A pile foundation bearing capacity in-situ testing device

Abstract

The utility model discloses a kind of pile foundation bearing capacity in situ testing device, including the main shaft for bearing external force and press into soil layer, the upper installation cylinder being fixedly connected with being penetrated through main shaft and being set as open state at bottom, the side measuring component for measuring pile side resistance being located inside installation cylinder and axially below and sliding along main shaft, the lower installation cylinder being fixedly connected with the bottom of main shaft and being set as open state at bottom being arranged below side measuring component, and the end measuring component for measuring pile end resistance being located inside lower installation cylinder and axially below.The utility model can carry out pile foundation bearing capacity in situ testing, can directly measure the pile side resistance and pile end resistance of each section of pile foundation, and simultaneously measure the displacement corresponding to pile side resistance and pile end resistance, based on pile side resistance and pile end resistance and corresponding displacement, the load displacement curve of each section of pile foundation can be obtained, and pile foundation bearing capacity can be obtained by load transfer method, with high measurement accuracy and reliable measurement result.

Description

Technical Field

[0001] This utility model belongs to the field of bearing capacity testing technology, and in particular relates to an in-situ testing device for pile foundation bearing capacity. Background Technology

[0002] Pile foundations are widely used in high-rise buildings, long-span bridges, and other structures, and their bearing capacity directly determines the safety of the superstructure. To ensure the absolute safety and reliability of pile foundations, bearing capacity testing is necessary. Currently, traditional methods for testing the bearing capacity of pile foundations in civil engineering mainly include the surcharge method, the anchor pile method, and the self-balancing method. These methods directly measure the pile bearing capacity through loading, and cannot directly obtain the end resistance and side resistance of each pile section. When testing the bearing capacity of deep foundations in complex environments such as deep water, steep slopes, and narrow terrain, these traditional testing methods become even more difficult, and the cost of testing ultra-large and ultra-high-tonnage deep foundations is high. Overcoming these technical bottlenecks has become a technical challenge in the industry. Furthermore, in-situ testing is required before designing the bearing capacity of pile foundations. In-situ testing often uses the CPTU method; however, the CPTU method can only roughly estimate the pile bearing capacity and cannot obtain the load-displacement curve of each pile segment, thus making it impossible to accurately calculate the pile bearing capacity in advance. Utility Model Content

[0003] Purpose of the utility model: The purpose of this utility model is to provide an in-situ testing device for pile foundation bearing capacity that can perform in-situ testing and directly obtain the pile end resistance and pile side resistance of the cross section.

[0004] Technical solution: The present invention discloses an in-situ testing device for pile bearing capacity, comprising a main shaft for bearing external forces and pressing into the soil layer, an upper mounting cylinder that passes through the main shaft and is fixedly connected to it with an open bottom, a side measuring component located inside the mounting cylinder and axially downward and sliding along the main shaft for measuring pile side resistance, a lower mounting cylinder located below the side measuring component and fixedly connected to the bottom of the main shaft with an open bottom, and an end measuring component located inside the lower mounting cylinder and axially downward for measuring pile end resistance.

[0005] Furthermore, the side-measuring assembly includes an elastic upper annular rubber sleeve fixedly connected to the bottom of the upper mounting cylinder, an annular bearing plate fixedly connected to the bottom of the upper annular rubber sleeve and passing through the main shaft, a first hydraulic cylinder with its fixed end fixedly connected to the upper mounting cylinder and its free end fixedly connected to the annular bearing plate and used to drive the annular bearing plate to move axially, a first displacement sensor installed in the upper mounting cylinder and used to measure the moving distance of the annular bearing plate, and a friction force measuring element installed at the bottom of the annular bearing plate and in contact with the soil layer.

[0006] Furthermore, the friction force measuring component includes a pressure rod fixedly connected to the bottom of the annular bearing plate, a pressure sensor fixedly connected to the bottom of the pressure rod, a force plate fixedly connected to the pressure sensor, and a friction panel fixedly installed on the outer periphery of the force plate and in contact with the soil layer. A gap is left between the top of the friction panel and the upper annular rubber sleeve, and a space is left between the bottom of the friction panel and the lower mounting cylinder for the friction panel to move downward.

