the cave will not be treated.

[0028] Preferably, S3 specifically includes: when the bearing layer test at the pile end after pile formation does not meet the requirements, a "high-pressure grouting to replace the cave filling" method is used for treatment, as follows:

[0029] First, the filling material in the karst cave under the pile end is fully cleaned by high-pressure flushing, so that clay and fine sand can be flushed out of the drill hole to the ground, and the remaining medium and coarse sand and gravel are used as aggregates for the grouting body;

[0030] Then cement slurry is injected into the cavity under high pressure to form a reinforcement.

[0031] Preferably, the S3 specifically includes:

[0032] When there is a cave within 5m below the raft foundation, it should be replaced or filled with C35 concrete;

[0033] When the depth of the cave under the raft foundation exceeds 5m, if the size of the cave is less than a certain threshold, additional reinforcement steel bars shall be added to the raft foundation within the plane distribution range of the cave;

[0034] If the size of the cave is larger than a certain threshold, reinforced concrete beams, slabs, arches and other structures can be used for spanning. When using spanning beams, ensure that the length of the beam end support on the bearing layer is not less than 1.5 times the height of the beam.

[0035] The present invention also provides a karst area foundation design system based on comprehensive geophysical exploration, and the system is used to implement a karst area foundation design method based on comprehensive geophysical exploration, which specifically includes:

[0036] The comprehensive geophysical exploration module is used to detect the karst area using a comprehensive geophysical exploration method that combines high-density resistivity method, micro-seismic detection method and elastic wave CT method to obtain the location distribution law of the karst development area;

[0037] The foundation pit excavation module is used to adjust the uneven settlement by laying a cushion layer under the base after the foundation pit is excavated;

[0038] The pile foundation module is used to adopt pile foundation at the location where the single column load is the largest. The building foundation adopts a combination of pile foundation and raft foundation.

[0039] Compared with the prior art, a karst area foundation design method and system based on comprehensive geophysical exploration according to the present invention includes: using a comprehensive geophysical exploration method combining high-density resistivity method, micro-motion detection method and elastic wave CT method to detect the karst area to obtain the position distribution law of the karst development area; after the foundation pit is excavated, a cushion layer is laid under the base to adjust the uneven settlement; pile foundations are used at the location where the single column load is the largest, and the building foundation adopts a combination of pile foundations and raft foundations. The comprehensive geophysical exploration method combining high-density resistivity method, micro-motion detection method and elastic wave CT method can not only quickly delineate the development area of ​​the karst cave, but also accurately locate the size and scale of the karst cave, which can provide valuable reference for the foundation design and foundation treatment in the karst area. Based on the comprehensive exploration results, targeted karst foundation treatment can not only effectively solve karst engineering problems, but also save a lot of construction time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flow chart of a karst space detection method based on comprehensive geophysical exploration provided by the present invention;

[0041] Figure 2 The invention provides a basic plane layout of a karst space detection method based on comprehensive geophysical exploration. DETAILED DESCRIPTION

[0042] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0043] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0044] like Figure 1 to Figure 2 As shown, a karst area foundation design method based on comprehensive geophysical exploration according to a preferred embodiment of the present invention comprises: S1, using a comprehensive geophysical exploration method combining a high-density resistivity method, a micro-motion detection method and an elastic wave CT method to detect the karst area to obtain the position distribution law of the karst development area;

[0045] S2, after the excavation of the foundation pit, a cushion layer is laid under the base to adjust the uneven settlement;

[0046] S3, pile foundation is used at the location where the single column load is the largest, and the building foundation adopts a combination of pile foundation and raft foundation.

[0047] Based on the comprehensive exploration results, targeted karst foundation treatment can not only effectively solve karst engineering problems, but also save a lot of construction time and costs.

[0048] This plan is aimed at the complex geological conditions of the site, the large fluctuations in the depth of the rock surface, the strong development of karst, and the geological survey report cannot accurately reflect the spatial morphology and distribution of the cave. After the excavation of the foundation pit, the slightly weathered marble is shallowly buried, and the rock layer is hard and thick and difficult to penetrate, so it is not suitable to use prestressed pipe piles. Although the punching (drilling) bored piles have strong penetration ability and can make the pile end reach the design elevation of the bearing layer more smoothly, their construction speed is slow, and it is difficult to identify the rock properties of the bearing layer at the pile end, and the quality of the pile is difficult to control. Therefore, in view of the tight schedule and high environmental protection requirements of this project, it is not appropriate to use the punching (drilling) bored pile technology. Considering the advantages of rotary piles, such as fast construction speed, large bearing capacity of single piles, and ability to meet the design bearing capacity requirements, combined with the engineering geological conditions of this site and project requirements, rotary piles are preferred.

[0049] In a further solution, step S1 specifically includes:

[0050] S101, the high-density resistivity method is used to conduct overall detection of the target area to delineate the karst development area.

