Bridge pile karst cave section semi-flexible sleeve wrapping structure and construction method

Abstract

The invention discloses a bridge pile karst cave section semi-flexible sleeve wrapping structure and a construction method, and belongs to the technical field of bridge pile construction.The bridge pile karst cave section semi-flexible sleeve wrapping structure comprises a steel reinforcement cage, a steel reinforcement support lantern ring is arranged on the outer side of the steel reinforcement cage, a geomembrane is arranged on the outer side of the steel reinforcement support lantern ring, and a concrete protection layer is arranged between the steel reinforcement cage and the geomembrane; the mounting mode of the geomembrane comprises a local mounting mode and a full-wrapping mounting mode. According to the bridge pile karst cave section semi-flexible sleeve wrapping structure and the construction method, the restraint strap is arranged to prevent the geomembrane from being broken due to excessive deformation, excessive external expansion can be avoided, loss of cast-in-place pile slurry is reduced, materials are saved, the bearing capacity of a pile foundation is improved, the construction efficiency of the pile foundation is improved, the reinforcement cage provides restraining force for concrete, and the construction efficiency of the pile foundation is improved. Concrete is prevented from puncturing the geomembrane, the geomembrane can be supported, and the situation that the size of the geomembrane on the outer side is expanded into a pile body due to collapse of the hole wall is prevented.

Description

Technical Field

[0001] This invention relates to the field of bridge pile construction technology, and in particular to a semi-flexible sleeve wrapping structure and construction method for the karst cave section of a bridge pile. Background Technology

[0002] One of the most prominent geological features of karst landforms is the presence of numerous difficult-to-handle sinkholes and soil cavities, posing significant quality and safety risks to pile foundation construction. Construction in karst areas may encounter karst foundations with karst caves and other similar features, easily leading to insufficient bearing capacity, uneven settlement, and deformation instability. Furthermore, the complex geological conditions present numerous challenges to construction; some pile foundation boreholes collapse immediately upon drilling, requiring repeated backfilling and re-drilling, thus extending the construction period and increasing the workload and costs. Simultaneously, sinkholes and soil cavities may surround the pile foundation with potential filled or semi-filled voids, posing a significant risk to the pile foundation's safety and compromising construction safety and project quality. Summary of the Invention

[0003] The purpose of this invention is to provide a semi-flexible sleeve wrapping structure and construction method for the karst section of a bridge pile. The restraint band prevents the geomembrane from deforming and breaking excessively, and avoids excessive outward expansion. This reduces the loss of grout in the cast-in-place pile, saves materials, improves the bearing capacity of the pile foundation, and increases the construction efficiency of the pile foundation. The steel cage provides restraint for the concrete, preventing the concrete from puncturing the geomembrane. It can also support the geomembrane and prevent the outer geomembrane from expanding into the pile body size due to the collapse of the borehole wall.

[0004] To achieve the above objectives, the present invention provides a semi-flexible sleeve wrapping structure for the karst section of a bridge pile, including a reinforcing cage, a reinforcing support ring on the outside of the reinforcing cage, a geomembrane on the outside of the reinforcing support ring, and a concrete protective layer between the reinforcing cage and the geomembrane. The geomembrane can be installed in two ways: partial installation and full wrapping installation.

[0005] Preferably, in the partial installation, membrane bag buckles are evenly distributed at both ends of the geomembrane, and the membrane bag buckles are fixed to the steel reinforcement bracket collar by steel wires. The middle part of the geomembrane is fixed to the steel reinforcement bracket collar by a binding strap. In the full-coverage installation, the geomembrane is cylindrical with an open top and a closed bottom. The bottom of the geomembrane is perforated or geotextile is used as the bottom.

[0006] A construction method for a semi-flexible sleeve-wrapped structure for a karst cave section of a bridge pile includes the following steps: S1. Determine the location and size of the karst caves at the pile foundation; S2. Construction surveying and setting out; S3. Install casing; S4. Prepare mud; S5. Drilling operations; S6. Hole drilling inspection; S7. First hole cleaning; S8. Geomembrane installation; S9. Reinforcing cage hoisting; S10, catheter installation; S11, Second hole cleaning; S12, Underwater concrete pouring.

