Method for testing vertical bearing of foundation pile penetrating through karst cave in inclined stratified rock stratum

Abstract

The invention discloses a vertical bearing test method for a foundation pile penetrating through a karst cave in an inclined layered rock stratum, and belongs to the technical field of geotechnical engineering tests. The method focuses on manufacturing of a load test model for the inclined rock stratum penetrating through the karst cave foundation pile and is designed for a complex stratum with a non-horizontal rock stratum attitude. And the indoor test pile load test rock-like foundation is manufactured by splicing all layers of the inclined rock stratum. The preparation system comprises an inclined rock stratum, a karst cave and a karst cave penetrating test pile. The inclined rock stratum is prepared by using a specific mold according to a rock stratum inclination angle model. Silica gel is injected into the karst cave through a 3D printing mold, and a rock stratum is poured and formed; the test pile penetrating through the karst cave is formed through secondary pouring of the corresponding mold and the water leakage prevention glue. The detection system is composed of an optical fiber strain sensor and a soil pressure box. The invention provides a method for manufacturing a test model for researching a model load test of the cave-crossing foundation pile in the inclined stratified rock stratum, and assists in exploring the bearing deformation characteristic and mechanism of the cave-crossing foundation pile in the inclined stratified rock stratum.

Description

Technical Field

[0001] The present invention belongs to the field of geotechnical tests, and particularly relates to a method for vertical bearing test of a pile foundation passing through a karst cave in an inclined layered rock formation. Background Technique

[0002] In large-scale infrastructure construction, such as bridges, high-rise buildings, etc., pile foundations are often applied to complex geological conditions. When a pile passes through an inclined layered rock formation and contains a karst cave, its bearing performance and deformation characteristics are extremely complex. However, when a pile foundation passes through an inclined layered rock formation and there is a karst cave, its bearing performance and deformation characteristics become extremely complex. Traditional methods for vertical bearing tests of pile foundations are mostly aimed at horizontal strata or single geology, and it is difficult to simulate such complex situations. This makes it difficult for designers to master the bearing capacity and deformation law of pile foundations, bringing safety risks and economic waste to the project.

[0003] The inclined layered rock formation makes the distribution of the lateral friction resistance and end resistance of the pile foundation different from that of the horizontal strata, and factors such as the inclination angle of the rock formation and the interlayer bonding have a significant impact. The existence of a karst cave, due to its size, shape, position and relationship with the pile foundation, will cause problems such as stress concentration and uneven settlement of the pile foundation. Currently, for the research on such complex geology, there are deficiencies in the test models and methods. Existing models cannot accurately simulate the spatial relationship and interaction between the rock formation and the karst cave, and the test results are difficult to reflect the actual situation. Therefore, an effective test method is urgently needed to provide a reliable basis for the project. Summary of the Invention

[0004] The problem to be solved by the present invention is the deficiency and lack of the method for making inclined rock formations in existing indoor model test research. Therefore, a method for vertical bearing test of a pile foundation passing through a karst cave in an inclined layered rock formation is provided.

[0005] To solve the above problems, the present invention adopts the following technical solutions:

[0006] A method for vertical bearing test of a pile foundation passing through a karst cave in an inclined layered rock formation, characterized in that it includes: a box body, a rock formation dip angle model, karst cave preparation, a detection system, and a test pile passing through the karst cave; the box body is used to splice each layer of the inclined rock formation and finally form a structure similar to a rock foundation; the rock formation dip angle model is formed by designing a rock formation with a specific angle and pouring it with a single-layer template. The karst cave preparation is to print a karst cave - test pile mold by 3D printing, inject silicone, and then pour and form the rock formation; for the test pile passing through the karst cave, after completing the preliminary preparation, install the test pile synchronously when splicing the inclined rock formation, apply anti-leakage glue at the contact between the rock formation and the karst cave, and then perform secondary pouring of the remaining space; the detection system is composed of fiber optic strain sensors and earth pressure cells. During the preparation of the test pile, four grooves are reserved in advance for installing the fiber optic strain sensors; and when preparing the inclined rock formation, place the earth pressure cells at the reserved positions and then pour.

[0007] Preferably, the described box body is the basic framework structure of the entire test. Its size and material are designed and selected according to the test requirements to ensure that it can accommodate the assembled inclined rock stratum model and related test components, and has sufficient strength and stability to withstand various loads and operations during the test. The internal structure of the box body facilitates the assembly of the inclined rock stratum. Its edges and connection parts are treated with rivets and waterproof adhesives to ensure that no deformation or damage occurs during the rock stratum pouring and test process, thus affecting the accuracy of the test results.

