A load box for pile foundation bearing capacity testing and testing method thereof

Abstract

The present invention relates to a load box for testing pile foundation bearing capacity and a testing method thereof. Several pile-side load boxes are fixed from top to bottom on the outer circumference of a steel cage. The pile-side load boxes, located on the same plane, are symmetrically arranged relative to the steel cage. The pile-side load boxes include an upper box body, a middle box body, a lower box body, and a pressure plate. A pile-end load box is fixed to the bottom end of the steel cage. The pile-end load box includes a spring, a pile-end jack, a pile-end pressure plate, a displacement sensor, and a pressure sensor. The present invention can directly measure pile-side friction and pile-end resistance, significantly reducing testing costs.

Description

Technical Field

[0001] The invention relates to a load box for pile foundation bearing capacity testing and a testing method thereof, and belongs to the field of civil engineering pile foundation bearing capacity testing. Background Art

[0002] Pile foundations are widely used in high-rise buildings, long-span bridges and other buildings and structures, and their bearing capacity directly determines the safety of the superstructure. To ensure the absolute safety and reliability of pile foundations, pile foundation bearing capacity testing is required. Currently, the main methods for testing the bearing capacity of traditional pile foundations include the pile loading method, the anchor pile method, and the self-balancing method. These methods all directly measure the bearing capacity of the pile foundation through loading and cannot directly obtain the pile end side resistance of each cross-section. Traditional testing methods are more difficult for deep foundation bearing capacity testing in complex environments such as deep water, steep slopes, and narrow land. In addition, the cost of testing the bearing capacity of deep foundations with ultra-large sizes and ultra-high tonnage is high.

[0003] How to break through the above technical bottlenecks has become a technical problem in the industry. Summary of the Invention

[0004] The present invention provides a load box for pile foundation bearing capacity testing and a testing method thereof, which can directly measure pile side friction and pile end resistance, greatly saving testing costs.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A load box for testing the bearing capacity of pile foundations, comprising a steel cage, a plurality of pile-side load boxes fixed on the outer circumference of the steel cage from the top to the bottom, wherein the pile-side load boxes located in the same plane are symmetrically arranged relative to the steel cage; and a pile-end load box fixed at the bottom end of the steel cage;

[0007] The inner cavity of the pile side load box is divided into three parts from top to bottom, namely the upper box body, the middle box body and the lower box body, and the upper box body, the middle box body and the lower box body are separable from each other; a pressure plate is installed on the side wall of the pile side load box connected to the steel cage, and a gap is formed between the middle box body and the pressure plate;

[0008] An upper jack is buried in the upper box, and a middle jack is buried in the middle box. When the steel cage that fixes the pile side load box is placed in the pile hole and concrete is poured into the pile hole, the middle jack generates a jacking force to separate the middle box from the upper box. The jacking force of the upper jack is equal to the friction between the middle box and the concrete, which is the side friction force of the pile foundation.

[0009] A pile end jack is buried in the inner cavity of the pile end load box, and a pile end pressure plate is covered on the bottom of the pile end load box. The push rod of the pile end jack is connected to the pile end pressure plate. When pouring concrete into the pile hole, the pushing force of the pile end jack is the pile end resistance.

[0010] As a further preferred embodiment of the present invention, in the upper section box, an upper jack is buried in the center of the upper section box, a push rod of the upper jack is connected to the top of the middle section box, and a pressure sensor is arranged at the connection between the push rod of the upper jack and the middle section box;

[0011] Install a displacement sensor on the side wall of the upper jack;

[0012] One end of the upper jack is a push rod, and the other end is provided with a reinforced base, which is reinforced with steel bars;

[0013] As a further preferred embodiment of the present invention, in the cavity of the upper box, transverse jacks are respectively installed on both sides of the upper jack, with their push rods facing the pressure plate;

[0014] The upper box is connected to the steel cage by fixing bolts;

[0015] As a further preferred embodiment of the present invention, in the middle section box, a central jack is buried in the center of the middle section box, a push rod of the central jack is connected to the top of the lower section box, and a pressure sensor is arranged at the connection between the push rod of the central jack and the lower section box;