[0007] Preferably, in S1, the location and size of karst caves and soil caves at the pile foundation are accurately determined using cross-hole CT imaging, cross-hole radar detection, and tube wave detection.

[0008] Preferably, during the drilling process in S5, the geological conditions of the borehole should be checked frequently and the changes in the coating should be recorded and compared with the geological profile map. The observation data should be recorded regularly by designated personnel. Different drilling speeds and pressures should be used for different soil layers. Attention should be paid to the changes in the strata. Cutting samples should be collected at the locations of changes in the strata, the geological type should be determined and recorded in the record table, and compared with the geological profile map provided in the design. The cutting samples should be numbered and stored.

[0009] Preferably, the installation of the geomembrane in S8 should be based on the location and size of the karst caves and soil caves at the test pile determined by the cross-hole CT scan, as well as the type of pile foundation, and a partial installation or full-coverage installation scheme should be selected.

[0010] Therefore, the present invention adopts the above-mentioned semi-flexible sleeve wrapping structure and construction method for the karst section of bridge piles. The restraint belt is set to prevent the geomembrane from deforming too much and breaking, and to avoid excessive outward expansion. This reduces the loss of grout in the cast-in-place pile, saves materials, improves the bearing capacity of the pile foundation, and improves the construction efficiency of the pile foundation. The steel cage provides restraint for the concrete, prevents the concrete from puncturing the geomembrane, and can also support the geomembrane to prevent the outer geomembrane from expanding into the pile body size due to the collapse of the borehole wall.

[0011] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1 This is a front view of an embodiment of the semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section according to the present invention; Figure 2 This is a cross-sectional view of an embodiment of the semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section according to the present invention; Figure 3 This is a schematic diagram of the on-site investigation using cross-hole CT imaging method, representing an embodiment of the semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section according to the present invention. Figure 4 This is a schematic diagram of the field survey of the pipe wave detection method in an embodiment of the semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section according to the present invention. Figure 5 This is a schematic diagram of the field survey of the cross-hole radar detection method in an embodiment of the present invention, which describes a semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section. Figure 6 This is a schematic diagram of the membrane bag installation in an embodiment of the semi-flexible sleeve wrapping structure and construction method for a bridge pile karst section according to the present invention.

[0013] Figure Labels 1. Reinforcing cage; 2. Reinforcing bar support ring; 3. Geomembrane; 4. Restraint strap; 5. Concrete protective layer; 6. Membrane bag buckle. Detailed Implementation

[0014] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0016] Example 1 As shown in the figure, this invention provides a semi-flexible sleeve-wrapping structure for the karst cave section of a bridge pile, including a reinforcing cage 1. The reinforcing cage 1 enhances the tensile strength of the bridge pile. Since concrete has high compressive strength but low tensile strength, a reinforcing cage 1 is needed during bridge pile casting to increase the tensile strength. Furthermore, the reinforcing cage 1 provides constraint to the concrete, preventing it from puncturing the geomembrane 3, and also supports the geomembrane 3, preventing it from expanding into the pile size due to borehole wall collapse. A reinforcing cage support ring 2 is provided on the outside of the reinforcing cage 1. A 5cm thick reinforcing cage support ring 2 is welded at the corresponding position of the reinforcing cage 1 within two meters above and below the detected karst cave location to prevent the geomembrane 3 from adhering tightly to the reinforcing cage 1 during casting. A geomembrane 3 is provided on the outside of the reinforcing cage support ring 2, and a concrete protective layer 5 is provided between the reinforcing cage 1 and the geomembrane 3. The concrete protective layer 5 prevents the karst cave from collapsing, and the reinforcing cage support ring 2 ensures the thickness of the concrete protective layer 5.

[0017] The geomembrane 3 can be installed in two ways: partial installation and full-coverage installation. In partial installation, both ends of the geomembrane 3 are evenly distributed with membrane bag buckles 6, which are fixed to the steel reinforcement support rings 2 by steel wires. The membrane bag buckles 6 facilitate the installation of both ends of the geomembrane 3 onto the steel reinforcement support rings 2. The middle part of the geomembrane 3 is fixed to the steel reinforcement support rings 2 by a binding strap 4. The binding strap 4 ensures that the geomembrane 3 is tightly connected to the steel reinforcement cage 1 and the steel reinforcement support rings 2, preventing displacement or deformation during the grouting process and preventing the geomembrane 3 from breaking due to excessive deformation. In full-coverage installation, the geomembrane 3 is cylindrical with an open top and a closed bottom. The bottom of the geomembrane is perforated or geotextile is used as the bottom to prevent excessive buoyancy from preventing the membrane bag from being lowered.