[0007] Furthermore, the friction force measuring device also includes an auxiliary frame that is fixedly connected to the bottom of the annular bearing plate and passes through the main shaft. The auxiliary frame consists of a cylindrical structure with an opening at the bottom and an annular plate disposed on the outer periphery of the bottom of the cylindrical structure. The cylindrical structure is located inside the bearing plate, the annular plate is located below the friction panel, and a gap is left between the bottom of the friction panel and the annular plate.

[0008] Furthermore, the friction force measuring element also includes a lower annular rubber sleeve that is elastically connected to the bottom of the annular plate.

[0009] Furthermore, a linear bearing is fixedly installed on the inner wall of the annular bearing plate to assist its sliding relative to the main shaft.

[0010] Furthermore, the end-measuring assembly includes a second hydraulic cylinder installed inside the lower mounting cylinder, a cone-shaped probe located below the lower mounting cylinder and fixedly connected to the output end of the second hydraulic cylinder, a load sensor installed on the output shaft of the second hydraulic cylinder for measuring resistance, and a second displacement sensor installed inside the lower mounting cylinder for measuring the moving distance of the cone-shaped probe.

[0011] Furthermore, the end-measuring assembly also includes a pore pressure gauge installed on the inner side wall of the bottom end of the lower mounting cylinder for measuring pore pressure. In the initial state, there is a gap between the bottom of the lower mounting cylinder and the cone tip probe.

[0012] Furthermore, it also includes a pressure shaft that is detachably mounted on top of the spindle and used for contact with external drive devices.

[0013] Furthermore, both the main shaft and the pressure shaft have pipeline channels at their centers through which power supply cables and hydraulic pipes pass.

[0014] Beneficial Effects: Compared with existing technologies, this utility model has the following advantages: This utility model can perform in-situ testing of pile foundation bearing capacity, directly measuring the pile side resistance and pile end resistance of each pile segment, and simultaneously measuring the displacement corresponding to the pile side resistance and pile end resistance. Based on the pile side resistance, pile end resistance, and corresponding displacement, the load-displacement curve of each pile segment can be obtained. The pile foundation bearing capacity can be obtained through the load transfer method, with high measurement accuracy and reliable results. This utility model has a compact overall structure and occupies little space, making it suitable for complex environments such as deep water, steep slopes, and narrow terrain. Furthermore, this utility model is easy to operate when testing bearing capacity, effectively reducing testing costs and saving on testing expenses. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0016] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0017] This utility model discloses an in-situ testing device for pile foundation bearing capacity, such as... Figure 1 As shown, the assembly includes a main shaft 1, an upper mounting cylinder 2, a side-measuring component, a lower mounting cylinder 3, an end-measuring component, and a pressure shaft 20. The pressure shaft 20 is detachably mounted on the top of the main shaft 1 and is used to contact an external drive device, causing the pressure shaft 20 to drive the main shaft 1 downwards and press it into the soil layer. Preferably, the top of the main shaft 1 is provided with an external thread, and the bottom of the pressure shaft 20 is provided with a groove that matches the main shaft, and the inner wall of the groove is provided with an internal thread that matches the external thread. The main shaft 1 and the pressure shaft 20 are threadedly connected. The upper mounting cylinder 2 passes through the main shaft 1 and is fixedly connected to it, and the upper mounting cylinder 2 is coaxial with the main shaft 1. The bottom of the upper mounting cylinder 2 is set to an open state. The side-measuring component is located inside the upper mounting cylinder 2 and axially downwards. The side-measuring component can slide along the main shaft 1 and is used to measure the pile side resistance. The lower mounting cylinder 3 is located below the side-measuring component and is fixedly connected to the bottom of the main shaft 1. The lower mounting cylinder 3 is coaxial with the main shaft 1, and the bottom of the lower mounting cylinder 3 is set to an open state. The end-measuring component is located inside and axially below the lower mounting cylinder 3. The end-measuring component is used to measure the pile end resistance.