[0008] Preferably, the forming process of the described karst cave preparation is as follows: First, 3D print the karst cave - test pile mold and customize the cutting to ensure that it can be matched with the rock stratum inclination model for pouring, and the inner diameter of the mold is slightly larger than the outer diameter of the test pile; Then, inject silicone liquid into the mold. After the silicone solidifies to form a silicone model with a certain strength, pour the rock stratum inclination model to form an inclined rock stratum plate with specific cavities; Repeat the above steps according to the design requirements to finally complete the rock stratum structure required for the pile foundation passing through the karst cave type.

[0009] Preferably, the rock stratum inclination model is made by designing a rock stratum with a specific angle and using the method of single - layer formwork pouring. With the help of a specific foam model, through the pouring process, two types of rock stratum inclination models, namely a right - angled triangular prism and a quadrangular prism with a right - angled trapezoid cross - section, can be shaped to simulate the rock stratum structures with different inclination degrees and shapes in actual engineering. Before use, the foam model is wrapped with a protective film and glued to the two - side wooden boards inside the rock stratum model box, and the prepared silicone model is placed in the predetermined area in the middle of the wooden boards and glued firmly to ensure the stability and integrity of the model during the pouring process, so as to accurately form the rock stratum structure with the required angle and provide a reliable geological simulation environment for the subsequent test.

[0010] Preferably, the rock stratum inclination model is a right - angled triangular prism and a quadrangular prism with a right - angled trapezoid cross - section, and the rock stratum inclination depends on the cross - section angle of the prism body (0° - 60°). According to the finally designed rock stratum division, the right - angled triangular prism is suitable for pouring longer rock strata, and the quadrangular prism with a right - angled trapezoid cross - section is suitable for pouring shorter rock strata. The rock stratum length refers to the cross - section length of the rock stratum.

[0011] Preferably, the foam model and the silicone model have high strength and light - weight characteristics, which can ensure that when the subsequent combined single - layer formwork pouring forms the rock stratum inclination model, its geometric shape is stable, thus ensuring that there is no deviation when the final test pile is embedded.

[0012] Preferably, the described test pile passing through the karst cave is installed synchronously when splicing the inclined rock stratum. The original cement slurry is used in the splicing process, and anti - leakage glue is applied at the contact between the rock stratum and the karst cave to prevent slurry leakage during the secondary pouring of the remaining space, ensuring the close combination and good force transfer between the test pile, the rock stratum, and the karst cave.

[0013] Preferably, four rectangular grooves are provided around the test pile at four different orientations for installing fiber optic strain sensors, and the wires are led out along the grooves on the pile side to the pile end. After installation, the pile grooves are filled and sealed with AB glue. After the AB glue solidifies, the raised parts are polished with a file to ensure the integrity of the pile body.

[0014] Preferably, the detection system consists of fiber optic strain sensors and earth pressure cells. In the test pile preparation process, four grooves are reserved in advance for installing fiber optic strain sensors, and when preparing the inclined rock stratum, the earth pressure cells are placed in the reserved positions and then concrete is poured.

[0015] The beneficial effects of the present invention compared with the existing indoor model test rock stratum pouring method:

[0016] (1) The present invention is a method for vertical bearing test of a bored pile passing through a karst cave in an inclined layered rock stratum, which includes a box body, a rock stratum dip angle model, karst cave preparation, a detection system and a test pile passing through the karst cave. Different from the traditional indoor model test that can only pour horizontal-occurrence rock strata, the present invention can not only fabricate complex inclined rock strata, but also prepare bored piles passing through karst caves, providing an effective means for in-depth study of the bearing deformation characteristics and mechanisms of bored piles passing through karst caves in inclined layered rock strata.

[0017] (2) When making karst caves by the traditional method, the forming process is complex and the accuracy is low, and it is difficult to ensure that the shape and position of the karst cave meet the test requirements. The present invention uses 3D printing technology to prefabricate a karst cave - test pile mold, and by injecting silicone liquid and pouring the rock stratum after solidification, it can accurately form an inclined rock stratum plate with specific cavities, and the combination of the karst cave and the rock stratum is tight, ensuring the stability and integrity of the karst cave during the test, and improving the accuracy and reliability of the test.

