Visual testing method and system for failure and damage characteristics of tubular pile penetrating through double-layer karst cave

Abstract

The invention provides a visual testing method and system for failure damage characteristics of a tubular pile penetrating through a double-layer karst cave, and the method comprises the steps: firstly obtaining a rock stratum type of a target karst area and target karst cave data, then configuring simulation concrete, and then employing 3D printing equipment for printing to obtain a karst cave simulation entity. And after the karst cave simulation entity is pre-fixed, the simulation concrete is put into the model box and watered for maintenance. And after the simulation concrete is solidified, the template is removed, the karst cave simulation entity is taken out, and a simulation model is formed. Then, a hole is formed in the top of the simulation model, the formwork is installed back, grouting is conducted in the hole formed in the top of the simulation model, and a model pile is placed in the hole formed position; and after grouting around the model pile is solidified, a counter-force frame is arranged, a rock-soil layer around the model pile is monitored through a PIV image processing system, and settlement simulation data and static load data are obtained. And finally, if the settlement simulation data is lower than the settlement threshold value and the static load data is larger than the static load lower limit, notices of field drilling, pile foundation insertion and grouting are sent to the target karst area.

Description

Technical Field

[0001] The invention belongs to the technical field of pile foundation engineering, and in particular relates to a method and system for visualizing failure and damage characteristics of a pipe pile passing through a double-layer karst cave. Background Art

[0002] Karst geology is a common adverse geological phenomenon in the engineering field. Bridges, roads and construction projects built on karst geology are prone to settlement or collapse. In order to deal with the above problems, "pile foundations" are set up in karst geology in the engineering field. With its excellent bearing capacity and low settlement characteristics, "pile foundations" show unique advantages in crossing caves and penetrating into rock strata, and have become an important support for engineering construction in karst areas. However, the construction of large-diameter rock-embedded piles in karst areas has always been a major problem in the field of engineering technology. Ideally, pile foundation design should avoid cave formations, but the complex and changeable karst geological conditions often make this strategy difficult to fully implement, and initial exploration methods such as drilling are difficult to fully reveal the distribution of caves. In areas with dense caves, pile foundations cannot completely avoid underground caves.

[0003] Therefore, how to pre-test whether pile foundations can be constructed in the target karst area without avoiding caves has become a technical problem that urgently needs to be overcome in the current construction of buildings, bridges and roads. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method and system for visualizing the failure characteristics of a pipe pile passing through a double-layer cave, which are used to solve the problems existing in the prior art.

[0005] In a first aspect, in order to achieve the above-mentioned purpose, the present invention provides a method for visualizing the failure characteristics of a pipe pile passing through a double-layer cave, comprising:

[0006] S10: Obtaining rock formation type and target cave data in the target karst area;

[0007] Among them, the underground of the target karst area has double-layered caves with upper and lower layers;

[0008] S20: Configure simulated concrete according to the rock formation type;

[0009] S30: using a 3D printing device to print a simulated cave entity according to the target cave data;

[0010] S40: After the karst cave simulation entity is pre-fixed to the preset model box, the simulation concrete is put into the model box and watered for curing;

[0011] S50: After the simulated concrete solidifies, the front template of the model box is removed, and the simulated entity of the cave is taken out to form a simulation model;

[0012] S60: opening a hole toward the top of the simulation model;

[0013] S70: After the front template of the model box is installed back, grouting is performed toward the top opening of the simulation model, and prefabricated model piles are placed along the opening position;

[0014] S80: After the grouting around the model pile solidifies, a reaction frame is set for the model pile, and a PIV image processing system is used to monitor the rock and soil layer around the model pile to obtain settlement simulation data and static load data;

[0015] S90: If the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit, a notice of field drilling, pile foundation insertion and grouting is issued to the target karst area.

[0016] Through the above technical solution, in order to test whether the target karst area can be built with karst pile foundation, the method of the present invention adopts an equivalent model replacement simulation method for verification, and performs visual monitoring through the PIV image processing system. Compared with the prior art, the method of the present invention can test whether the target karst area can be built with karst pile foundation in a more intuitive, low-cost and high-simulation manner.