[0018] like Figure 1As shown, the side-measuring assembly includes an upper annular rubber sleeve 4, an annular pressure plate 5, a first hydraulic cylinder 6, a first displacement sensor 7, a pressure rod 8, a pressure sensor 9, a force plate 10, a friction panel 11, an auxiliary frame 12, a lower annular rubber sleeve 13, and a linear bearing 14. The pressure rod 8, pressure sensor 9, force plate 10, friction panel 11, auxiliary frame 12, lower annular rubber sleeve 13, and linear bearing 14 constitute the friction force measuring component. The upper annular rubber sleeve 4 is fixedly connected to the bottom of the upper mounting cylinder 2 and is made of elastic material. The upper annular rubber sleeve 4 is located on the outer periphery of the main shaft 1. The annular pressure plate 5 is fixedly connected to the bottom of the upper annular rubber sleeve 4, passes through the main shaft 1, and is coaxially arranged with the main shaft 1. The fixed end of the first hydraulic cylinder 6 is fixedly connected to the upper mounting cylinder 2, and the free end is fixedly connected to the annular pressure plate 5. The first hydraulic cylinder 6 is used to drive the annular pressure plate 5 to move axially. The upper annular rubber sleeve 4 is elastic and capable of... The linear bearing 14 is fixedly connected to the inner ring wall of the annular bearing plate 5, and the main shaft 1 is in contact with the inner ring wall of the linear bearing 14. The linear bearing 14 can assist the annular bearing plate 5 to slide along the main shaft 1. The first displacement sensor 7 is installed in the upper mounting cylinder 2 and is used to measure the moving distance of the annular bearing plate 5, that is, to measure the moving distance of the friction force measuring element. The friction force measuring element is installed at the bottom of the annular bearing plate 5, and the outer wall of the friction force measuring element is in contact with the soil layer.

[0019] The pressure rod 8 is fixedly connected to the bottom of the annular bearing plate 5, the pressure sensor 9 is fixedly connected to the bottom of the pressure rod 8, the force plate 10 is fixedly connected to the pressure sensor 9, and the friction panel 11 is fixedly connected to the outer wall of the force plate 10, with the outer side of the friction panel 11 in contact with the soil layer. The auxiliary frame 12 is fixedly connected to the bottom of the annular bearing plate 5 and passes through the main shaft 1. The auxiliary frame 12 is set as a U-shaped annular shape and consists of a cylindrical structure with an opening at the bottom and an annular plate set on the outer periphery of the bottom of the cylindrical structure. The cylindrical structure is located inside the force plate 10, and the annular plate is located below the friction panel 11. The bottom of the lower annular rubber sleeve 13 is fixedly connected to the annular plate, and the bottom of the lower annular rubber sleeve 13 is in contact with the lower mounting cylinder 3. The lower annular rubber sleeve 13 is made of elastic material. The auxiliary frame 12 helps protect the friction panel 11, preventing its bottom from directly contacting the soil. A gap is maintained between the top of the friction panel 11 and the upper annular rubber sleeve 4, and between the bottom of the friction panel 11 and the annular plate. Preferably, the gap is 2-5 mm. These gaps at the top and bottom of the friction panel 11 ensure that it is not subjected to external forces from above or below when moving through the soil; the friction panel 11 is only subjected to external friction, which helps improve the accuracy of the measured pile side resistance. A space is provided between the bottom of the friction panel 11 and the lower mounting cylinder 3 for the friction panel 11 to move downwards, and the lower annular rubber sleeve 13 is located within this space. The elastic design of the upper annular rubber sleeve 4 and the lower annular rubber sleeve 13 provides movement space for the friction panel 11 and prevents soil from entering the upper mounting cylinder 2 and the annular auxiliary frame 12 during measurement. The outer diameters of the pressure shaft 20, upper mounting cylinder 2, upper annular rubber sleeve 4, annular bearing plate 5, friction panel 11, and lower mounting cylinder 3 are equal. Preferably, the material of the friction panel 11 is concrete or steel. In actual application, the material is determined according to the type of pile to be tested. For pipe piles and cast-in-place piles, concrete is used, and for steel pipe piles, steel is used.

[0020] In operation, the first hydraulic cylinder 6 pushes the annular pressure plate 5 downwards. The annular pressure plate 5 moves downwards at a constant speed via the pressure rod 8, pressure sensor 9, force plate 10, and friction panel 11. During this downward movement, the friction panel 11 contacts the soil and generates friction. The load applied downwards by the first hydraulic cylinder 6 is transmitted to the pressure rod 8 via the annular pressure plate 5. The pressure rod 8 then transmits the load to the pressure sensor 9. The pressure sensor 9 measures the load and transmits it to the force plate 10. The force plate 10 then transmits the load to the friction panel 11. Driven by this load, the friction panel 11 moves at a constant speed. Therefore, the load measured by the pressure sensor 9 is equal to the friction force experienced by the friction panel 11. In other words, the pressure sensor 9 is used to measure the friction force experienced by the pressure sensor 9 as it moves through the soil. During the movement of the friction panel 11, the first displacement sensor 7 measures the distance traveled by the friction panel 11. The lateral friction force and load-displacement curves of each soil layer can be obtained from the friction force and displacement of the friction panel 11.