[0016] Install a displacement sensor on the side wall of the center jack;

[0017] One end of the center jack is a push rod, and the other end is provided with a reinforced base, which is reinforced with steel bars;

[0018] As a further preferred embodiment of the present invention, there is a side wall with a gap between the middle box body and the pressure plate, and pulley grooves are respectively opened on the pressure plates on both sides of the central jack on this side wall, and a plurality of pulleys are arranged in the pulley grooves, and also include a plurality of pulley rollers, and the end of each pulley roller is connected to the pressure plate, and the pulley is sleeved on the pulley roller;

[0019] The gap between the middle box and the pressure plate provides space for the pulley to move;

[0020] As a further preferred embodiment of the present invention, a panel is provided on the top opening adjacent to the lower box and the middle box, and a plurality of partitions are arranged in the inner cavity of the lower box below the panel. There are gaps between the top panel and the partitions, and between adjacent partitions, and the gaps are filled with high-compression sponge.

[0021] As a further preferred embodiment of the present invention, a transverse jack is installed in the cavity of the lower box body, the transverse jack located in the lower box body matches the transverse jack located in the upper box body, and the push rod of the transverse jack faces the pressure plate;

[0022] The lower box is connected to the steel cage by fixing bolts;

[0023] As a further preferred embodiment of the present invention,

[0024] The pile end load box is fixed to the bottom end of the steel cage by a spring;

[0025] In the pile end load box, the pile end jack is buried in the center of the pile end load box, the push rod of the pile end jack is connected to the pile end pressure plate, and a load sensor is arranged at the connection between the push rod of the pile end jack and the pile end pressure plate;

[0026] Install a displacement sensor on the side wall of the pile end jack;

[0027] One end of the pile end jack is a push rod, and the other end is provided with a reinforcement base, which is reinforced with steel bars;

[0028] The test method based on the load box for pile foundation bearing capacity testing specifically includes the following steps:

[0029] Step S1: Determine the size of the pile side load box and the pile end load box according to the size of the steel cage and the pile hole;

[0030] Step S2: Determine the spacing and placement positions of the pile side load boxes on the reinforcement cage according to the soil layer where the pile hole is located. When placing the pile side load boxes, the pile side load boxes on the same horizontal line are symmetrically arranged.

[0031] Step S3: Fix the pile side load box to the steel cage with fixing bolts, and fix the pile end load box to the bottom end of the steel cage with springs to form a pile skeleton;

[0032] Step S4: placing the steel cage into the pile hole, and the pile side load box contacts the inner wall of the pile hole through the transverse jack;

[0033] Step S5: pouring concrete into the pile skeleton. When the concrete strength in the pile reaches 80% of the design strength, the middle jack is started to push toward the bottom of the pile hole, squeezing the high-compression sponge in the lower box to form a cavity in the lower box. The upper jack is then started to push the middle box into the cavity formed by the lower box, and finally the pile end jack is pushed.

[0034] Step S6: loading the pile side load box and the pile end load box in stages until the load reaches the loading limit of the pile side load box or the pile end load box, and then terminating the loading;

[0035] Step S7: After the graded loading is completed, the load-displacement relationship of the pile foundation is obtained by using the load transfer method according to the obtained load-displacement curve of the pile hole soil layer, and then the ultimate bearing capacity of the pile foundation is obtained;

[0036] As a further preferred embodiment of the present invention, step S6 is the same as the steps of performing graded loading on the pile side load box and the pile end load box, specifically:

[0037] Step S61: setting each level of load to 1 / 10 of the maximum load value, and setting the first level load to 2 times the graded load;

[0038] Step S62: When each level of load is applied to the pile side load box or the pile end load box, the displacement is measured by the displacement sensor at 5 minutes, 15 minutes, 30 minutes, 45 minutes and 60 minutes. After 60 minutes, the displacement is measured every 30 minutes.

[0039] Step S63: Determine whether the displacement change rate reaches the set standard. If so, apply the next level of load to the pile side load box or the pile end load box. If not, continue with the same level of load.