[0017] Preferably, after S50, the method of the present invention further comprises:

[0018] S500: Obtaining the type of soil covering layer and configuring simulated soil covering;

[0019] S501: Covering the top surface of the simulation model with simulated soil.

[0020] Preferably, if the type of the covering soil layer is weathered soil, the components of the simulated covering soil at least include quartz sand, clay, lubricating oil and water.

[0021] Preferably, the mass proportion of the components of the simulated covering soil is: quartz sand: clay: lubricating oil: water = 1: 0.75-0.85: 0.01-0.03: 0.25-0.35.

[0022] Preferably, if the rock layer type is a slightly weathered limestone layer, the components of the simulated concrete include at least dry river sand, silicate cement, plaster of Paris and light calcium carbonate.

[0023] Preferably, the water-cement ratio of the simulated concrete is 0.25-0.35; the mass proportion of the components of the simulated concrete is: dry river sand: Portland cement: plaster of Paris: light calcium carbonate = 1: 0.24-0.28: 0.24-0.28: 0.02-0.06.

[0024] Preferably, the reaction frame includes a base, a reaction column and a reaction beam, the reaction column is vertically arranged and fixedly connected to the base, and both ends of the reaction beam are respectively fixedly connected to two reaction columns spaced apart from each other. In S80, the reaction frame is specifically arranged for the model pile as follows:

[0025] S81: placing the model box on the base;

[0026] S82: Take a jack, set the lower base of the jack on the top of the model pile, and make the upper joint of the jack contact the reaction beam;

[0027] S83: Use a jack to apply pressure to the top of the model pile.

[0028] Preferably, the PIV image processing system includes at least a first vertical displacement sensor, a load sensor, a PIV image processing camera and an on-site construction control terminal; the model box is made of a transparent material; after setting a reaction frame for the model pile in S80, the method of the present invention further includes:

[0029] S84: a load sensor is arranged between the jack and the model pile;

[0030] S85: installing a first vertical displacement sensor in the cave groove of the simulation model;

[0031] S86: Align the PIV image processing camera lens to the front of the model box;

[0032] S87: Using the on-site construction control terminal, the static load data monitored by the load sensor, the settlement simulation data monitored by the first vertical displacement sensor, and the model pile image taken by the PIV image processing camera are obtained.

[0033] Preferably, after S30, the method of the present invention further comprises:

[0034] S300: making model piles based on the spatial dimensions of the karst cave simulation entity;

[0035] The model pile is hollow; the outer diameter of the model pile is smaller than the width of the simulated entity of the cave;

[0036] S301: grinding the outer surface of the model pile with sandpaper;

[0037] S302: Strain gauges are arranged at the top, middle and bottom of the inner cavity of the model pile;

[0038] The strain gauge is communicatively connected to the PIV image processing system.

[0039] Preferably, after S60,

[0040] Drill 40mm-50mm deep into the bottom of the lower cave of the simulation model.

[0041] In a second aspect, the present invention further provides a visualization test system for failure characteristics of a pipe pile passing through a double-layer cave, using the visualization test method for failure characteristics of a pipe pile passing through a double-layer cave, the system comprising:

[0042] A data acquisition module, used to acquire the rock formation type and target cave data of the target karst area;

[0043] Concrete configuration equipment, used to configure simulated concrete according to rock formation type;

[0044] 3D printing equipment, used to print out a simulated cave entity according to the target cave data;

[0045] Concrete placing equipment is used to place the simulated concrete into the model box and water it for curing after the simulated cave entity is pre-fixed to the preset model box;

[0046] Construct a withdrawal device, which is used to remove the front template of the model box after the simulated concrete solidifies, take out the karst cave simulation entity, and form a simulation model;

[0047] A hole-making device, used for making a hole toward the top of the simulation model;

[0048] The model pile placement device is used to install the front template of the model box back, inject grout towards the top opening of the simulation model, and place the prefabricated model pile along the opening position;

[0049] The reaction force assembly equipment is used to set the reaction force frame on the model pile after the peripheral grouting of the model pile solidifies;

[0050] PIV image processing system, used to monitor the rock and soil layers around the model piles and obtain settlement simulation data and static load data;

[0051] The on-site construction control terminal is used to issue a notification of on-site drilling, pile foundation insertion and grouting to the target karst area if the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit.