[0018] A construction method for a semi-flexible sleeve-wrapped structure for a karst cave section of a bridge pile includes the following steps: S1. Determine the location and size of the karst caves at the pile foundation; To ensure that the geomembrane 3 effectively covers the locations of karst caves and soil cavities, cross-hole CT imaging, cross-hole radar detection, and tube wave detection are used to accurately determine the location and size of karst caves and soil cavities at the pile foundation. Cross-hole CT imaging typically uses two boreholes with a fan-shaped receiver (one transmitter, multiple receivers). After excitation at several points (electric spark or explosive), a dense ray network is formed within the observation area. Tube wave detection uses a single-transmitter, single-receiver, single-hole detection device with a fixed transmitter-receiver distance. Cross-hole detection involves placing transmitting and receiving antennas in two separate boreholes. In cross-hole mode, the transmitting and receiving antennas are arranged in different boreholes. To minimize the influence of geometric position, the two boreholes are ideally located in the same two-dimensional plane, and the medium to be investigated is located between the two boreholes, thus achieving high precision and accuracy. Furthermore, during engineering surveys, at least three survey holes should be set within the diameter range of the drilled pile location to accurately determine the location and size of karst caves and soil cavities, ensuring that the geomembrane 3 effectively covers them.

[0019] S2. Construction surveying and setting out; Before construction layout and surveying, a survey control network shall be set up as required, and the centerline stakes and benchmarks of bridges and culverts required during construction shall be supplemented. After the site is leveled, the coordinate points of the stakes shall be accurately laid out. After the layout, the relative positions of the centers of each stake shall be checked and measured. After the check is correct, the protective stakes shall be laid out in a timely manner.

[0020] S3. Install casing; When the topsoil is loose, the casing should be buried at least 50cm into a firmer, denser soil layer, and the casing should be backfilled with clay in layers and compacted. The allowable deviations for casing installation and the inspection methods are shown in Table 1.

[0021] Table 1 Allowable Deviations and Inspection Methods for Casing Installation

[0022] S4. Prepare mud; The mud used in the mud pit is made from bentonite, soda ash, and other high-quality materials. The mud properties are adjusted promptly according to the geological conditions. Prefabricated mud pits and sedimentation tanks are placed near the pile hole and connected by circulation hoses. The mud circulation sequence is: freshly prepared mud - mud pit - pile hole - sedimentation tank - mud pit - pile hole. The mud is made from bentonite, and its performance indicators must meet the requirements of Table 2.

[0023] Table 2 Mud Performance Indicators

[0024] S5. Drilling operations; During drilling, the geological conditions of the borehole should be checked frequently and the changes in the coating should be recorded and compared with the geological profile map. Observation data should be recorded regularly by designated personnel. Different drilling speeds and pressures should be used for different soil layers. Pay attention to changes in the strata and collect cuttings samples at the points of strata change. Determine the geological type and record it in the record table. Compare it with the geological profile map provided in the design. Number and save the cuttings samples for analysis and future reference.

[0025] S6. Hole drilling inspection; When the drilling depth reaches the design requirements, the hole depth, hole diameter, hole center and hole shape are checked. The inspection method is to use a hole inspection tool. Only after confirming that the design requirements are met can subsequent work be carried out.

[0026] S7. First hole cleaning; After drilling to the designed depth, the cuttings removal time with the rotary drilling rig is relatively extended, but no pressure is applied to ensure that all drilling cuttings are removed while avoiding over-drilling. If the relative density of the drilling mud is too high, a high-pressure water pipe is inserted into the bottom of the hole to wade through the water until the mud performance indicators meet the requirements. The performance indicators and sediment thickness requirements for the first hole cleaning mud are as follows: specific gravity not greater than 1.1, sand content less than 2%, and viscosity 17s-20s.

