Karst area cast-in-situ bored pile foundation construction tool and construction method thereof

Abstract

The invention discloses a karst area cast-in-situ bored pile foundation construction tool and a construction method thereof, and relates to the technical field of geotechnical engineering. The lower steel casing is coaxially arranged under the upper steel casing at intervals; the pile casing top bracket is positioned at the top of the upper steel pile casing; the pile casing bottom annular track is arranged on the inner wall of the bottom of the upper steel pile casing; the pile casing bottom sliding block is arranged on the pile casing bottom annular track in a sliding manner; the telescopic scanning bracket is arranged at the bottom of the sliding block at the bottom of the protective cylinder; the scanning base is arranged at the bottom end of the scanning bracket; the 3D printing scanning head and the 3D printing spray head are arranged on the side, away from the center shaft of the upper steel casing, of the scanning base; a 3D printing supply pipeline; a 3D printing control end; and a 3D printing feeding end. The 3D printing technology is adopted for constructing the high-strength isolation body, the high-strength isolation body conforms to the complex karst cave form, the karst cave environment which is difficult to deal with through a traditional method can be effectively treated, the pile forming safety, reliability and efficiency are remarkably improved, and the pile side friction resistance and the pile foundation bearing capacity are improved through combination of the isolation body and the pile foundation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, in particular to a bored pile foundation construction tool in karst area and a construction method thereof. BACKGROUND

[0002] Karst landforms are widely distributed in the southwest of China. In the engineering construction of karst areas, there are problems of foundation stability and collapse, and the measure of reinforcing the foundation is usually adopted. The most commonly used foundation form is pile foundation.

[0003] Due to the complex hydrogeological conditions in karst areas, the spatial distribution of karst caves and soil caves is complex, which has a very adverse effect on pile foundation construction. Specifically, (1) the poured concrete in the pile forming process is prone to loss when encountering connected holes such as karst caves, causing huge economic losses; (2) problems such as necking, diameter change and broken pile are prone to occur, which seriously affect the pile forming quality; (3) when there are multiple karst caves and soil caves on the side of the pile, the side friction of the pile will be reduced, causing insufficient bearing capacity of the pile foundation and endangering the safety of the building. Although the existing technology has made great contributions in solving the problems faced by pile foundation construction in karst areas, it still has certain problems in construction cost, difficulty, time and applicability, such as the problems of non-dense filling, poor form adaptability, etc. in the case of backfilling with stone clay, and the problems of easy leakage of concrete pouring and non-recyclability of steel casings used in the case of using steel casings to protect the concrete pouring in the karst cave.

[0004] In view of the defects such as non-dense filling, poor form adaptability, low efficiency and uncontrollable effect of the conventional methods (such as grouting filling, casing following, backfilling with stone clay, etc.), especially the problems of poor effect on irregular karst caves, insufficient side friction of the pile and insufficient bearing capacity of the pile foundation, a pile foundation construction technology in karst area is provided. SUMMARY

[0005] In view of the defects in the prior art, the purpose of the present application is to provide a pile foundation construction tool in karst area and a construction method thereof, which uses 3D printing technology to construct a high-strength isolation body that fits the complex karst cave form, realizes isolation, avoids excessive filling, effectively overcomes the limitations of traditional methods, can effectively deal with the karst cave environment that traditional methods cannot cope with, significantly improves the safety, reliability and efficiency of pile forming, and improves the side friction of the pile and the bearing capacity of the pile foundation through the combination of the isolation body and the pile foundation.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a pile foundation construction tool in karst area, which comprises:

[0008] an upper steel casing extending into the top of the target karst cave from the ground in the area where the target karst cave is located;

[0009] a lower steel casing passing through the bottom of the target karst cave from the inside of the target karst cave, the lower steel casing being coaxially spaced below the upper steel casing;

[0010] a casing top bracket arranged on the ground where the target karst cave is located and located at the top of the upper steel casing;

[0011] a casing bottom annular track arranged on the inner wall of the bottom of the upper steel casing;

[0012] a casing bottom slider slidingly arranged on the casing bottom annular track;

[0013] a telescopic scanning bracket arranged at the bottom of the casing bottom slider;

[0014] a scanning base arranged at the bottom end of the telescopic scanning bracket;

[0015] a 3D printing scanning head and a 3D printing nozzle arranged on the side of the scanning base away from the central axis of the upper steel casing;

[0016] a 3D printing supply pipeline extending from the casing top bracket into the upper steel casing, sequentially passing through the casing bottom slider and the telescopic scanning bracket, and extending into the scanning base, wherein one end of a 3D printing communication pipeline built in the 3D printing supply pipeline is signal connected with the 3D printing scanning head and the 3D printing nozzle in the target karst cave, and one end of a 3D printing supply pipeline built in the 3D printing supply pipeline is in communication with the 3D printing nozzle in the target karst cave;

[0017] a 3D printing control end signal connected with the casing bottom slider and the telescopic scanning bracket at one end of the 3D printing communication pipeline on the ground where the target karst cave is located;

[0018] a 3D printing supply end in communication with one end of the 3D printing supply pipeline on the ground where the target karst cave is located and signal connected with the 3D printing control end.