[0052] The present invention has at least the following advantages:

[0053] 1) Compared with the prior art, the method of the present invention can test whether the target karst area can be constructed with karst pile foundation in a more intuitive, low-cost and high-simulation manner.

[0054] 2) Compared with the prior art, the method of the present invention specially develops a simulated concrete of slightly weathered limestone layer, and after solidification, the structural characteristics and mechanical properties of the simulated concrete are more similar to those of slightly weathered limestone layer.

[0055] 3) Compared with the prior art, the PIV image processing system in the system of the present invention is linked with the on-site construction control terminal, which can quickly transmit laboratory results to the site, thereby improving the efficiency of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 The present invention is a flowchart of a method for visualizing failure characteristics of a pipe pile passing through a double-layer cave in the first embodiment of the present invention.

[0058] Figure 2 It is a structural schematic diagram of a cave simulation entity of a method for visualizing failure characteristics of pipe piles passing through a double-layer cave in the first embodiment of the present invention.

[0059] Figure 3 Schematic diagram of the model pile structure of the method for visualizing the failure characteristics of pipe piles passing through a double-layer cave in the first embodiment of the present invention.

[0060] Figure 4 Schematic diagram of the internal structure of a model pile of a method for visualizing failure characteristics of a pipe pile passing through a double-layer cave in Example 1 of the present invention.

[0061] Figure 5 This is a diagram showing the effect of the failure and damage characteristics visualization test method of a pipe pile passing through a double-layer cave in the first embodiment of the present invention after S50 is executed.

[0062] Figure 6 This is a diagram showing the effect of the failure and damage characteristics visualization test method of a pipe pile passing through a double-layer cave in the first embodiment of the present invention after S60 is executed.

[0063] Figure 7 This is a diagram showing the effect of grouting in step S70 of the method for visualizing failure characteristics of pipe piles passing through double-layer caves in the first embodiment of the present invention.

[0064] Figure 8 This is a diagram showing the effect of the failure and damage characteristics visualization testing method of a pipe pile passing through a double-layer cave in the first embodiment of the present invention after step S80 is executed.

[0065] Fig. 9 It is a structural schematic diagram of the failure and damage characteristics visualization testing system of the pipe pile passing through the double-layer cave in the second embodiment of the present invention.

[0066] Figure numerals: 1. karst cave simulation entity; 2. model pile; 21. groove; 3. strain gauge; 4. transparent concrete; 5. model box; 6. simulation model; 7. handheld coring drill; 71. main engine handle; 72. extended joystick; 73. diamond drill bit; 8. high-pressure double-liquid grouting machine; 81. adjustment switch; 82. first seismic pressure gauge; 83. second seismic pressure gauge; 84. control valve; 9. cone; 100. base; 101. reaction column; 102. reaction beam; 103. jack; 200. cross bar; 201. vertical bar; 300. covering soil layer; 400. steel block; 900. PIV image processing camera; 901. on-site construction control terminal; 902. load sensor; 903. acoustic emission sensor; 904. first vertical displacement sensor; 905. second vertical displacement sensor; 906. infrared displacement sensor. DETAILED DESCRIPTION

[0067] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred system or element must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0069] This embodiment discloses a method and system for visualizing the failure characteristics of a pipe pile passing through a double-layer cave, which are used to solve the problems existing in the prior art.

[0070] Embodiment 1

[0071] like Figure 1 As shown, this embodiment discloses a method for visualizing failure characteristics of a pipe pile passing through a double-layer cave, including:

[0072] S10: Obtain rock formation type and target cave data in the target karst area.

[0073] In this embodiment, the target karst area refers to the construction site, and its rock layer type can be obtained by using conventional geological drilling methods to obtain soil samples, and using instrument determination or solvent extraction methods to analyze its rock layer type. The target cave data can be obtained using an elastic wave cave detector, and the target cave data includes the number, volume and size of the caves.

[0074] It should be noted that the target karst area of ​​this embodiment has double-layer caves with upper and lower layers underground.

[0075] S20: Configure simulated concrete according to the rock formation type.