[0018] (3) The present invention adopts a block pouring process to immediately place the rock stratum dip angle model into the test frame after completion, reducing the waiting time caused by mold curing. At the same time, the single-layer formwork pouring technology can speed up the production speed while ensuring the integrity of the model (up to 5 - 10 rock stratum plates can be produced in each batch), significantly improving the output efficiency of the indoor test effect and providing more powerful technical support to meet the high-intensity test requirements. Description of the Drawings

[0019] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the specific embodiments of the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0020] Figure 1 is a sectional view of a bored pile model passing through a karst cave in an inclined layered rock stratum provided by the present invention;

[0021] Figure 2It is the sectional view of the inclined rock stratum model box with different cross-section lengths provided by the present invention;

[0022] Figure 3 It is the three-dimensional effect drawing of the 3D printed karst cave - test pile mold provided by the present invention;

[0023] Figure 4 It is the three-dimensional exploded view of the 3D printed karst cave - test pile mold provided by the present invention;

[0024] Figure 5 It is the front view of the combined form of the silicone rubber model provided by the present invention;

[0025] Figure 6 It is the front view of the test pile and the earth pressure cell provided by the present invention.

[0026] In the figure: 1. Test pile; 2. Test model box body; 3. Rock stratum (301 - 314 are the rock stratum serial numbers); 4. Karst cave; 5. Optical fiber sensor; 6. Earth pressure cell; 7. Silicone rubber model (701 - 710 are the silicone rubber serial numbers); 8. Rock stratum dip angle model box; 9. Foam model; 10. 3D printed karst cave - test pile mold. Specific embodiments

[0027] The present invention will be further described in detail below in conjunction with the specific embodiments and with reference to the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention and its applications.

[0028] This embodiment discloses a vertical bearing test method for a foundation pile passing through a karst cave in an inclined layered rock stratum.

[0029] Specific manufacturing method:

[0030] S1: Design the size and select the material of the box body 2 according to the test requirements to ensure that it can accommodate the assembled inclined rock stratum model and related test components, and has sufficient strength and stability. A wooden box body 2 is used, and its internal structure is convenient for the assembly of the inclined rock stratum. Its edges and connection parts are treated with rivets and waterproof adhesives to ensure that it will not deform or be damaged during the rock stratum pouring and testing process.

[0031] S2: First, use 3D printing technology to manufacture the karst cave - test pile mold 10, and customize and cut it to ensure that it can be matched with the rock stratum dip angle model 3 for pouring, and the inner diameter of the mold is slightly larger than the outer diameter of the test pile. Then, pour silicone rubber liquid into the mold 10. After the silicone rubber solidifies to form a silicone rubber model 7 with a certain strength, pour the rock stratum dip angle model to form an inclined rock stratum plate 3 with specific cavities. Repeatedly operate the above steps according to the design requirements to finally complete the rock stratum structure required for the karst cave type pile foundation.

[0032] S3: With the aid of a specific foam model 9, through the pouring process, two types of rock layer dip angle models 3, namely a right triangular prism and a quadrangular prism with a right trapezoidal cross-section, are shaped. Before use, wrap the foam model with a protective film, paste it on both side boards inside the rock layer model box with glue, and place the prepared silicone model 7 in the predetermined area in the middle of the board, and stick it firmly with glue to ensure the stability and integrity of the model during the pouring process. When necessary, a laser locator can be used to calibrate the spatial coordinates of the model to ensure the dip angle deviation.

[0033] S4: For the installation of the test pile 1 passing through the karst cave, install the test pile passing through the karst cave synchronously when splicing the inclined rock layer. The original cement slurry is used during the splicing process, and a rigid clay is thinly coated at the contact between the rock layer and the karst cave to prevent slurry leakage during the secondary pouring of the remaining space, ensuring the close combination and good force transfer between the test pile, the rock layer and the karst cave. Pour a certain thickness for each layer, and cure for the number of days to reach the specified strength after vibration compaction.

[0034] Describe the method for preparing the model in this test, as Figure 1 shown. For the production of the rock layer part of the indoor test model of the foundation pile, the rock layer is made by the method of layered pouring. First, number and mark the dimensions of the rock layer on the drawing, as Figure 2 shown. The pouring rock layer molds are all made of plywood with a waterproof coating. The parts of the foundation pile embedded in the rock layer and the karst cave part need to make integral positioning molds. Mark the auxiliary dotted lines on the mold bottom plate according to the drawing dimensions, and fix the previously prepared silicone model 7 at the bottom of the template. Before use, wrap the foam model 9 with a protective film and paste it on both side boards inside the rock layer model box with glue, as Figure 2 (b) and (c) shown. The rock layer without the karst cave and test pile parts is made into a single-layer pouring mold according to the drawing dimensions, as Figure 2 (c) shown. For the installation of the test pile 1 passing through the karst cave, install the test pile passing through the karst cave synchronously when splicing the inclined rock layer. The original cement slurry is used during the splicing process, and a rigid clay is thinly coated at the contact between the rock layer and the karst cave to prevent slurry leakage during the secondary pouring of the remaining space, ensuring the close combination and good force transfer between the test pile, the rock layer and the karst cave (the mechanical parameters of the contact interface between the rock slabs need to be determined through tests). Pour a certain thickness for each layer, cure for the number of days to reach the specified strength after vibration compaction, and install layer by layer according to the design number until all are completed.