[0027] S8. Geomembrane installation; The installation of geomembrane 3 should be based on the location and size of karst caves and soil cavities at the test pile determined by cross-hole CT scanning, as well as the type of pile foundation, to select an appropriate installation scheme. When using a partial installation scheme, geomembrane 3 should be installed in the rock strata below the bottom of the soil layer and above the bearing layer. A minimum 3m penetration depth into the rock layer should be reserved in the bearing layer to meet the requirements of the pile foundation's compressive strength, tensile strength, and bearing capacity. When using a full-coverage installation scheme, the geomembrane 3 near the karst cave should be appropriately reinforced. Simultaneously, holes should be made at the bottom of the geomembrane 3 sleeve, or geotextile should be used as the bottom to prevent excessive buoyancy that would prevent the geomembrane 3 from being lowered. A schematic diagram of the geomembrane 3 installation is shown below. Figure 6 As shown, Figure 6 (a) in the diagram represents a partial installation scheme. Figure 6 (b) in the diagram represents the fully enclosed installation scheme.

[0028] After determining the installation plan, install the steel reinforcement support rings 2 for fixing the geomembrane 3 at the corresponding positions on the reinforcing cage 1. The steel reinforcement support rings 2 are made of welded steel bars, and their dimensions should allow sufficient clearance for the pile body concrete protective layer 5 during pile formation. During partial installation, the steel reinforcement support rings 2 should be welded 0.5-1m above and below the corresponding karst cave position on the reinforcing cage to prevent displacement or deformation of the geomembrane 3 from affecting the pile formation effect. After welding the steel reinforcement support rings 2 to the reinforcing cage 1, use steel wire to connect and fix the geomembrane 3 to the steel reinforcement support rings 2 onto the reinforcing cage 1.

[0029] S9. Reinforcing cage hoisting; When inserting the reinforcing cage 1 into the borehole, a spreader-type hoist is used to prevent unevenness and deformation due to tightening. A spreader-type hoisting point is set at the top of the reinforcing cage 1, and another hoisting point is set at one-third of the distance from the bottom of the reinforcing cage 1. The reinforcing cage 1 is hoisted into the borehole as a whole, avoiding contact with the borehole wall during the hoisting process to prevent the borehole wall from collapsing or puncturing the geomembrane 3. After the reinforcing cage 1 is installed, the pile center is positioned using a string line method. Four positioning bars are symmetrically set every two meters on the pile foundation reinforcing cage 1, evenly distributed around the pile foundation reinforcing bars. Three ultrasonic testing tubes with an outer diameter of Φ53*1.8 are evenly distributed on each pile foundation, and the testing tubes are all connected by snap-fit.

[0030] S10, catheter installation; The guide pipe uses Φ0.3m steel tubing with a smooth, rounded inner wall, uniform inner diameter, and tight joints. The middle section is 3m long, the bottom section can be 4m, and 1m or 0.5m long tubing is used below the funnel. Before use, the guide pipes undergo trial assembly and watertightness tests, and are numbered and marked in ascending order. After assembly, the axial deviation of the guide pipe should not exceed 0.5% of the borehole depth and should not exceed 10cm. The test pressure is 1.5 times the hydrostatic pressure at the bottom of the borehole. The length of the guide pipe is determined by the borehole depth and the height of the working platform. The guide pipe uses a spiral threaded joint and is equipped with a release device.

[0031] For first-time use, a watertight test is required for the conduit. Only conduits that pass the test can be used. The conduits are numbered from bottom to top according to the assembly sequence during the test. During on-site assembly, sections are assembled one by one according to the assembly sequence of the pressure test. The conduit is placed in the center of the borehole, and a lifting test is conducted before pouring concrete. The lifting capacity of the conduit hoisting equipment is compatible with the total weight and friction of the entire conduit after it is filled with concrete, and has a certain safety margin. The distance between the bottom of the conduit and the bottom of the borehole is controlled at 40cm, ensuring that the water-stop ball or other water-stopping material can be smoothly discharged outside the conduit after falling to the bottom opening. The concrete pouring support is made of structural steel to support the suspended conduit, and the funnel for pouring concrete is placed on top.