[0076] If the rock layer type is a slightly weathered limestone layer, the components of the simulated concrete at least include dry river sand, silicate cement, plaster of Paris and light calcium carbonate.

[0077] It should be explained that the compressive strength of slightly weathered limestone is mostly 80-100MPa, the elastic modulus is 5000-6000Mpa, the cohesion is mostly 13-15MPa, the internal friction angle is generally 30-50°, and the density is 2.0-2.8 / g·cm -1 between.

[0078] According to the physical properties of the slightly weathered limestone mentioned above, taking into account the purpose of the model experiment, the scalable size of the cave, the diameter of the model pile in real life, the size of the model box in an ordinary laboratory and other conditions, the geometric similarity ratio is set to 18, the bulk density similarity ratio is set to 1.2, and the stress similarity ratio can be calculated to be 21.6. Therefore, the target value of the compressive strength of the simulated concrete after solidification should be 3.70-4.63MPa, the target value of the elastic modulus should be 230-280Mpa, the target value of the cohesion should be 0.60-0.69MPa, the target value of the internal friction angle should be 30-50°, and the target value of the density should be 1.67-2.33 / g·cm 3 between.

[0079] Furthermore, in order to achieve the above-mentioned physical property index after proportional reduction, this embodiment provides a simulated concrete. Specifically, the water-cement ratio of the simulated concrete is 0.3; the mass proportion of the components of the simulated concrete is: dry river sand: silicate cement: plaster of Paris: light calcium carbonate = 1: 0.26: 0.26: 0.04.

[0080] In this embodiment, the silicate cement is 425 ordinary silicate cement. After multiple tests, the compressive strength of the simulated concrete after solidification is 4.14MPa, the elastic modulus is 252.69MPa, the cohesion is 0.65MPa, the internal friction angle is 46.7°, and the density is 1.94g / cm 3 .

[0081] S30: Using 3D printing equipment, according to the target cave data, print out a cave simulation entity.

[0082] Among them, before S30, it is necessary to design the size of the cave simulation entity and the model box according to the similarity ratio of the geometric dimensions.

[0083] like Figure 2 As shown, according to the target cave data, the printing data of the cave simulation entity 1 is obtained by adopting the similarity ratio scaling method, and then the printing data is placed in the 3D printing device to print out the cave simulation entity 1.

[0084] After S30, the method of the present invention further includes:

[0085] S300: making a model pile 2 based on the spatial dimensions of the cave simulation entity 1;

[0086] The model pile 2 is hollow; the outer diameter of the model pile 2 is smaller than the width of the cave simulation entity 1;

[0087] S301: grinding the outer surface of the model pile 2 with sandpaper;

[0088] S302: Strain gauges 3 are arranged at the top, middle and bottom of the inner cavity of the model pile 2;

[0089] The strain gauge 3 is communicatively connected to the PIV image processing system.

[0090] More specifically, Figure 3 and Figure 4 As shown, the model pile 2 is made of acrylic. In order to enhance the pile-slurry bonding strength, a groove 21 is set at a certain distance on the outside of the customized model pile 2. The surface of the model pile 2 made of acrylic material is smooth and the side friction resistance is small, which does not conform to the actual situation. It is necessary to first grind the outer surface of the pile body with sandpaper to increase the roughness, and then use sand with a particle size of 1.3-1.6mm and epoxy resin glue to treat the surface of the foundation pile. Apply epoxy resin glue on the surface of the model pile 2, and use a soft brush to quickly make the thickness uniform, then sprinkle sand evenly on the epoxy resin, press the sand with the back of the brush, so that half of the sand is in the glue and half is exposed to the air. The sand cannot overlap to prevent uneven thickness on the pile surface. Finally, the strain gauge 3 is attached to the upper, middle and lower positions of the inner cavity of the model pile 2 corresponding to the karst cave. Before attaching the strain gauge 3, the surface of the patch is polished with coarse and fine sandpaper in turn. Then use cotton dipped in alcohol to wipe the model pile 2 clean and accurately mark the patch position of the strain gauge 3. Drip an appropriate amount of 502 glue onto the patch, place the strain gauge 3, cover it with a polyethylene film, press and roll the strain gauge 3 with your fingers to squeeze out the excess glue and bubbles, press for 30 seconds, and after the glue hardens, carefully tear off the film, and the strain gauge 3 is pasted. After pasting, use 703 silicone rubber to cover the surface of the strain gauge 3, which can effectively absorb vibration and impact, and has good barrier properties against water and moisture. Finally, in order to facilitate the subsequent PIV image processing system to monitor the deformation of the pile, it is necessary to fill the inner cavity of the model pile 2 with transparent concrete 4.