[0040] The specific setting standard is that starting from the 30th minute after the load is applied, the displacement readings of the displacement sensor every 30 minutes are selected for calculation three times within 1.5 hours, and the displacement increment within each hour is less than or equal to 0.1mm, and the displacement increment is less than or equal to 0.1mm for two consecutive times;

[0041] Step S64: Based on step S63, a graded load is applied to the pile side load box or the pile end load box. When the displacement increment of the upper box or the lower box of the pile side load box is greater than twice the displacement increment under the previous level of load, the load reaches the loading limit of the pile side load box and the loading is terminated.

[0042] Through the above technical solution, compared with the existing technology, the present invention has the following beneficial effects:

[0043] 1. The load box for pile foundation bearing capacity testing provided by the present invention is based on the fact that pile foundation bearing capacity is composed of pile side friction and pile end resistance. Therefore, as long as the pile-soil friction and pile end resistance of each soil layer are measured, the pile foundation bearing capacity can be obtained through the load transfer method;

[0044] 2. The testing method of the load box for pile foundation bearing capacity testing provided by the present invention can directly measure the pile side friction and pile end resistance, which solves the difficulties of traditional testing methods for deep foundation bearing capacity in complex environments such as deep water, steep slopes, and narrow land, and greatly reduces the cost of testing the bearing capacity of oversized and over-tonnage deep foundations. At the same time, the pile side load box and pile end jack used are small in size, which greatly saves testing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described below with reference to the accompanying drawings and examples.

[0046] Figure 1 This is a schematic diagram of the pile side load box structure in a preferred embodiment provided by the present invention;

[0047] Figure 2This is a schematic diagram of the pile end load box structure in a preferred embodiment provided by the present invention;

[0048] Figure 3 It is a structural schematic diagram after the pile side load box and the pile end load box provided by the present invention are installed in the pile hole through the steel cage.

[0049] In the figure: 1 is the pile side load box, 2 is the pressure plate, 3 is the upper box body, 4 is the middle box body, 5 is the lower box body, 6 is the reinforcement base, 7-1 is the upper jack, 7-2 is the middle jack, 7-3 is the pile end jack, 9 is the transverse jack, 10 is the fixing bolt, 11 is the pulley groove, 12 is the pulley, 13-1 is the panel, 13-2 is the partition, 13-3 is the high compression sponge, 14 is the load sensor, 15 is the displacement sensor, 16 is the pile end load box, 17 is the pile end pressure plate, 18 is the spring, 19 is the steel cage, 20 is the pipe, and 21 is the inner wall of the pile hole. Implementation Method

[0050] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side", "right side", "upper", "lower", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are intended only to facilitate the description of the present invention and simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second", etc. do not indicate the importance of the components and therefore should not be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrative purposes only and do not limit the scope of protection of the present invention.

[0051] As explained in the background technology, traditional methods for testing pile foundation bearing capacity all require loading to obtain the pile foundation bearing capacity, which can easily cause pile foundation damage when applying the load. However, relevant tests have found that the pile foundation bearing capacity is actually composed of pile side friction and pile end resistance. Therefore, as long as the pile-soil friction and pile end resistance of each layer of soil are measured, the pile foundation bearing capacity can be obtained through the load transfer method.

[0052] This application provides a load box for pile foundation bearing capacity testing. Figure 3 As shown, a plurality of pile side load boxes 1 are fixed on the outer circumference of the steel cage 19 from the top to the bottom, and the pile side load boxes located in the same plane are symmetrically arranged relative to the steel cage; a pile end load box 16 is fixed at the bottom end of the steel cage; the pile side load box measures the pile side friction force, and the pile end load box measures the pile end resistance, and then the pile foundation bearing capacity can be obtained through the load transfer method.

[0053] Therefore, the pile side load box is an important feature part in the present application. In the preferred embodiment, the inner cavity of the pile side load box is divided into three parts from top to bottom, namely the upper box body 3, the middle box body 4 and the lower box body 5. The upper box body, the middle box body and the lower box body are separable from each other; a pressure plate 2 is installed on the side wall of the pile side load box connected to the steel cage, and there is a gap between the middle box body and the pressure plate.