[0019] On the basis of the above technical solution, the 3D printing communication pipeline is a flexible cable.

[0020] On the basis of the above technical solution, the 3D printing supply pipeline is a telescopic pipeline.

[0021] On the basis of the above technical solution, the casing bottom annular track has a cross-section in the shape of an I-beam.

[0022] On the basis of the above technical solution, the casing bottom annular track is arranged on the inner wall of the bottom of the upper steel casing by a plurality of symmetrically distributed bolts.

[0023] In a second aspect, the application provides a construction method of the construction tool for the bored pile foundation in the karst area according to the first aspect, and the method comprises the following steps:

[0024] detecting the position of the target cave, and vertically driving a preset upper steel casing from the ground corresponding to the position of the target cave until the upper steel casing passes through the top of the target cave; and drilling through the area of the top of the target cave surrounded by the upper steel casing;

[0025] driving a lower steel casing with a preset size smaller than the upper steel casing into the top of the target cave until the lower steel casing is coaxially arranged below the upper steel casing, and drilling through the area of the bottom of the target cave surrounded by the lower steel casing, wherein the bottom of the lower steel casing is located inside the bottom of the target cave;

[0026] arranging a 3D printing scanning head and a 3D printing nozzle in the target cave;

[0027] controlling the 3D printing scanning head to measure the internal structure of the target cave to obtain the internal topography of the target cave;

[0028] obtaining the structure information of the isolation body based on the three-dimensional geological model, the positions of the upper steel casing and the lower steel casing in the target cave, and the internal topography of the target cave;

[0029] constructing the isolation body in the target cave by the 3D printing nozzle based on the structure information of the isolation body;

[0030] after the construction of the isolation body is completed, hoisting a steel reinforcement cage in the area surrounded by the upper steel casing, the lower steel casing and the isolation body, and pouring the bored pile; wherein,

[0031] the isolation body is a cylindrical structure, the bottom of which starts from the connection between the lower steel casing and the bottom of the target cave, and the top of which ends at the connection between the upper steel casing and the top of the target cave;

[0032] the outer walls of the upper steel casing and the lower steel casing are in contact with the inner wall of the isolation body.

[0033] On the basis of the above technical solution, the 3D printing nozzle constructs the isolation body in the target cave based on the structure information of the isolation body, which comprises the following steps:

[0034] the 3D printing nozzle starts to construct the isolation body from the connection between the lower steel casing and the bottom of the target cave;

[0035] When the top of the isolation body is close to the bottom end of the upper steel casing, the upper steel casing is lifted, and the 3D printing nozzle continues to build the isolation body;

[0036] When the top of the isolation body is in contact with the top of the target karst cave, the upper steel casing is restored to the original position.

[0037] On the basis of the above technical solutions, the bottom of the reinforcement cage is lower than the bottom of the target karst cave and is located in the lower steel casing.

[0038] Compared with the prior art, the application has the following advantages:

[0039] The application uses 3D printing technology to build a high-strength isolation body that fits the complex karst cave morphology, realizes isolation, avoids excessive filling, effectively overcomes the limitations of traditional methods, can effectively handle karst cave environments that are difficult to deal with by traditional methods, significantly improves the safety, reliability and efficiency of pile forming, and improves the pile side friction and pile foundation bearing capacity through the combination of the isolation body and the pile foundation. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 It is a construction schematic diagram of the rock dissolution area bored pile foundation construction tool of the embodiment of the application;

[0042] Figure 2 It is an assembly structure schematic diagram of the upper steel casing, the casing bottom annular track and the casing bottom sliding block in the rock dissolution area bored pile foundation construction tool of the embodiment of the application;

[0043] Figure 3 It is a cross-sectional view of the assembly structure of the upper steel casing, the casing bottom annular track and the casing bottom sliding block in the rock dissolution area bored pile foundation construction tool of the embodiment of the application;

[0044] Figure 4 It is a structure schematic diagram of the 3D printing supply pipeline in the rock dissolution area bored pile foundation construction tool of the embodiment of the application;

[0045] Figure 5 It is an internal structure schematic diagram of the 3D printing supply pipeline in the rock dissolution area bored pile foundation construction tool of the embodiment of the application;

[0046] Figure 6A position diagram of the isolation body in actual construction of the pile foundation construction tool for the karst area of the embodiment of the application;

[0047] Figure 7 A position diagram of the reinforcement cage in actual construction of the pile foundation construction tool for the karst area of the embodiment of the application;

[0048] Figure 8 A position diagram of the cast-in-place pile in actual construction of the pile foundation construction tool for the karst area of the embodiment of the application;

[0049] In the figure:

[0050] 1, upper steel casing; 2, lower steel casing; 3, 3D printing scanning head; 4, 3D printing nozzle; 5, casing top support; 6, casing bottom ring track; 7, casing bottom sliding block; 8, telescopic scanning support; 9, scanning base; 10, 3D printing supply pipeline; 11, 3D printing communication pipeline; 12, 3D printing feeding pipeline; 13, 3D printing control end; 14, 3D printing feeding end; A, isolation body; B, reinforcement cage; C, cast-in-place pile. DETAILED DESCRIPTION

[0051] To make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the application.