[0032] S11, Second hole cleaning; After the guide pipe is installed, the sediment at the bottom of the borehole is measured again. If the sediment thickness does not meet the requirements, a second cleaning of the borehole is required. For mud-wall drilling, after the guide pipe is installed, mud is pumped into the bottom of the borehole to replace the mud containing suspended drill cuttings. During the cleaning process, mud parameters are frequently checked. Continuous circulation and purification are maintained until the mud discharged from the borehole meets the following parameters: no 2-3mm particles in the discharged or extracted mud, mud specific gravity not exceeding 1.1, sand content less than 2%, viscosity 17s-20s, and sediment thickness at the bottom of the borehole not exceeding 5cm for column piles and not exceeding 20cm for friction piles. The next procedure can only proceed after the supervising engineer has inspected and approved the results. Underwater concrete is poured immediately after the second cleaning to prevent the mud from settling again. For dry-drilled boreholes, the entire reinforcing cage 1 is lifted out. A rotary drilling rig with a cutting bucket is used to clean the sediment at the bottom of the pile. After re-measurement and approval, the reinforcing cage 1 is re-lifted and installed.

[0033] S12, Underwater concrete pouring; After the hole cleaning is completed and meets the requirements, the pile body concrete should be poured immediately.

[0034] Therefore, the present invention adopts the above-mentioned semi-flexible sleeve wrapping structure and construction method for the karst section of bridge piles. The restraint belt is set to prevent the geomembrane from deforming too much and breaking, and to avoid excessive outward expansion. This reduces the loss of grout in the cast-in-place pile, saves materials, improves the bearing capacity of the pile foundation, and improves the construction efficiency of the pile foundation. The steel cage provides restraint for the concrete, prevents the concrete from puncturing the geomembrane, and can also support the geomembrane to prevent the outer geomembrane from expanding into the pile body size due to the collapse of the borehole wall.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A semi-flexible sleeve wrapping structure for karst sections of bridge piles, characterized in that: The system includes a reinforcing cage, a reinforcing support collar on the outside of the reinforcing cage, a geomembrane on the outside of the reinforcing support collar, and a concrete protective layer between the reinforcing cage and the geomembrane. The geomembrane can be installed in two ways: partial installation and full-coverage installation.

2. The semi-flexible sleeve wrapping structure for the karst section of a bridge pile according to claim 1, characterized in that: In the partial installation, the geomembrane has membrane bag buckles at both ends, and the membrane bag buckles are fixed to the steel reinforcement bracket collar by steel wire. The middle part of the geomembrane is fixed to the steel reinforcement bracket collar by a binding strap. In the full-coverage installation, the geomembrane is cylindrical with an open top and a closed bottom. The bottom of the geomembrane is perforated or geotextile is used as the bottom.

3. A construction method for a semi-flexible sleeve-wrapping structure for a bridge pile karst section as described in any one of claims 1-2, characterized in that: Includes the following steps: S1. Determine the location and size of the karst caves at the pile foundation; S2. Construction surveying and setting out; S3. Install casing; S4. Prepare mud; S5. Drilling operations; S6. Hole drilling inspection; S7. First hole cleaning; S8. Geomembrane installation; S9. Reinforcing cage hoisting; S10, catheter installation; S11, Second hole cleaning; S12, Underwater concrete pouring.

4. The construction method of a semi-flexible sleeve wrapping structure for a bridge pile karst section according to claim 3, characterized in that: In S1, the location and size of karst caves and soil caves at the pile foundation are accurately determined using cross-hole CT imaging, cross-hole radar detection, and tube wave detection.

5. The construction method of a semi-flexible sleeve wrapping structure for a bridge pile karst section according to claim 3, characterized in that: During the drilling process in S5, the geological conditions of the borehole should be checked frequently and the changes in the coating should be recorded and compared with the geological profile map. The observation data should be recorded regularly by designated personnel. Different drilling speeds and pressures should be used for different soil layers. Attention should be paid to the changes in the strata. Cutting samples should be collected at the locations of strata changes, the geological type should be determined and recorded in the record table, and compared with the geological profile map provided in the design. The cutting samples should be numbered and stored.

6. The construction method of a semi-flexible sleeve wrapping structure for a bridge pile karst section according to claim 3, characterized in that: The installation of the geomembrane in S8 should be based on the location and size of the karst caves and soil caves at the test pile determined by the cross-hole CT scan, as well as the type of pile foundation, to select a partial installation or full-coverage installation scheme.

Images