[0054] As can be seen from the above description, the pile side load box provided in this application is divided into three parts: upper, middle and lower. This is because the friction between the pile hole wall and the soil is measured by moving the middle box. If there is no lower box, then when pouring concrete, the lower box is filled with concrete and the middle box cannot slide. Therefore, the lower box is set. If the middle box is pushed directly through the relevant components in the upper box (the components here are the upper jacks 7-1 mentioned later), the middle box can certainly move downward. However, due to the existence of the lower box, the measured friction also includes the resistance of the lower box, resulting in inaccurate results. Therefore, a component is also set up in the middle box (the component here is the central jack 7-2 mentioned later). First, the central jack in the middle box is pushed to reserve space in the lower box. Then, the upper jack is pushed in the upper box to push the middle box into the reserved space in the lower box to eliminate the resistance at the bottom of the middle box. In this way, the pushing force of the upper jack in the upper box is the friction between the middle box and the soil, so that the side friction of this section of the pile foundation can be obtained.

[0055] The specific structure is as follows Figure 1 As shown, an upper jack is buried in the upper box, and a center jack is buried in the middle box. When the steel cage that fixes the pile side load box is placed in the pile hole and concrete is poured into the pile hole, the center jack generates a jacking force to separate the middle box from the upper box. The jacking force of the upper jack is equal to the friction between the middle box and the concrete, which is the side friction of the pile foundation.

[0056] In the upper box body, the upper jack is buried in the center of the upper box body, the push rod of the upper jack is connected to the top of the middle box body, and a pressure sensor is arranged at the connection between the push rod of the upper jack and the middle box body; a displacement sensor 15 is installed on the side wall of the upper jack; one end of the upper jack is the push rod, and the other end is provided with a reinforcement base 6, which is reinforced with steel bars.

[0057] Within the middle section of the housing, a central jack is embedded in the center of the housing. Its push rod is connected to the top of the lower section, and a pressure sensor is installed at the connection between the push rod and the lower section. A displacement sensor is installed on the side wall of the central jack. The push rod is located at one end of the central jack, and a reinforced base is located at the other end. The reinforced base is reinforced with steel bars. A gap exists between the side walls of the middle section of the housing and the pressure plate. Pulley grooves 11 are provided on the pressure plates on either side of the central jack. Several pulleys 12 are installed in these pulley grooves, along with several pulley rollers. Each pulley roller has its end connected to the pressure plate, and the pulley is sleeved on the pulley roller. The gap between the middle section of the housing and the pressure plate provides space for the pulleys to move.

[0058] A panel 13-1 is provided on the top opening adjacent to the lower section box and the middle section box, and several partitions 13-2 are arranged in the inner cavity of the lower section box below the panel. There are gaps between the top panel and the partitions, and between adjacent partitions, and the gaps are filled with high-compression sponge 13-3.

[0059] The upper, middle, and lower boxes are connected to the steel cage to form the pile skeleton, which is placed in the pile hole. The pile skeleton also needs to accommodate the spacing between the upper and lower boxes relative to the inner wall 21 of the pile hole. Therefore, transverse jacks 9 are installed on either side of the upper jack within the upper box cavity, with their push rods facing the pressure plate. The upper box is connected to the steel cage via fixing bolts 10. Transverse jacks are installed within the lower box cavity, with the positions of the transverse jacks in the lower box matching those in the upper box, and their push rods facing the pressure plate. The lower box is connected to the steel cage via fixing bolts.

[0060] Next, the structure of the pile end load box is described. Figure 2 As shown, the pile end load box is fixed to the bottom of the steel cage via a spring 18. A pile end jack 7-3 is embedded in the center of the pile end load box. The pile end jack's push rod is connected to the pile end pressure plate 17. A load sensor 14 is installed at the connection between the push rod and the pile end pressure plate. Displacement sensors are installed on the side walls of the pile end jack. The pile end jack has a push rod at one end and a reinforced base at the other end, reinforced with steel bars. The pile end jack is embedded in the pile end load box, and the bottom of the pile end load box is covered with a pile end pressure plate. The push rod of the pile end jack is connected to the pile end pressure plate. When pouring concrete into the pile hole, the jack's push force acts as the pile end resistance.