[0052] The embodiments of the application will be further described below with reference to the drawings.

[0053] The embodiments of the application provide a pile foundation construction tool for a karst area and a construction method thereof. A high-strength isolation body is constructed by using a 3D printing technology, which fits the complex cave shape, realizes isolation, avoids excessive filling, effectively overcomes the limitations of traditional methods, can effectively deal with the cave environment that is difficult to cope with by traditional methods, and significantly improves the safety, reliability and efficiency of pile forming.

[0054] To achieve the above technical effects, the general idea of the application is as follows:

[0055] A pile foundation construction tool for a karst area, the construction tool comprising:

[0056] an upper steel casing 1 extending into the top of the target cave from the ground in the area where the target cave is located;

[0057] A lower steel casing 2 passing through the bottom of the target karst cave from the inside of the target karst cave, the lower steel casing 2 being coaxially spaced below the upper steel casing 1;

[0058] A casing top bracket 5 arranged on the ground in the area where the target karst cave is located and located at the top of the upper steel casing 1;

[0059] A casing bottom annular track 6 arranged on the inner wall of the bottom of the upper steel casing 1;

[0060] A casing bottom slider 7 slidingly arranged on the casing bottom annular track 6;

[0061] A retractable scanning bracket 8 arranged at the bottom of the casing bottom slider 7;

[0062] A scanning base 9 arranged at the bottom end of the retractable scanning bracket 8;

[0063] A 3D printing scanning head 3 and a 3D printing nozzle 4 arranged on the side of the scanning base 9 away from the central axis of the upper steel casing 1;

[0064] A 3D printing supply pipeline 10 extending from the casing top bracket 5 into the upper steel casing 1, sequentially passing through the casing bottom slider 7 and the retractable scanning bracket 8, and extending into the scanning base 9, a 3D printing communication pipeline 11 arranged in the 3D printing supply pipeline 10 being signal connected to the 3D printing scanning head 3 and the 3D printing nozzle 4 in the target karst cave, and a 3D printing supply pipeline 12 arranged in the 3D printing supply pipeline 10 being in communication with the 3D printing nozzle 4 in the target karst cave;

[0065] A 3D printing control end 13 signal connected to the 3D printing communication pipeline 11 at the ground in the area where the target karst cave is located, the casing bottom slider 7, and the retractable scanning bracket 8;

[0066] A 3D printing supply end 14 in communication with the 3D printing supply pipeline 12 at the ground in the area where the target karst cave is located and signal connected to the 3D printing control end 13.

[0067] The embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0068] In a first aspect, referring to Figures 1-8 The embodiments of the present application provide a construction tool for bored pile foundation in karst area, which comprises:

[0069] An upper steel casing 1 extending into the top of the target karst cave from the ground in the area where the target karst cave is located;

[0070] a lower steel casing 2 passing through the bottom of the target cave from the inside of the target cave, the lower steel casing 2 being coaxially and spacedly arranged below the upper steel casing 1;

[0071] a casing top bracket 5 arranged on the ground where the target cave is located and at the top of the upper steel casing 1;

[0072] a casing bottom annular track 6 arranged on the inner wall of the bottom of the upper steel casing 1;

[0073] a casing bottom slider 7 slidingly arranged on the casing bottom annular track 6;

[0074] a retractable scanning bracket 8 arranged at the bottom of the casing bottom slider 7;

[0075] a scanning base 9 arranged at the bottom end of the retractable scanning bracket 8;

[0076] a 3D printing scanning head 3 and a 3D printing nozzle 4 arranged on the side of the scanning base 9 away from the central axis of the upper steel casing 1;

[0077] a 3D printing supply pipeline 10 extending from the casing top bracket 5 into the upper steel casing 1, sequentially passing through the casing bottom slider 7 and the retractable scanning bracket 8, and extending into the scanning base 9, a 3D printing communication pipeline 11 built in the 3D printing supply pipeline 10 being signal connected with the 3D printing scanning head 3 and the 3D printing nozzle 4 at one end in the target cave, and a 3D printing supply pipeline 12 built in the 3D printing supply pipeline 10 being in communication with the 3D printing nozzle 4 at one end in the target cave;

[0078] a 3D printing control end 13 signal connected with the 3D printing communication pipeline 11 at one end on the ground where the target cave is located, the casing bottom slider 7 and the retractable scanning bracket 8;

[0079] a 3D printing supply end 14 in communication with the 3D printing supply pipeline 12 at one end on the ground where the target cave is located and signal connected with the 3D printing control end 13.