[0051] S102, local detection of the karst development area is carried out by the micro-motion detection method to obtain the karst development range, preliminary scale and undulation of the bedrock surface, and obtain the local karst development area; specifically, two micro-motion measurement lines are arranged in the delineated karst development area, each with a length of 32m, a point distance of 4m, a total of 18 measurement points, and a sampling interval of 1280μs, and the filtering method is bandpass filtering.

[0052] S103, elastic wave CT method is used to finally locate the local karst development area, and the precise position, scale and burial depth of the karst are obtained.

[0053] In a specific implementation scenario, according to the comprehensive survey results, the base elevation after the excavation of the site foundation pit is about 30.75m, and the main strata of the base are mainly exposed silty clay layer, silty sand layer, residual silty clay layer, and local silty clay layer containing angular gravels in the trough accumulation. The number of floors of the proposed project is 4 to 9, and the floor load per floor is 20kN / m 2 Considering the uniformly distributed load of the building and the bearing capacity of the underlying rock and soil layer, the load is shown in Table 1.

[0054] Table 1 Building load and rock and soil bearing capacity

[0055]

[0056] From the results in Table 1, it can be seen that the uniformly distributed load of the proposed building at the base elevation is less than the bearing capacity correction value of the rock and soil layer at its base. Therefore, the natural foundation can be used under the premise of considering the uniformly distributed load. Considering that the bearing capacity of each rock and soil layer is quite different, it is an uneven foundation, so it is necessary to adopt the measure of laying a cushion layer under the base to adjust the uneven settlement. In addition, the span of the structural beam at the local position of the site building is large, and the maximum single column load is 10000~15000kN. For the location with large single column load, pile foundation is adopted to meet the bearing capacity requirements.

[0057] In summary, according to the construction load characteristics of this project, the building foundation adopts a combination of pile foundation and raft foundation. The basement and 4-story building adopt plate raft foundation, and the 7-story and 9-story building adopt pile foundation. The raft foundation uses the silty clay layer, silty sand layer, and residual silty clay layer at the basement ground elevation as the bearing layer, and the pile foundation uses slightly weathered marble as the basic bearing layer. Anti-floating measures are combined with the foundation form to adopt anti-floating piles or anti-pullout anchor rods. The foundation plane layout is as follows: Figure 2 shown.

[0058] The preferred solution is to use pile foundations, and the bearing capacity of pile foundations is calculated according to the Code for Design of Building Foundations (DBJ 15-31-2016) and related specifications. Combined with the experience of similar sites, the characteristic value of the friction resistance of the pile side of each rock and soil layer is q sa and the characteristic value of soil bearing capacity at the pile end q pa Refer to Table 2. The natural moisture uniaxial compressive strength of the slightly weathered pile end rock layer is f rp =45MPa, the pile end is embedded in the rock layer to a depth of 0.5 to 1m. When there are soil holes or karst caves on the pile side, the pile side friction resistance is not taken into account. According to Article 8.5.6, Paragraph 6 of the Code for Design of Building Foundations (GB 50007-2011), there should be no weak interlayers, fracture zones and caves within 3d and not less than 5m below the end of the rock-embedded cast-in-place pile, and there should be no rock face within the stress diffusion range of the pile bottom. When there is a weak structural surface in the rock mass that tends to face the face, the foundation sliding stability should be verified. When the height difference of adjacent foundations is greater than or equal to 5m, the height difference of adjacent foundations should be adjusted to be similar.

[0059] Table 2 Recommended values ​​of mechanical parameters of pile foundation (punched and bored piles, pile length ≥ 15m)

[0060]

[0061]

[0062] The preferred solution is to design a raft foundation in the pure basement and the 4-story building. The underlying rock layer at the raft foundation does not fluctuate much overall, the cave plane is distributed in a point-like manner, and the cave area is not large. After calculation, the thickness of the raft foundation is designed to be 800mm, and the use of HRB400 grade φ25 steel bars with double-layer bidirectional reinforcement can meet the bearing capacity requirements. In the anti-floating design, due to the large difference in the thickness of the covering layer in the local part of the raft foundation, some anti-floating piles need to be inserted into the rock to ensure the pull-out bearing capacity, which may lead to differences in foundation stiffness. Therefore, according to the actual situation, the method of increasing the thickness of the local raft can be used for anti-floating design.

[0063] In addition, in order to reduce the impact of additional loads on karst stability, the thickness of the karst overlying soil layer at the raft foundation should not be less than the thickness of the compression layer of the raft foundation. n It can be calculated according to Article 5.4.4 of the Technical Specifications for Raft and Box Foundations of High-Rise Buildings (JGJ 6-2011). When the thickness of the karst overlying soil layer is less than the thickness of the compression layer, the stability of the foundation should be analyzed in combination with factors such as the karst development state, cave shape, karst groundwater activity, and cave filling conditions.