[0091] S40: After the karst cave simulation entity 1 is pre-fixed to the preset model box 5, the simulation concrete is put into the model box 5 and watered for curing.

[0092] In this embodiment, the model box 5 is made of transparent material.

[0093] S50: After the simulated concrete solidifies, remove the front template of the model box 5, take out the karst cave simulation entity 1, and form a simulation model 6.

[0094] Furthermore, the above S40-S50 are specifically:

[0095] like Figure 5 As shown, in order to overcome the influence of buoyancy on the karst cave in concrete during pouring, the karst cave simulation entity 1 is firmly fixed to the designated position of the front template of the model box 5 with 502 glue. The above-mentioned simulation concrete is evenly mixed with a drum mixer and poured into the model box 5. The concrete in the model box 5 is vibrated and compacted with a handheld concrete vibrator to discharge bubbles. After the above-mentioned simulation concrete is finally set, the front template is removed to take out the two semi-ellipsoidal karst caves. The test block is transferred to suitable conditions and watered for 30 days. At this time, the double-layer karst cave simulation model 6 is cast.

[0096] Preferably, after the above S50, the method of the present invention further comprises:

[0097] S500: Obtain the type of the covering soil layer 300 and configure the simulated covering soil;

[0098] S501: Covering the top surface of the simulation model 6 with simulated covering soil.

[0099] If the type of the covering soil layer 300 is weathered soil, the components of the simulated covering soil at least include quartz sand, clay, lubricating oil and water.

[0100] Furthermore, the mass proportion of the components of the simulated covering soil is: quartz sand: clay: lubricating oil: water = 1: 0.81: 0.02: 0.30.

[0101] The direct shear test showed that the cohesion of the simulated cover soil after compaction was 12.70 kPa, and the internal friction angle was 32.33°, which can better reflect the physical properties of the actual soil layer.

[0102] After S50, the method of the present invention further includes:

[0103] S60: A hole is opened toward the top of the simulation model 6.

[0104] Specifically, Figure 6 As shown, a semi-cylindrical rough hole is drilled above the simulation model 6 using a handheld coring drill 7, and the hole penetrates the double-layer cave to facilitate subsequent grouting in the hole. The rough hole is conducive to enhancing the slurry-soil bonding force.

[0105] In this embodiment, the handheld coring drill 7 is mainly composed of a main machine handle 71 , an extended joystick 72 and a diamond drill bit 73 .

[0106] S70; after the front template of the model box 5 is installed back, grouting is performed toward the top opening of the simulation model 6, and the prefabricated model pile 2 is placed along the opening position.

[0107] like Figure 7 As shown, the front template of the model box 5 is reinstalled to prevent the A and B grouting liquids from leaking out from the front of the cave when the A and B grouting liquids are subsequently injected.

[0108] In this embodiment, a high-pressure double-liquid grouting machine 8 is used to inject grouting liquids A and B into the cave from the hole. After the liquids A and B solidify quickly, the template is removed and a frustum 9 is formed in the cave. The double-liquid grouting machine controls the pressure by adjusting the switch 81, and has multiple pressure levels for adjustment. Figure 7 In the embodiment, the first seismic pressure gauge 82 is a seismic pressure gauge for the high pressure pipe of grouting liquid A and grouting liquid B, and the second seismic pressure gauge 83 is a seismic pressure gauge for the mixed high pressure pipe of grouting liquid A and grouting liquid B. In this embodiment, the pressure value in the high pressure pipe is monitored in real time by the pressure gauge. Figure 7 In the embodiment, the output pipeline of the high pressure double liquid grouting machine 8 is provided with a control valve 84. In the present embodiment, the function of the frustum 9 is to prevent the simulation model 6 from leaking during the subsequent pile side grouting.