[0080] It should be noted that the 3D printing control end 13 can perform the following actions with the help of the 3D printing scanning head 3:

[0081] collecting real-time sensing data reflecting the geological conditions of the hole wall during the pile foundation drilling process;

[0082] constructing and / or updating a three-dimensional geological model around the hole in real time based on the sensing data;

[0083] According to the three-dimensional geological model, the positions, sizes and stability states of karst caves and fissures are identified;

[0084] The positions, sizes and three-dimensional shapes of target karst caves at the pile foundation are verified, and the CT scanning data in the hole and other exploration data are imported into BIM / GIS software to construct an accurate three-dimensional geological model containing information of karst caves, geological stratification, fissures and underground water, and generate a three-dimensional digital model of the karst cave.

[0085] A closed isolation structure body matching the shape of the karst cave is 3D printed in situ in the karst cave, and pre-tensioned steel bars are arranged at intervals along the height during the printing process for connection with the steel reinforcement cage.

[0086] The technical solution has small influence on the karst cave environment, does not need to be filled and treated, has good adaptability to irregular karst cave shapes, is multifunctional in isolation, support and anti-seepage, and can recycle the steel casing, and the pile side friction and pile bearing capacity are improved by the combination of the isolation body and the pile foundation.

[0087] The embodiments of the present application are aimed at the defects of conventional methods (such as grouting filling, casing following, backfilling stone clay, etc.), such as non-dense filling, poor shape adaptability, low efficiency, uncontrollable effect, especially poor effect on irregular karst caves, insufficient pile side friction and pile bearing capacity, etc., and use 3D printing technology to construct a high-strength isolation / support / anti-seepage structure body in situ and on demand, which fits the complex karst cave shape, fills / isolates without dead angles, avoids excessive filling, greatly reduces the risk of slurry leakage, hole collapse and concrete loss, effectively overcomes the limitations of traditional methods, significantly improves the safety, reliability and efficiency of pile forming, has small disturbance to the surrounding rock-soil body, and can effectively handle karst caves with extremely irregular shape, special location (such as directly below the pile end), large size or strong connectivity, which are difficult to deal with by traditional methods.

[0088] Specifically, the 3D printing supply pipeline 10 is internally provided with a 3D printing communication pipeline 11 and a 3D printing supply pipeline 12;

[0089] In order to meet the actual needs, the 3D printing supply pipeline 10 is divided into a horizontal section 100, a first vertically adjustable length section 101, a vertically standard section 102 and a second vertically adjustable length section 103, so as to adapt to the construction ring needs.

[0090] Of course, the 3D printing communication pipeline 11 and the 3D printing supply pipeline 12 inside the 3D printing supply pipeline 10 can be adjusted.

[0091] It should be emphasized that the technical solution of the embodiments of the present application is used for the construction of cast-in-place piles in karst development areas, and the pile pouring does not consume a large amount of concrete to fill the karst cave.

[0092] The technical scheme of the embodiment of the present application is suitable for complex karst cave morphology, avoids overfilling, greatly reduces the risk of slurry leakage, hole collapse and concrete loss, effectively overcomes the limitations of traditional methods, significantly improves the safety, reliability and efficiency of pile forming, has small disturbance to surrounding rock and soil, and can effectively handle extremely irregular morphology, special location (such as directly below the pile end), super-large or connected karst caves that are difficult to deal with by traditional methods;

[0093] Through integral pouring of the isolation body and the pile body, the pile body is better and more closely engaged with the bedrock in the karst area to jointly bear, the pile forming quality and the single pile bearing capacity of the construction bored pile in the complex geology are improved, the isolation-supporting-anti-seepage multifunctional integration is realized, and the pile side friction and the pile foundation bearing capacity are improved through the combination of the isolation body and the pile foundation.

[0094] Further, the 3D printing communication pipeline 11 is a flexible cable.

[0095] Further, the 3D printing feeding pipeline 12 is a telescopic pipeline.

[0096] Further, the cross section of the bottom annular track 6 of the casing is an I-shaped cross section.

[0097] Further, the bottom annular track 6 of the casing is arranged in the inner wall of the bottom of the upper steel casing 1 through a plurality of symmetrically distributed bolts.

[0098] In summary, in view of the problems of poor filling and poor morphology adaptability in traditional karst treatment, the core process of the embodiment of the present application is:

[0099] 1) A borehole radar and a hole CT scan are used to construct a three-dimensional digital model of the karst cave;

[0100] 2) A multi-degree-of-freedom 3D printing device is lowered to the position of the karst cave, and a quick-setting cement-based material is sprayed in situ to form a closed isolation structure body that matches the shape of the cavity;

[0101] 3) After the strength of the isolation body meets the standard, drilling is continued to the bearing layer to complete the pile foundation construction.