[0064] The preferred solution is that when the pile position encounters karst development, mud loss and sudden drop in water level in the hole are likely to occur during the pile construction process, leading to hole collapse and ground collapse. In addition, when there is a cave within the bearing layer at the pile end, the bearing capacity and stability of the pile foundation will be greatly reduced, which may easily lead to pile foundation instability. Therefore, the karst foundation needs to be treated during the construction of engineering piles to ensure the quality and safety of the project. According to the comprehensive geophysical exploration results, on the basis of exploring the laws of karst development and the spatial relationship between the cave and the pile foundation, the following treatment methods are taken in a targeted manner:

[0065] (1) When there is a cave within a range of 3 times the pile diameter less than 5m directly below the pile end, the cave should be penetrated to reach a complete bearing layer. When the depth of the soil cave or karst cave is not more than 2.5m, the method of replacing or lowering the steel casing can be adopted. When replacing, the excavation slope ratio is not more than 1:1 or the actual stable slope. When lowering the steel casing, its height is not less than 1.5m below the cave top elevation. When the depth of the soil cave or karst cave is greater than 2.5m but less than 6m, backfilling with stone flakes and clay and small-stroke punching with a punching machine can be adopted. When the depth of the soil cave or karst cave is greater than 6m, cement slurry can be poured or filled with C20 concrete for treatment. After the strength of the cement slurry or concrete reaches 50% of the design strength, secondary rotary drilling is carried out and the skipping method is adopted for construction.

[0066] (2) When there is a karst cave within a range of less than 5m of 3 times the pile diameter below the pile end, the influence of the stress diffusion of the engineering pile on the stability of the karst cave needs to be considered. For the piles under the ground-standing shear wall or column of 7-story and 9-story buildings, the karst cave can be filled by high-pressure grouting, or the pile end can be extended to below the bottom of the karst cave. For the pile foundation under the column of the podium building and pure basement, the karst cave does not need to be treated when the top plate thickness is greater than 5m.

[0067] (3) When the bearing layer at the pile end does not meet the requirements after pile construction, the "high-pressure grouting to replace the cave filling" method can be used. This method firstly performs a comprehensive high-pressure flushing and cleaning of the filling in the cave below the pile end, flushes the clay and fine sand out of the drill hole, and uses the remaining medium and coarse sand and gravel as the aggregate of the grouting body. Subsequently, cement slurry is injected into the "void" under high pressure to form a reinforcement body with sufficient strength.

[0068] (4) When the above situation cannot be avoided, a spanning method can be used to deal with it. Two engineering piles are added on both sides of the pile foundation to be reinforced, and a support beam is used to support and replace the structure.

[0069] When there is a cave within 5m under the raft foundation, it can be replaced or filled with C35 concrete. When the depth of the cave under the raft foundation exceeds 5m, if the cave is small, the impact of the cave can be ignored, but reinforcement steel bars should be added to the raft foundation within the plane distribution range of the cave. If the cave is large, reinforced concrete beams, slabs, arches and other structural forms can be used for spanning. When using a spanning beam, ensure that the length of the beam end support on the bearing layer is not less than 1.5 times the beam height.

[0070] The embodiment of the present invention further provides a karst area foundation design system based on comprehensive geophysical exploration, and the system is used to implement a karst area foundation design method based on comprehensive geophysical exploration, which specifically includes:

[0071] The comprehensive geophysical exploration module is used to detect the karst area using a comprehensive geophysical exploration method that combines high-density resistivity method, micro-seismic detection method and elastic wave CT method to obtain the location distribution law of the karst development area;

[0072] The foundation pit excavation module is used to adjust the uneven settlement by laying a cushion layer under the base after the foundation pit is excavated;

[0073] The pile foundation module is used to adopt pile foundation at the location where the single column load is the largest. The building foundation adopts a combination of pile foundation and raft foundation.

[0074] Beneficial effects:

[0075] (1) The comprehensive geophysical prospecting method combining high-density resistivity method, micro-seismic detection method and elastic wave CT method can not only quickly delineate the development area of ​​karst caves, but also accurately locate the size and scale of karst caves, which can provide valuable reference for foundation design and foundation treatment in karst areas.

[0076] (2) The pile raft foundation has distinct advantages such as high rigidity, good integrity, and strong ability to adjust uneven settlement, and can be well applied to projects in covered karst areas.

[0077] (3) Based on the comprehensive exploration results, targeted karst foundation treatment can not only effectively solve karst engineering problems, but also save a lot of construction time and costs.

[0078] (4) Based on comprehensive geophysical exploration, this paper proposed a refined foundation design and foundation treatment method, which has achieved good application results in engineering practice and can provide experience reference and reference for similar projects.