[0061] The description of the load box structure provided in this application involves an upper jack, a middle jack and a pile end jack, and is also matched with a pressure sensor, a displacement sensor and a load sensor. The implementation of these components requires power application, which inevitably involves the connection of each component with a power source. Therefore, a pipe 20 is installed along the central axis of the steel cage and fits against the wall of the steel cage. The wires used to connect the components are sequentially passed through the pipe and extended out of the steel cage to avoid damage to the wires and affect the load test.

[0062] Finally, this application also provides a testing method for a load box for pile foundation bearing capacity testing, which specifically includes the following steps:

[0063] Step S1: Determine the size of the pile side load box and the pile end load box according to the size of the steel cage and the pile hole;

[0064] Step S2: Determine the spacing and placement positions of the pile side load boxes on the reinforcement cage according to the soil layer where the pile hole is located. When placing the pile side load boxes, the pile side load boxes on the same horizontal line are symmetrically arranged.

[0065] Step S3: Fix the pile side load box to the steel cage with fixing bolts, and fix the pile end load box to the bottom end of the steel cage with springs to form a pile skeleton;

[0066] Step S4: placing the steel cage into the pile hole, and the pile side load box contacts the inner wall of the pile hole through the transverse jack;

[0067] Step S5: pouring concrete into the pile skeleton. When the concrete strength in the pile reaches 80% of the design strength, the middle jack is started to push toward the bottom of the pile hole, squeezing the high-compression sponge in the lower box to form a cavity in the lower box. The upper jack is then started to push the middle box into the cavity formed by the lower box, and finally the pile end jack is pushed.

[0068] Step S6: loading the pile side load box and the pile end load box in stages until the load reaches the loading limit of the pile side load box or the pile end load box, and then terminating the loading;

[0069] Step S7: After the graded loading is completed, the load-displacement relationship of the pile foundation is obtained by using the load transfer method according to the obtained load-displacement curve of the pile hole soil layer, and then the ultimate bearing capacity of the pile foundation is obtained.

[0070] Step S6 is the same as the steps for performing graded loading on the pile side load box and the pile end load box, specifically:

[0071] Step S61: Use equal loading in each level, set the load of each level to 1 / 10 of the maximum load value, and set the first level load to 2 times the graded load; at the same time, during loading and unloading, the load should be transferred evenly, continuously, and without impact, and the variation of each level load during the maintenance process should not exceed ±10% of the graded load;

[0072] Step S62: When each level of load is applied to the pile side load box or the pile end load box, the displacement is measured by the displacement sensor at 5 minutes, 15 minutes, 30 minutes, 45 minutes and 60 minutes. After 60 minutes, the displacement is measured every 30 minutes.

[0073] Step S63: Determine whether the displacement change rate reaches the set standard. If so, apply the next level of load to the pile side load box or the pile end load box. If not, continue with the same level of load.

[0074] The specific setting standard is that starting from the 30th minute after the load is applied, the displacement readings of the displacement sensor every 30 minutes are selected for calculation three times within 1.5 hours, and the displacement increment within each hour is less than or equal to 0.1mm, and the displacement increment is less than or equal to 0.1mm for two consecutive times;

[0075] Step S64: Based on step S63, a graded load is applied to the pile-side load box or the pile-end load box. When the displacement increment of the upper or lower section of the pile-side load box exceeds twice the displacement increment under the previous level of load, the load reaches the pile-side load box loading limit, and loading is terminated. Generally, according to standards, when the displacement increment of the upper or lower section of the pile-side load box exceeds five times the displacement increment under the previous level of load, the total displacement exceeds 40 mm.

[0076] In summary, deep foundations are widely used in high-rise buildings, long-span bridges and other buildings (structures), and their bearing capacity directly determines the safety of the superstructure. The load box and test method for pile foundation bearing capacity testing provided in this application can not only directly measure the pile side friction and pile end resistance, but also the pile side load box and pile end load box are small in size, which greatly saves testing costs. It solves the difficulties of traditional deep foundation bearing capacity testing methods in complex environments such as deep water, steep slopes, and narrow land, and greatly reduces the cost of testing the bearing capacity of oversized and over-tonnage deep foundations.