[0102] The innovation of the embodiment of the present application is:

[0103] Based on the 3D printing forming technology, the morphology adaptive isolation and the accurate additive manufacturing in the underground complex environment are realized;

[0104] An integrated process of "model driven-adaptive printing-pile foundation cooperation" is proposed to solve the problems of concrete loss and hole wall instability;

[0105] It is suitable for karst foundation pile engineering of bridges, buildings and the like.

[0106] It should be noted that the technical solutions of the embodiments of the present application have the following technical details:

[0107] First, the material of the isolation body A is a fast-setting cement-based composite material, which has the following characteristics:

[0108] Pumpability and extrudability: suitable for remote delivery and in-hole extrusion;

[0109] Fast setting and early strength: rapid strength development, reducing waiting time;

[0110] Micro-expansion: compensating for shrinkage, ensuring tight bonding with the hole wall;

[0111] Good adhesion: firm adhesion with surrounding rock and subsequent pile body concrete;

[0112] Durability: resistant to seepage and erosion.

[0113] It should be noted that the matters needing attention in actual operation also include:

[0114] During drilling construction, the upper non-karst area of the cave is constructed by the conventional method, and the upper karst area of the cave is constructed by the rotary drilling rig;

[0115] A throttle control valve is arranged on the conduit of the feeding system to control the printing speed and printing quality in cooperation with the real-time monitoring devices at the ends of the feeding system and the 3D printing equipment;

[0116] After cleaning the pile hole area and forming the middle pile hole, the lower pile hole is formed by the rotary drilling method at the bottom of the cave.

[0117] Furthermore, the 3D printing equipment can be a six-axis waterproof robot, which integrates a material extrusion nozzle, a laser positioning module (precision ±2mm), and a pressure-resistant feeding system (pressure resistance ≥1MPa);

[0118] In-hole / dome 3D printing equipment: miniaturization, modularization, resistance to harsh environments (moisture, dust, vibration), with a multi-degree-of-freedom mechanical arm, carrying a printing nozzle, a material conveying pipe, a positioning system (such as laser scanning, inertial navigation, sonar), and a power supply (battery or cable);

[0119] Ground control and feeding system: control robot movement, material mixing and pumping, real-time monitoring of printing process.

[0120] Based on the technical solutions of the embodiments of the present application, the isolation body is printed and embedded in the drilling process of the cast-in-place pile foundation to form a "exploration → printing isolation → drilling → pile forming" karst pile foundation cooperative integrated construction technology. In specific implementation, the details are as follows:

[0121] Before pile forming, advanced drilling and tube wave detection are performed to determine the position of the cave and the depth of the bearing layer.

[0122] Burying the upper steel casing: installing the drilling machine, adjusting the hole position, and driving the upper steel casing into the pile hole. The drilling rod must be vertical before drilling.

[0123] Drilling the upper pile hole: drilling into the karst cave to determine the position of the pile hole on the cave floor. At the beginning, the drill bit just touches the ground, and the drilling speed is controlled to be slow. During normal drilling, the torque and pressure control are realized by using microcomputer servo principle to achieve the corresponding drilling speed in each stratum. After the drilling depth reaches the design requirement, the hole depth, diameter, center, and shape are checked, and the pile diameter and inclination are detected by using the ultrasonic hole detector.

[0124] Burying the lower steel casing: drilling to a certain depth at the bottom of the karst cave to form a pre-buried hole, driving the lower steel casing into the pre-buried hole, and connecting the lower steel casing with the upper steel casing.

[0125] Secondary drilling at the bottom of the karst cave: drilling in the direction of the lower steel casing to form two pile holes from the ground to the karst cave and the bottom of the karst cave. The diameter of the pile hole below the karst cave is equal to the diameter of the pile hole above the karst cave.

[0126] Using a rotary drilling machine to drill the pile hole, and stopping drilling when encountering a karst cave.

[0127] Based on the karst cave data obtained by advanced drilling and tube wave detection, combined with the position and size of the test pile at the karst cave and soil cave determined by cross-hole CT scanning, and the type of pile foundation, the shape and size of the isolation structure are optimized by finite element simulation calculation, and the 3D printing program is written.

[0128] In-hole exploration and positioning: lowering the imaging equipment or the scanning system of the 3D printing equipment into the hole to accurately position the karst cave opening position and shape, and adjusting the printing scheme if necessary.

[0129] 3D printing equipment lowering and positioning: lowering the 3D printing equipment to the predetermined position (inside the karst cave or the section that needs to be isolated in the pile hole). The robot accurately determines its attitude and position using the positioning system.