[0079] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A karst area foundation design method based on comprehensive geophysical exploration, characterized in that: The following steps are involved: S1, the karst area is detected by a comprehensive geophysical method combining high-density resistivity method, micro-seismic detection method and elastic wave CT method to obtain the location distribution law of the karst development area; specifically: S101, using high-density resistivity method to conduct overall detection of the target area to delineate the karst development area; S102, local detection of karst development areas is carried out by micro-motion detection method to obtain the karst development range, preliminary scale and undulating form of bedrock surface, and obtain local karst development areas; S103, using elastic wave CT method to finally locate the local karst development area, and obtain the precise location, scale and burial depth of the karst; S2, after the excavation of the foundation pit, a cushion layer is laid under the base to adjust the uneven settlement; S3, pile foundation is used at the location where the single column load is the largest, and the building foundation adopts a combination of pile foundation and raft foundation.

2. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: The S3 specifically includes: The basement and 4-storey buildings use slab raft foundations, while the 7-storey and 9-storey buildings use pile foundations; The raft foundation uses the silty clay layer, silty sand layer, and residual silty clay layer at the basement floor elevation as the bearing layer, and the pile foundation uses slightly weathered marble as the basic bearing layer; Anti-floating measures are combined with foundation forms to adopt anti-floating piles or anti-pullout anchors.

3. The karst area foundation design method based on comprehensive geophysical exploration according to claim 2 is characterized in that: The S3 specifically includes: the pure basement and the 4-story building are designed as raft foundations; the raft foundations use HRB400 grade φ25 steel bars with double-layer bidirectional reinforcement to meet the bearing capacity requirements.

4. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: The thickness of the karst overlying soil layer at the raft foundation is not less than the thickness of the compression layer of the raft foundation foundation.

5. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: The S3 specifically includes: When there is a cave within a range of 3 times the pile diameter less than 5m directly below the pile end, the pile foundation penetrates the cave to reach a complete bearing layer; When the buried depth of soil cave or karst cave is not more than 2.5m, the method of replacement filling or lowering steel casing is adopted. When replacing filling, the excavation slope ratio is not more than 1:1 or the actual stable slope; when lowering the steel casing, its height is not less than 1.5m above the top elevation of the karst cave; When the depth of soil cave or karst cave is greater than 2.5m but less than 6m, backfill with stone flakes and clay and use a small-stroke punching machine to punch the hole. When the buried depth of soil cave or karst cave is greater than 6m, cement slurry is poured or filled with C20 concrete for treatment; after the strength of cement slurry or concrete reaches 50% of the design strength, secondary rotary drilling is carried out and the skip drilling method is used for construction.

6. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: The S3 specifically includes: when there is a karst cave within a range of 3 times the pile diameter less than 5m below the pile end; If the pile foundation under the ground-standing shear wall or column of the 7-story and 9-story building is filled with high-pressure grouting, or the pile end is extended below the bottom of the cave; If the pile foundation under the podium building and pure basement columns has a top slab thickness greater than 5m, the cave will not be treated.

7. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: S3 specifically includes: when the bearing layer test at the pile end after pile construction does not meet the requirements, the "high-pressure grouting to replace the cave filling" method is used for treatment, as follows: First, the filling material in the karst cave under the pile end is fully cleaned by high-pressure flushing, so that clay and fine sand can be flushed out of the drill hole to the ground, and the remaining medium and coarse sand and gravel are used as aggregates for the grouting body; Then cement slurry is injected into the cavity under high pressure to form a reinforcement.

8. The karst area foundation design method based on comprehensive geophysical exploration according to claim 1 is characterized in that: The S3 specifically includes: When there is a cave within 5m below the raft foundation, it should be replaced or filled with C35 concrete; When the depth of the cave under the raft foundation exceeds 5m, if the size of the cave is less than a certain threshold, additional reinforcement steel bars shall be added to the raft foundation within the plane distribution range of the cave; If the size of the cave is larger than a certain threshold, reinforced concrete beams, slabs, arches and other structures can be used for spanning. When using spanning beams, ensure that the length of the beam end support on the bearing layer is not less than 1.5 times the height of the beam.

9. A karst area foundation design system based on comprehensive geophysical exploration, characterized in that: The system is used to implement the karst area foundation design method based on comprehensive geophysical exploration as described in any one of claims 1 to 8, specifically comprising: The comprehensive geophysical exploration module is used to detect the karst area using a comprehensive geophysical exploration method that combines high-density resistivity method, micro-seismic detection method and elastic wave CT method to obtain the location distribution law of the karst development area; The foundation pit excavation module is used to adjust the uneven settlement by laying a cushion layer under the base after the foundation pit is excavated; The pile foundation module is used to adopt pile foundation at the location where the single column load is the largest. The building foundation adopts a combination of pile foundation and raft foundation.

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