[0109] Preferably, after the cone 9 is solidified, the handheld coring drill 7 is used again to continue drilling a semi-cylindrical rough hole on the cone 9 in the cave. This time, in addition to penetrating the double-layer cave, it is necessary to continue drilling down 45 mm in the lower cave, that is, to drill into the rock layer, to facilitate the subsequent embedding of the end of the model pile 2.

[0110] After S70 , the simulation model 6 needs to be covered with simulated covering soil and compacted.

[0111] S80: After the grouting around the model pile 2 solidifies, a reaction frame is set for the model pile 2, and a PIV image processing system is used to monitor the rock and soil layer around the model pile 2 to obtain settlement simulation data and static load data.

[0112] The step of setting the reaction frame for the model pile 2 in S80 is as follows:

[0113] S81: placing the model box 5 on the base 100;

[0114] S82: Take the jack 103, set the lower base 100 of the jack 103 on the top of the model pile 2, and make the upper joint of the jack 103 contact the reaction beam 102;

[0115] S83: Apply pressure to the top of the model pile 2 using the jack 103 .

[0116] Furthermore, after setting the reaction frame for the model pile 2 in S80, the method of the present invention further includes:

[0117] S84: a load sensor 902 is arranged between the jack 103 and the model pile 2;

[0118] S85: installing a first vertical displacement sensor 904 in the cave of the simulation model 6;

[0119] S86: Align the lens of the PIV image processing camera 900 to the front of the model box 5;

[0120] S87: Using the on-site construction control terminal 901 to obtain the static load data monitored by the load sensor 902 , the settlement simulation data monitored by the first vertical displacement sensor 904 , and the image of the model pile 2 taken by the PIV image processing camera 900 .

[0121] Specifically, Figure 8 and Fig. 9 As shown, the simulation model 6 and the model pile 2 are transferred to the reaction frame for static load. In this embodiment, the reaction frame is composed of a steel plate base 100, a reaction column 101, a reaction beam 102 and a jack 103, and the PIV image processing system includes a PIV image processing camera 900, an on-site construction control terminal 901, a load sensor 902, an acoustic emission sensor 903, a first vertical displacement sensor 904, a second vertical displacement sensor 905 and an infrared displacement sensor 906.

[0122] Furthermore, the load sensor 902 is fixed to the lower base 100 of the jack 103 by bolts. Six acoustic emission sensors 903 are arranged on the front of the simulation model 6 to monitor the cracks of the simulation model 6 when it is subjected to static load. Then, a transparent glass plate is customized with the same size as the front template of the model box 5. Since the bedrock itself cannot fit tightly with the transparent glass plate after contact, a layer of vaseline is brushed on the surface of the transparent glass plate to make the two contact tightly. In addition, in order not to affect the subsequent PIV image processing camera 900 to monitor the deformation of the rock and soil layer, it is also necessary to wipe with a paper towel until the vaseline does not affect the transmittance. Six vertical displacement sensors are evenly arranged in the upper and lower caves in the simulation model 6 to measure the deformation of the top plate of the simulation model 6.

[0123] In this embodiment, a cross bar 200 is used to connect the bottom end of the vertical displacement sensor. At the same time, a hole is opened on the transparent glass plate at the position corresponding to the cross bar 200, and the cross bar 200 is fixed on the glass. In order to make the cross bar 200 more stable, the cross bar 200 is fixed on the steel plate base 100 by a vertical rod 201 after passing through the simulation model 6.

[0124] In this embodiment, six vertical displacement sensors are used to monitor the deformation of the soil sample, that is, to monitor the static load data. The infrared displacement sensor 906 arranged on the model pile 2 is used to measure the settlement of the pile top, that is, to monitor the settlement simulation data. Among them, because the jack 103 applies pressure to the pile top during static load, the infrared displacement sensor 906 cannot directly irradiate the pile top, so a steel block 400 is placed on the pile top, and the settlement of the pile top of the model pile 2 is equivalently represented by measuring the settlement of the steel block 400.