[0130] Based on the three-dimensional scanning data of the karst cave, a printing path that completely matches the shape of the cavity is generated, and the isolation body is printed. Specifically, it can be printed layer by layer in situ:

[0131] The printing head accumulates materials layer by layer inside the karst cave according to the preset path (G code generated based on the three-dimensional model);

[0132] The thickness of each layer (such as 20-30 mm) needs to be set according to the material performance and robot capability;

[0133] The printing path needs to be optimized to ensure that the structure is dense, has no cavities, and maximizes the contact area with the surrounding rock;

[0134] Monitor print quality in real time (e.g., via robotic sensors or in-hole cameras).

[0135] Furthermore, the technical solutions of the embodiments of this application also have the following technical details:

[0136] Curing (if required): Cement-based materials typically require a certain amount of time (several hours) for hydration curing to reach sufficient strength, which can be accelerated by optimizing the material formulation (rapid setting) or by external measures (such as hot air).

[0137] Quality inspection: After printing, in-hole imaging, acoustic wave detection, or core sampling (if location permits) can be performed to verify the integrity, density, and adhesion to the surrounding rock of the isolator.

[0138] After the isolation body reaches the required strength, continue drilling to the designed depth.

[0139] Hole cleaning stage: Pay special attention to removing any sediment that has fallen onto the surface of the separator. Ensure the surface of the separator is clean to facilitate bonding with the concrete.

[0140] The steel reinforcement cage system is as follows: A truck crane is erected near the pile hole opening, and the crane lifts the steel reinforcement cages. The individual steel reinforcement cages are connected to each other and hoisted into the pile hole as a whole. The steel reinforcement cages are then vertically lowered along the upper and lower steel casings. After the steel reinforcement cages are lowered to the bottom of the pile, the central axis of the steel reinforcement cages coincides with the centerline of the pile hole. The pre-reserved steel reinforcement of the isolation body is then spot-welded to the pile reinforcement cages.

[0141] Furthermore, a grouting pipe for injecting concrete slurry is placed inside the pile hole. The grouting outlet of the grouting pipe is located inside the reinforcing cage. During the grouting process inside the reinforcing cage, the isolator at the location of the karst cave integrates with the cast-in-place pile to form the pile foundation bearing structure at the karst cave location.

[0142] Concrete pouring: A guide pipe is installed inside the pile hole. After the guide pipe is installed, the sediment at the bottom of the hole is measured. When the sediment thickness meets the requirements, concrete is poured in batches until the concrete height reaches the ground. Concrete grout is injected into the pile hole through the grouting pipe. The concrete level rises to the karst cave and is blocked by the isolation structure, thus preventing concrete loss. At the same time, it forms an integral part with the isolation structure to form the pile foundation bearing structure at the karst cave. Concrete is poured to the top of the pile, and after the concrete grout solidifies and hardens, a cast-in-place pile is formed. When the concrete is poured to the upper steel casing, the upper steel casing is removed. After construction is completed, the pile formation effect is inspected. If the requirements are met, the next step of construction can be carried out.

[0143] Specifically, the isolation body forms a hollow tubular structure that conforms to the pile body (inner diameter = design pile diameter).

[0144] The isolation body in this embodiment of the application serves the following functions:

[0145] Isolation cavity: block the cave space to prevent mud, concrete, groundwater loss.

[0146] Stable hole wall: provide support to prevent hole wall collapse.

[0147] Uniform load transfer: as the transition layer between the pile body and the stable rock mass, effectively transfer the pile foundation load to the stable bearing layer.

[0148] Adapt to complex morphology: no need to precast mold, can perfectly fit various irregular cave shapes.

[0149] Specifically, there are pile holes in the soil layer, rock layer and cave, and the pile foundation is located inside the pile hole.

[0150] Specifically, the drilling equipment is a drilling machine, and the suspension device is a crane.

[0151] In a second aspect, the embodiments of the present application provide a construction method of the construction tool for drilling and pouring pile foundation in karst area based on the first aspect, which comprises the following steps:

[0152] S1, detecting the cave position of the target cave, and vertically driving a pre-set upper steel casing 1 from the ground corresponding to the cave position until the top of the target cave is penetrated;

[0153] S2, drilling through the area around the top of the target cave surrounded by the upper steel casing 1 to drill an upper pile hole, the upper pile hole penetrates the top of the target cave and remains vertical, and is directed towards the bottom of the target cave;

[0154] S3, drilling a hole bottom pre-buried hole at the area of the bottom of the target cave opposite to the upper pile hole, and driving a lower steel casing 2 with a pre-set size smaller than the upper steel casing 1 into the top of the target cave until the lower steel casing 2 is coaxially and spacedly arranged below the upper steel casing 1, and the area around the bottom of the target cave surrounded by the lower steel casing 2 is drilled through, and the bottom of the lower steel casing 2 is located inside the bottom of the target cave;

[0155] S4, arranging a 3D printing scanning head 3 and a 3D printing nozzle 4 in the target cave;

[0156] S5, controlling the 3D printing scanning head 3 to measure the internal structure of the target cave to obtain the internal topography of the target cave;