[0021] like Figure 1 As shown, the end-measuring assembly includes a second hydraulic cylinder 15, a cone-shaped probe 16, a load sensor 17, a second displacement sensor 18, and a pore pressure gauge 19. The second hydraulic cylinder 15 is installed inside the lower mounting cylinder 3; the cone-shaped probe 16 is located below the lower mounting cylinder 3, and the output end of the second hydraulic cylinder 15 is fixedly connected to the cone-shaped probe 16; the load sensor 17 is installed on the output shaft of the second hydraulic cylinder 15, and the load sensor 17 is fixedly connected to the output end of this output shaft. Another output shaft is fixedly connected between the other end of the load sensor 17 and the cone-shaped probe 16. The load sensor 17 is used to measure the resistance when the cone-shaped probe 16 moves downwards and inserts into the soil layer; the pore pressure gauge 19 is installed on the inner wall of the bottom end of the lower mounting cylinder 3, and the pore pressure gauge 19 is used to measure the pore pressure. The pore pressure is used in the subsequent load transfer method. When actually using the load transfer method for calculation, the end resistance involved in the calculation needs to be reduced by the excess pore pressure. The load transfer method is an existing mature calculation method and will not be elaborated further here. In the initial state, there is a gap between the bottom of the lower installation cylinder 3 and the cone tip probe 16. Preferably, the gap is 2-5mm. This gap is set to facilitate the measurement of the pore pressure when the lower installation cylinder 3 is located in the current soil layer by the pore pressure gauge 9. On the other hand, it ensures that the cone tip probe 16 is not affected by external forces above when it moves in the soil layer. The cone tip probe 16 is only subject to the resistance of the soil layer, which helps to improve the accuracy of the measured pile end resistance.

[0022] In use, the second hydraulic cylinder 15 drives the cone tip probe 16 to move downwards. The load sensor 17 measures the resistance encountered by the cone tip probe 16 when it moves downwards, which is the load on the cone tip probe 16. The second displacement sensor 18 measures the displacement of the cone tip probe 16 as it moves downwards. The end resistance and load-displacement curves of each soil layer can be obtained by measuring the load and displacement of the cone tip probe 16.

[0023] Both the main shaft 1 and the pressure shaft 20 have a pipeline channel 21 through which the power supply cable passes, which facilitates the connection of the first hydraulic cylinder 6, the first displacement sensor 7, the pressure sensor 9, the second hydraulic cylinder 15, the load sensor 17, the second displacement sensor 18 and the orifice pressure gauge 19 to external cables, transmission cables, hydraulic pipes, etc.

[0024] Before measurement, the entire assembly is pressed into the set depth h1 using pressure shaft 20. Then, the first hydraulic cylinder 6 is adjusted to drive the friction panel 11 downward, and the second hydraulic cylinder 15 is adjusted to drive the cone tip probe 16 downward. The side friction force and end resistance of soil layer h1 are measured. After measurement, the first hydraulic cylinder 6 and the second hydraulic cylinder 15 are reset. Pressure is applied to pressure shaft 20 again to press the entire assembly into the set depth h2. The above steps are repeated to adjust the first hydraulic cylinder 6 and the second hydraulic cylinder 15, and the side friction force and end resistance of soil layer h2 are measured. The above steps are repeated until the design depth hn is reached. The side friction force and end resistance of each soil layer are measured according to requirements. The side friction force and end resistance of different soil layers are processed using the pile foundation load transfer method to generate the pile top load-displacement curve. The bearing capacity of the pile foundation is obtained through the pile top load-displacement curve.

[0025] Traditional in-situ pile foundation bearing capacity testing devices require not only strong vertical and horizontal reactions during measurement, but also reinforcement bars within the pile body to indirectly calculate side and end resistance. Compared to traditional testing methods, this invention solves the problem that traditional in-situ testing cannot obtain load-displacement curves for each pile segment. Furthermore, this invention overcomes the challenge of CPT in-situ testing failing to obtain load-displacement curves for each pile segment's side and end.