[0125] After the above simulation steps S10-S70 are completed, a PIV image processing camera 900 is set up on the front of the simulation model 6, and the deformation of the test block can be dynamically analyzed through this camera. In this embodiment, the vertical displacement sensor, strain gauge 3, force sensor, acoustic emission sensor 903 and infrared displacement sensor 906 are all connected to a preset data acquisition instrument, and then connected to a computer (on-site construction control terminal 901) through the data acquisition instrument communication. Then the static load test is started. After the static load reaches the termination condition, the volume and area of ​​the shear body generated by the top plate shearing failure and the shear body generated by the pile bottom shearing failure need to be quantitatively characterized, and the boundary of the failure body is scanned by the infrared displacement sensor 906 to obtain settlement simulation data and static load data.

[0126] S90: If the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit, a notice of field drilling, pile foundation insertion and grouting is issued to the target karst area.

[0127] Through the above technical solutions S10-S90, in order to test whether the target karst area can be built with karst pile foundation, the method of the present invention adopts an equivalent model replacement simulation method for verification, and performs visual monitoring through the PIV image processing system. Compared with the prior art, the method of the present invention can test whether the target karst area can be built with karst pile foundation in a more intuitive, low-cost and high-simulation manner.

[0128] Embodiment 2

[0129] This embodiment discloses a visualization test system for failure characteristics of pipe piles passing through double-layer caves, which adopts the visualization test method for failure characteristics of pipe piles passing through double-layer caves described in the first embodiment. The system includes:

[0130] A data acquisition module, used to acquire the rock formation type and target cave data of the target karst area;

[0131] Concrete configuration equipment, used to configure simulated concrete according to rock formation type;

[0132] 3D printing equipment, used to print out a simulated cave entity according to the target cave data;

[0133] Concrete placing equipment is used to place the simulated concrete into the model box and water it for curing after the simulated cave entity is pre-fixed to the preset model box;

[0134] Construct a withdrawal device, which is used to remove the front template of the model box after the simulated concrete solidifies, take out the karst cave simulation entity, and form a simulation model;

[0135] A hole-making device, used for making a hole toward the top of the simulation model;

[0136] The model pile placement device is used to install the front template of the model box back, inject grout towards the top opening of the simulation model, and place the prefabricated model pile along the opening position;

[0137] The reaction force assembly equipment is used to set the reaction force frame on the model pile after the peripheral grouting of the model pile solidifies;

[0138] PIV image processing system, used to monitor the rock and soil layers around the model piles and obtain settlement simulation data and static load data;

[0139] The on-site construction control terminal is used to issue a notification of on-site drilling, pile foundation insertion and grouting to the target karst area if the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit.

[0140] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above-mentioned method embodiment; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk, etc. Various media that can store program codes.

[0141] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for visualizing the failure characteristics of a pipe pile passing through a double-layer cave, characterized in that: include: S10: Obtaining rock formation type and target cave data in the target karst area; Wherein, the underground of the target karst area is distributed with double-layered caves in upper and lower layers; S20: configuring simulated concrete according to the rock formation type; S30: using a 3D printing device to print a simulated cave entity (1) according to the target cave data; S40: After the karst cave simulation entity (1) is pre-fixed to a preset model box (5), the simulation concrete is put into the model box (5) and watered for curing; S50: After the simulated concrete solidifies, the front template of the model box (5) is removed, and the simulated cave entity (1) is taken out to form a simulated model (6); S60: opening a hole toward the top of the simulation model (6); S70; after the front template of the model box (5) is reinstalled, grouting is performed toward the top opening of the simulation model (6), and a prefabricated model pile (2) is placed along the opening; S80: After the grouting around the model pile (2) solidifies, a reaction frame is set for the model pile (2), and a PIV image processing system is used to monitor the rock and soil layer around the model pile (2) to obtain settlement simulation data and static load data; S90: If the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit, a notice of field drilling, inserting pile foundation and grouting is issued to the target karst area.

2. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 1 is characterized in that: After S50, the method further includes: S500: Obtain the type of the covering soil layer (300) and configure the simulated covering soil; S501: Covering the simulated covering soil on the top surface of the simulation model (6).

3. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 2 is characterized in that: If the type of the covering soil layer (300) is weathered soil, the components of the simulated covering soil at least include quartz sand, clay, lubricating oil and water; the mass proportion of the components of the simulated covering soil is: quartz sand: clay: lubricating oil: water = 1: 0.75-0.85: 0.01-0.03: 0.25-0.