[0157] S6, based on the three-dimensional geological model, the positions of the upper steel casing 1 and the lower steel casing 2 in the target cave, and the internal topography of the target cave, obtaining the isolation body structure information

[0158] S7, based on the isolation body structure information, the 3D printing nozzle 4 constructs the isolation body A in the target cave;

[0159] S8, after the isolation body A is constructed, hoist the reinforcement cage B in the area surrounded by the upper steel casing 1, the lower steel casing 2 and the isolation body A, and pour the pile C; wherein,

[0160] The isolation body A is a cylindrical structure, which can be a circular cylindrical structure, the bottom of which starts from the connection between the lower steel casing 2 and the bottom of the target cave, and the top of which stops at the connection between the upper steel casing 1 and the top of the target cave, and the shape of the isolation body A is printed according to the actual morphology of the cave;

[0161] The outer wall of the upper steel casing 1 and the lower steel casing 2 is in contact with the inner wall of the isolation body A.

[0162] Specifically, in step S3, for the convenience of construction, the size of the lower steel casing 2 is made according to the hole diameter of the pile hole, and the size of the upper steel casing 1 is 1.1 times the size of the lower steel casing 2.

[0163] In step S7, based on the isolation body structure information, the 3D printing nozzle 4 constructs the isolation body A in the target cave, and during the printing process, the reserved tie steel bars are arranged at intervals along the height to be connected with the reinforcement cage.

[0164] The embodiments of the present application aim at the defects of conventional methods (such as grouting filling, casing following, backfilling stone clay, etc.), such as non-dense filling, poor shape adaptability, low efficiency, uncontrollable effect, especially poor effect on irregular caves, etc. The 3D printing technology is used to construct a high-strength isolation / support / anti-seepage structure body in situ, on demand and accurately, which fits the complex cave morphology, fills / isolates without dead angle, avoids overfilling, greatly reduces the risk of slurry leakage, hole collapse and concrete loss, effectively overcomes the limitations of traditional methods, significantly improves the safety, reliability and efficiency of pile forming, has small disturbance to the surrounding rock and soil, and can effectively handle caves with extremely irregular shape, special location (such as directly below the pile end) and large or strong connectivity.

[0165] It should be emphasized that the technical scheme of the embodiments of the present application is used for the construction of cast-in-place piles in karst development areas, and the pile pouring does not consume a large amount of concrete to fill the cave;

[0166] The technical scheme of the embodiment of the application is suitable for complex karst cave forms, avoids dead angle filling / isolation, avoids overfilling, greatly reduces the risk of slurry leakage, hole collapse and concrete loss, effectively overcomes the limitations of traditional methods, significantly improves the safety, reliability and efficiency of the pile, has small disturbance to the surrounding rock and soil, and can effectively handle extremely irregular forms, special positions (such as directly below the pile end), super-large or connected karst caves that are difficult to deal with by traditional methods;

[0167] By integral pouring of the isolation body and the pile body, the pile body is better and more closely engaged with the bedrock in the karst area to jointly bear, thereby improving the pile forming quality and single pile bearing capacity of the construction bored pile in complex geology, and realizing the integration of isolation, support and anti-seepage.

[0168] Further, based on the isolation body structure information, the 3D printing nozzle 4 constructs the isolation body A in the target karst cave, including the following steps:

[0169] The 3D printing nozzle 4 starts to construct the isolation body A from the connection between the lower steel casing 2 and the bottom of the target karst cave;

[0170] When the top of the isolation body A is close to the bottom end of the upper steel casing 1, the upper steel casing 1 is lifted, and the 3D printing nozzle 4 continues to construct the isolation body A;

[0171] When the top of the isolation body A contacts the top of the target karst cave, the upper steel casing 1 is restored to the original position.

[0172] It should be noted that the positional relationship and distance between the upper steel casing 2 and the top of the target karst cave are determined according to the 3D printing scanning head 3, the upper steel casing 2 is lifted by a crane to be away from the top of the karst cave by a distance, and normal printing is ensured.

[0173] Further, the bottom of the steel reinforcement cage B is lower than the bottom of the target karst cave and is located in the lower steel casing 2.

[0174] It should be noted that the construction method of the rock karst area bored pile foundation construction tool mentioned in the embodiment of the application is similar to the rock karst area bored pile foundation construction tool mentioned in the first aspect in terms of technical principles, technical problems, technical solutions and technical effects, and will not be repeated here.