[0035] S5: Installation of the detection system. In the test pile preparation stage, four grooves are reserved in advance for installing the optical fiber strain sensor 5. In this embodiment, the optical fiber strain sensor is installed in four rectangular grooves in different directions of the test pile, and the wire is led out to the pile end along the pile side groove. After the installation is completed, the pile groove is filled and closed with AB glue. After the AB glue solidifies, the raised part is polished with a file to ensure the integrity of the pile body. When preparing the inclined rock layer, the soil pressure box is placed in the reserved position and poured, and the sensor wire is inserted into the stainless steel casing and led out to the data collector.

[0036] Materials and connection methods: It is mainly composed of a wooden box, a rock formation inclination model, a cave-test pile mold, a cave-crossing test pile, and a detection system. Vaseline is applied to the inside of the mold and the surface of the foam model. The wooden box serves as the basic framework of the entire test. Its size and material are designed according to the test requirements and connected by rivets and waterproof adhesives. The rock formation inclination model is made of wooden boards, which are cut and spliced ​​according to the designed rock formation inclination. The wooden boards are glued together, and the prepared silicone model is placed in the predetermined area in the middle of the wooden board and glued with glue. The cave-test pile mold is made of 3D printing technology and matched with the rock formation inclination model to ensure that the shape and position of the cave meet the test requirements. The cave-crossing test pile 1 uses reinforced concrete piles or glass fiber reinforced plastic piles, which are installed simultaneously when splicing the inclined rock formation. The splicing process uses original cement slurry, and waterproof glue is applied at the contact between the rock formation and the cave to prevent leakage and ensure the close connection between the test pile and the rock formation and the cave. After the test pile is pre-buried with the optical fiber sensor, the groove is sealed with AB glue and polished; the soil pressure box is pre-buried at the rock-karst interface, the conductor is led out through a stainless steel casing, and local micro-vibration is used to compact it.

[0037] This specific implementation is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make non-creative modifications to the implementation as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A vertical bearing test method for foundation piles passing through caves in inclined layered rock formations, characterized by: include: Box, rock formation dip model, cave preparation, detection system and test piles through the cave; The box is used to piece together the layers of the inclined rock strata, and finally make a structure similar to a rock foundation; the rock strata inclination model is designed by designing a rock strata with a specific angle and casting it with a single-layer template. The cave preparation cave is 3D printed out of the cave-test pile mold, injected with silicone, and cast into the rock strata; the test piles that cross the cave, after completing the preliminary preparations, are installed simultaneously when splicing the inclined rock strata, and anti-leakage glue is applied at the contact point between the rock strata and the cave, and then the remaining space is cast for the second time; the detection system consists of a fiber optic strain sensor and an earth pressure box. In the test pile preparation stage, four grooves are reserved in advance for installing the fiber optic strain sensor; and when preparing the inclined rock strata, the earth pressure box is placed in the reserved position and then cast.

2. A vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1, characterized in that: The box body is a structure of the inclined rock layer crossing the karst cave pile foundation that is finally made after the inclined rock layer is spliced ​​and the trial piles crossing the karst cave are installed.

3. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1 is characterized by: The rock formation inclination model is molded into two types, namely, a right-angled triangular prism and a quadrangular prism with a right-angled trapezoidal cross section, by means of a specific foam model through a casting process.

4. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1 is characterized by: The foam model is wrapped with a protective film and then glued to the two side wooden boards in the rock formation model box.

5. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1 is characterized by: The cave preparation process is to first make a cave-test pile mold through 3D printing technology, then inject silicone into the mold, and after the silicone is formed, pour the rock layer to finally complete the formation of the cave.

6. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1, characterized in that: The karst cave test pile is formed by prefabricated 3D printing of the karst cave-test pile mold, injecting silicone, and casting the rock layer. The karst cave-test pile mold is custom-cut, and the inner diameter is slightly larger than the outer diameter of the test pile.

7. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1 is characterized by: When pouring the rock layer, the inclination angle of the prepared inclined rock layer is within the range of 0° to 60°.

8. The vertical bearing test method for pile foundations passing through caves in inclined layered rock formations according to claim 1 is characterized by: Four rectangular grooves in different directions are reserved around the test pile for installing the optical fiber strain sensor to lead out its wires.

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