35.

4. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 1 is characterized in that: If the rock layer type is a slightly weathered limestone layer, the components of the simulated concrete include at least dry river sand, silicate cement, plaster of Paris and light calcium carbonate; the water-cement ratio of the simulated concrete is 0.25-0.35; the mass mix ratio of the components of the simulated concrete is: dry river sand: silicate cement: plaster of Paris: light calcium carbonate = 1: 0.24-0.28: 0.24-0.28: 0.02-0.

06.

5. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 1 is characterized in that: The reaction frame comprises a base (100), a reaction column (101) and a reaction beam (102), wherein the reaction column (101) is vertically arranged and fixedly connected to the base (100), and the two ends of the reaction beam (102) are respectively fixedly connected to two reaction columns (101) spaced apart from each other. The step S80 of arranging the reaction frame for the model pile (2) specifically comprises: S81: placing the model box (5) on the base (100); S82: Take a jack (103), place the lower base of the jack (103) on the top of the model pile (2), and make the upper joint of the jack (103) abut against the reaction beam (102); S83: Using a jack (103) to apply pressure to the top of the model pile (2).

6. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 5 is characterized in that: The PIV image processing system comprises at least a first vertical displacement sensor (904), a load sensor (902), a PIV image processing camera (900) and an on-site construction control terminal (901); the model box (5) is made of a transparent material; after the reaction frame is provided for the model pile (2) in S80, the method further comprises: S84: Arranging the load sensor (902) between the jack (103) and the model pile (2); S85: installing the first vertical displacement sensor (904) in the cave groove of the simulation model (6); S86: Align the lens of the PIV image processing camera (900) with the front side of the model box (5); S87: Using the on-site construction control terminal (901) to obtain static load data monitored by the load sensor (902), settlement simulation data monitored by the first vertical displacement sensor (904), and the model pile image taken by the PIV image processing camera (900).

7. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 1 is characterized in that: After S30, the method further includes: S300: manufacturing the model pile (2) based on the spatial dimensions of the cave simulation entity (1); The model pile (2) is hollow; the outer diameter of the model pile (2) is smaller than the width of the karst cave simulation entity (1); S301: grinding the outer surface of the model pile (2) using sandpaper; S302: Strain gauges (3) are arranged at the top, middle and bottom of the inner cavity of the model pile (2); Wherein, the strain gauge (3) is communicatively connected to the PIV image processing system.

8. The method for visualizing failure characteristics of pipe piles passing through double-layer caves according to claim 1 is characterized in that: After the S60, Drill 40 mm to 50 mm deep into the bottom of the lower cave of the simulation model (6).

9. A visualization test system for failure characteristics of pipe piles passing through double-layer caves, characterized in that: The method for visualizing failure characteristics of a pipe pile passing through a double-layer cave according to any one of claims 1 to 8 is adopted, and the system comprises: A data acquisition module, used to acquire the rock formation type and target cave data of the target karst area; Concrete configuration equipment, used for configuring simulated concrete according to the rock formation type; A 3D printing device, used for printing a simulated cave entity (1) according to the target cave data; Concrete placing equipment, used for placing the simulated concrete into the model box (5) and watering and curing after the karst cave simulation entity (1) is pre-fixed to the preset model box (5); A withdrawal device is constructed to remove the front template of the model box (5) after the simulated concrete solidifies, and to take out the karst cave simulation entity (1) to form a simulation model (6); A hole-opening device, used for opening a hole toward the top of the simulation model (6); A model pile (2) placement device is used to install the front template of the model box (5), inject grout into the top opening of the simulation model (6), and place the prefabricated model pile (2) along the opening; A reaction force assembly device is used to set a reaction force frame on the model pile (2) after the grouting around the model pile (2) has solidified; A PIV image processing system is used to monitor the rock and soil layers around the model pile (2) to obtain settlement simulation data and static load data; The on-site construction control terminal (901) is used to send a notice of on-site drilling, inserting pile foundation and grouting to the target karst area if the settlement simulation data is lower than the settlement threshold and the static load data is greater than the static load lower limit.

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