[0175] In the description of the present application, it should be noted that the terms "upper", "lower", and the like are used for indicating the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0176] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0177] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A construction tool for bored pile foundations in karst areas, characterized in that, The construction equipment includes: An upper steel casing (1) extending from the ground of the area where the target cave is located into the top of the target cave; The lower steel casing (2) passes through the bottom of the target cave from the inside of the target cave, and the lower steel casing (2) is coaxially spaced below the upper steel casing (1); A top support (5) for the casing is set on the ground in the area where the target cave is located and is located on top of the upper steel casing (1); The bottom annular track (6) of the upper steel casing (1) is set on the inner wall of the bottom of the casing. The bottom slider (7) of the casing is slidably set on the annular track (6) at the bottom of the casing; A retractable scanning bracket (8) is provided at the bottom of the slider (7) at the bottom of the protective sleeve; The scanning base (9) is located at the bottom of the retractable scanning bracket (8); The 3D printing scanning head (3) and the 3D printing nozzle (4) are disposed on the side of the scanning base (9) opposite to the central axis of the upper steel casing (1); The 3D printing supply pipeline (10) extends from the top support (5) of the protective cylinder into the upper steel protective cylinder (1), passes through the bottom slider (7) of the protective cylinder and the retractable scanning bracket (8) in sequence, and finally into the scanning base (9). The 3D printing communication pipeline (11) built into the 3D printing supply pipeline (10) is connected to the 3D printing scanning head (3) and the 3D printing nozzle (4) at one end located in the target cave. The 3D printing material supply pipeline (12) built into the 3D printing supply pipeline (10) is connected to the 3D printing nozzle (4) at one end located in the target cave. The 3D printing control terminal (13) is connected to the ground end of the 3D printing communication pipeline (11) located in the area where the target cave is located, the bottom slider (7) of the protective cylinder, and the retractable scanning bracket (8). The 3D printing feed end (14) is connected to the ground end of the 3D printing feed pipeline (12) located in the area where the target cave is located, and is also connected to the 3D printing control end (13) via signal.

2. The drilling and grouting pile foundation construction equipment in karst areas as described in claim 1, characterized in that: The 3D-printed communication conduit (11) is a flexible cable.

3. The drilling and grouting pile foundation construction tooling in karst areas as described in claim 1, characterized in that: The 3D printing feed pipe (12) is a telescopic pipe.

4. The drilling and grouting pile foundation construction tooling in karst areas as described in claim 1, characterized in that: The cross-section of the annular track (6) at the bottom of the casing is I-shaped.

5. The drilling and grouting pile foundation construction tooling in karst areas as described in claim 1, characterized in that: The bottom annular track (6) of the casing is set on the bottom inner wall of the upper steel casing (1) by a number of symmetrically distributed bolts.

6. A construction method based on the drilling and grouting pile foundation construction equipment in karst areas as described in claims 1-5, characterized in that, The method includes the following steps: The location of the target cave is detected, and a pre-set upper steel casing (1) is driven vertically into the ground corresponding to the location of the cave until it passes through the top of the target cave; the area of ​​the top of the target cave surrounded by the upper steel casing (1) is drilled through. A lower steel casing (2), with a preset size smaller than the upper steel casing (1), is driven into the top of the target cave until the lower steel casing (2) is coaxially spaced directly below the upper steel casing (1), and the area around the bottom of the target cave surrounded by the lower steel casing (22) is drilled through, with the bottom of the lower steel casing (2) located inside the bottom of the target cave. A 3D printing scanning head (3) and a 3D printing nozzle (4) are installed inside the target cave. The 3D printing scanning head (3) is controlled to measure the internal structure of the target cave and obtain the internal morphology of the target cave. Based on the three-dimensional geological model, the orientation of the upper steel casing (1) and the lower steel casing (2) within the target cave, and the internal morphology of the target cave, the structural information of the isolation body is obtained; Based on the structure information of the isolator, the 3D printing nozzle (4) constructs an isolator (A) within the target karst cave; After the isolation body (A) is constructed, a reinforcing cage (B) is hoisted into the area surrounded by the upper steel casing (1), the lower steel casing (2), and the isolation body (A), and the cast-in-place piles (C) are poured; wherein, The isolation body (A) is a cylindrical structure, with its bottom starting at the connection between the lower steel casing (2) and the bottom of the target cave, and its top ending at the connection between the upper steel casing (1) and the top of the target cave. The outer walls of the upper steel casing (1) and the lower steel casing (2) are in contact with the inner wall of the isolation body (A).

7. The construction method of the drilling and grouting pile foundation construction equipment in karst areas as described in claim 6, characterized in that, Based on the isolation structure information, the 3D printing nozzle (4) constructs an isolation body (A) within the target karst cave, including the following steps: The 3D printing nozzle (4) begins to construct the isolation body (A) from the connection between the lower steel casing (2) and the bottom of the target cave. When the top of the isolator (A) is close to the bottom of the upper steel casing (1), the upper steel casing (1) is lifted up, and the 3D printing nozzle (4) continues to build the isolator (A); When the top of the isolation body (A) comes into contact with the top of the target cave, the upper steel casing (1) is restored to its original position.

8. The construction method of the drilling and grouting pile foundation construction equipment in karst areas as described in claim 6, characterized in that: The bottom of the steel cage (B) is lower than the bottom of the target karst cave and is located inside the lower steel casing (2).

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