Claims

1. An in-situ testing device for pile foundation bearing capacity, characterized in that: It includes a main shaft (1) for bearing external forces and pressing into the soil layer, an upper mounting cylinder (2) that passes through the main shaft (1) and is fixedly connected to it with its bottom open, a side measuring component located inside the mounting cylinder and axially downward and sliding along the main shaft (1) for measuring pile side resistance, a lower mounting cylinder (3) located below the side measuring component and fixedly connected to the bottom of the main shaft (1) with its bottom open, and an end measuring component located inside the lower mounting cylinder (3) and axially downward for measuring pile end resistance.

2. The in-situ pile foundation bearing capacity testing device according to claim 1, characterized in that: The side-measuring assembly includes an elastic upper annular rubber sleeve (4) fixedly connected to the bottom of the upper mounting cylinder (2), an annular bearing plate (5) fixedly connected to the bottom of the upper annular rubber sleeve (4) and passing through the main shaft (1), a first hydraulic cylinder (6) with its fixed end fixedly connected to the upper mounting cylinder (2) and its free end fixedly connected to the annular bearing plate (5) and used to drive the annular bearing plate (5) to move axially, a first displacement sensor (7) installed in the upper mounting cylinder (2) and used to measure the moving distance of the annular bearing plate (5), and a friction force measuring element installed at the bottom of the annular bearing plate (5) and in contact with the soil layer.

3. The in-situ pile foundation bearing capacity testing device according to claim 2, characterized in that: The friction force measuring device includes a pressure rod (8) fixedly connected to the bottom of the annular bearing plate (5), a pressure sensor (9) fixedly connected to the bottom of the pressure rod (8), a force plate (10) fixedly connected to the pressure sensor (9), and a friction panel (11) fixedly installed on the outer periphery of the force plate (10) and in contact with the soil layer. A gap is left between the top of the friction panel (11) and the upper annular rubber sleeve (4), and a space is left between the bottom of the friction panel (11) and the lower mounting cylinder (3) for the friction panel (11) to move downward.

4. The in-situ pile foundation bearing capacity testing device according to claim 3, characterized in that: The friction force measuring device also includes an auxiliary frame (12) that is fixedly connected to the bottom of the annular bearing plate (5) and passes through the main shaft (1). The auxiliary frame (12) consists of a cylindrical structure with an opening at the bottom and an annular plate arranged on the outer periphery of the bottom of the cylindrical structure. The cylindrical structure is located inside the force plate (10), and the annular plate is located below the friction panel (11). A gap is left between the bottom of the friction panel (11) and the annular plate.

5. The in-situ pile foundation bearing capacity testing device according to claim 4, characterized in that: The friction force measuring element also includes a lower annular rubber sleeve (13) that is connected to the bottom of the annular plate and has elasticity.

6. The in-situ pile foundation bearing capacity testing device according to claim 2, characterized in that: A linear bearing (14) is fixedly installed on the inner ring wall of the annular bearing plate (5) to assist its sliding relative to the main shaft (1).

7. The in-situ pile foundation bearing capacity testing device according to claim 1, characterized in that: The end-measuring assembly includes a second hydraulic cylinder (15) installed inside the lower mounting cylinder (3), a cone tip probe (16) located below the lower mounting cylinder (3) and fixedly connected to the output end of the second hydraulic cylinder (15), a load sensor (17) installed on the output shaft of the second hydraulic cylinder (15) for measuring resistance, and a second displacement sensor (18) installed inside the lower mounting cylinder (3) for measuring the moving distance of the cone tip probe (16).

8. The in-situ pile foundation bearing capacity testing device according to claim 7, characterized in that: The end-measuring assembly also includes a pore pressure gauge (19) installed on the inner side wall of the bottom end of the lower mounting cylinder (3) for measuring pore pressure. In the initial state, there is a gap between the bottom of the lower mounting cylinder (3) and the cone tip probe (16).

9. The in-situ pile foundation bearing capacity testing device according to claim 1, characterized in that: It also includes a pressure shaft (20) that is detachably mounted on top of the spindle (1) and used to contact an external drive device.

10. The in-situ pile foundation bearing capacity testing device according to claim 9, characterized in that: Both the main shaft (1) and the pressure shaft (20) have pipeline channels (21) through which power supply cables and hydraulic pipes pass.

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