[0077] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0078] The meaning of "and / or" in this application means that both situations where each exists alone or both exist at the same time are included.

[0079] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0080] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A load box for pile foundation bearing capacity testing, comprising a steel cage (19), characterized in that: A plurality of pile side load boxes (1) are fixed from the top to the bottom on the outer circumference of the steel cage (19), and the pile side load boxes (1) located in the same plane are symmetrically arranged relative to the steel cage (19); a pile end load box (16) is fixed at the bottom end of the steel cage (19); The inner cavity of the pile side load box (1) is divided into three parts from top to bottom, namely an upper box body (3), a middle box body (4) and a lower box body (5), and the upper box body (3), the middle box body (4) and the lower box body (5) are separable from each other; a pressure plate (2) is installed on the side wall of the pile side load box (1) connected to the steel cage (19), and a gap is provided between the middle box body (4) and the pressure plate (2); An upper jack (7-1) is embedded in the upper box (3), and a middle jack (7-2) is embedded in the middle box (4). When the steel cage (19) of the fixed pile side load box (1) is placed in the pile hole and concrete is poured into the pile hole, the middle jack (7-2) generates a top force to separate the middle box (4) from the upper box (3). The top force of the upper jack (7-1) is equal to the friction between the middle box (4) and the concrete, which is the side friction of the pile foundation. A pile end jack (7-3) is buried in the inner cavity of the pile end load box (16), a pile end pressure plate (17) is covered on the bottom of the pile end load box (16), a push rod of the pile end jack (7-3) is connected to the pile end pressure plate (17), and when concrete is poured into the pile hole, the top force of the pile end jack (7-3) is the pile end resistance.

2. The load box for pile foundation bearing capacity testing according to claim 1, characterized in that: In the upper section box (3), the upper jack (7-1) is buried at the center of the upper section box (3), the push rod of the upper jack (7-1) is connected to the top of the middle section box (4), and a pressure sensor is arranged at the connection between the push rod of the upper jack (7-1) and the middle section box (4); A displacement sensor (15) is installed on the side wall of the upper jack (7-1); One end of the upper jack (7-1) is a push rod, and the other end thereof is provided with a reinforcement base (6), which is reinforced with steel bars.

3. The load box for pile foundation bearing capacity testing according to claim 2, characterized in that: In the inner cavity of the upper box (3), transverse jacks (9) are respectively installed on both sides of the upper jack (7-1), with their push rods facing the pressure plate (2); The upper box body (3) is connected to the steel cage (19) via fixing bolts (10).

4. The load box for pile foundation bearing capacity testing according to claim 1, characterized in that: In the middle section box (4), the middle jack (7-2) is buried at the center of the middle section box (4), the push rod of the middle jack (7-2) is connected to the top of the lower section box (5), and a pressure sensor is arranged at the connection between the push rod of the middle jack (7-2) and the lower section box (5); A displacement sensor (15) is installed on the side wall of the center jack (7-2); One end of the central jack (7-2) is a push rod, and the other end thereof is provided with a reinforcement base (6), which is reinforced with steel bars.

5. The load box for pile foundation bearing capacity testing according to claim 4, characterized in that: A side wall with a gap between the middle box body (4) and the pressure plate (2) is provided. Pulley grooves (11) are respectively provided on the pressure plates (2) on both sides of the middle jack (7-2). A plurality of pulleys (12) are arranged in the pulley grooves (11). The pulley rollers also include a plurality of pulley rollers. The end of each pulley roller is connected to the pressure plate (2). The pulley (12) is sleeved on the pulley roller. The gap between the middle box body (4) and the pressure plate (2) provides a movable space for the pulley (12).

6. The load box for pile foundation bearing capacity testing according to claim 1, characterized in that: A panel (13-1) is provided on the top opening adjacent to the lower section box (5) and the middle section box (4); a plurality of partitions (13-2) are arranged below the panel (13-1) in the inner cavity of the lower section box (5); and there are gaps between the top panel (13-1) and the partitions (13-2), as well as between adjacent partitions (13-2), and the gaps are filled with a high-compression sponge (13-3).

7. The load box for pile foundation bearing capacity testing according to claim 6, characterized in that: A transverse jack (9) is installed in the inner cavity of the lower section box (5), the transverse jack (9) located in the lower section box (5) matches the transverse jack (9) located in the upper section box (3), and the push rod of the transverse jack (9) faces the pressure plate (2); The lower box body (5) is connected to the steel cage (19) via fixing bolts (10).

8. The load box for pile foundation bearing capacity testing according to claim 1, characterized in that: The pile end load box (16) is fixed to the bottom end of the steel cage (19) through a spring (18); In the pile end load box (16), the pile end jack (7-3) is buried at the center of the pile end load box (16), the push rod of the pile end jack (7-3) is connected to the pile end pressure plate (17), and a load sensor (14) is arranged at the connection between the push rod of the pile end jack (7-3) and the pile end pressure plate (17); Installing a displacement sensor (15) on the side wall of the pile end jack (7-3); One end of the pile end jack (7-3) is a push rod, and the other end thereof is provided with a reinforcement base (6), which is reinforced with steel bars.

9. The method for testing a load box for pile foundation bearing capacity testing according to any one of claims 1 to 8, characterized in that: The specific steps include: Step S1: Determine the size of the pile side load box (1) and the pile end load box (16) according to the size of the steel cage (19) and the size of the pile hole; Step S2: determining the spacing and placement positions of the pile side load boxes (1) on the steel cage (19) according to the soil layer where the pile hole is located. When placing the pile side load boxes (1) on the same horizontal line, the pile side load boxes (1) are symmetrically arranged. Step S3: fixing the pile side load box (1) to the steel cage (19) through fixing bolts (10), and fixing the pile end load box (16) to the bottom end of the steel cage (19) through springs (18) to form a pile skeleton; Step S4: placing the steel cage (19) into the pile hole, and the pile side load box (1) contacts the inner wall (21) of the pile hole through the transverse jack (9); Step S5: pouring concrete into the pile skeleton, and when the concrete strength in the pile reaches 80% of the design strength, starting the middle jack (7-2), which pushes toward the bottom of the pile hole, squeezing the high-compression sponge (13-3) in the lower box (5), forming a cavity in the lower box (5), continuing to start the upper jack (7-1), pushing the middle box (4), pushing the middle box (4) into the cavity formed by the lower box (5), and finally pushing the pile end jack (7-3); Step S6: loading the pile side load box (1) and the pile end load box (16) in stages until the load reaches the loading limit of the pile side load box (1) or the pile end load box (16), and then terminating the loading; Step S7: After the graded loading is completed, the load-displacement relationship of the pile foundation is obtained by using the load transfer method according to the obtained load-displacement curve of the pile hole soil layer, and then the ultimate bearing capacity of the pile foundation is obtained.

10. The method for testing a load box for pile foundation bearing capacity testing according to claim 9, characterized in that: Step S6 is the same as the steps for performing graded loading on the pile side load box (1) and the pile end load box (16), specifically: Step S61: setting each level of load to 1 / 10 of the maximum load value, and setting the first level load to 2 times the graded load; Step S62: When each level of load is applied to the pile side load box (1) or the pile end load box (16), the displacement is measured by the displacement sensor (15) at 5 minutes, 15 minutes, 30 minutes, 45 minutes and 60 minutes. After 60 minutes, the displacement is measured every 30 minutes. Step S63: Determine whether the displacement change rate reaches the set standard. If it reaches the standard, apply the next level of load to the pile side load box (1) or the pile end load box (16). If it does not reach the set standard, continue to apply the same level of load. The specific setting standard is that starting from the 30th minute after the load is applied, the displacement measured by the displacement sensor (15) every 30 minutes for three times within 1.5 hours is selected for calculation, and the displacement increment within each hour is determined to be less than or equal to 0.1 mm, and the displacement increment is less than or equal to 0.1 mm for two consecutive times; Step S64: Based on step S63, a graded load is applied to the pile side load box (1) or the pile end load box (16). When the displacement increment of the upper box (3) or the lower box (5) of the pile side load box (1) is greater than twice the displacement increment under the previous level of load, the load reaches the loading limit of the pile side load box (1), and the loading is terminated.

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