Static load testing device and method

Abstract

A static load test device and method, including a detection unit for detecting the amount of foundation pit settlement and a force application unit for applying load to the test point, the force application unit is arranged in the foundation pit through a plurality of support rods which provide lateral support for the force application unit, the force application unit includes a top plate and a bottom plate, the edges of the top plate and the bottom plate are connected through a flexible piece to form a material containing bag with a containing cavity, the containing cavity is filled with a liquid-like medium formed by mixing three kinds of steel balls and lubricating oil, the particle size ratio of the steel balls is 1:3:6; a pressure sensor for detecting the load of the test point is arranged at the center position of the bottom plate, a measurement identification point is arranged at the center position of the top plate, the detection unit includes a displacement sensor for detecting the distance between the top plate and the bottom plate and a total station instrument arranged outside the foundation pit and used for detecting the height of the measurement identification point. The present application reduces the volume of the test device, facilitates installation, avoids the problem of local accumulation in the detection device, and makes the static load test result more accurate.

Description

Technical Field

[0001] This invention relates to the field of static load testing technology, specifically to a static load testing apparatus and method. Background Technology

[0002] In civil engineering construction, static load testing is the optimal method for determining the bearing capacity of foundation pits, pile foundations, and composite foundations of large buildings. In existing technologies, static load testing requires placing a bearing plate on the foundation surface, with weight blocks on top and jacks underneath. The jacks apply progressively increasing loads to the test points, and the settlement of the bearing plate under each load is measured. However, this method has the following drawbacks:

[0003] 1. The reaction device for static load tests is either a concrete counterweight or a ground anchor system. When placing the concrete counterweight on the bearing plate, a crane and transport vehicles are required for handling, resulting in high transportation and hoisting costs. Furthermore, narrow streets in some urban areas make it difficult to hoist the counterweight. Ground anchor systems are mostly used when the soil in the foundation pit is relatively good. If the soil is loose, the ground anchor system is unlikely to provide the required reaction force for the test. Installing the reaction device near the test point can easily damage the soil layer, causing the test data to become invalid.

[0004] 2. The load applied to the test point is measured by jacks, and the load is applied to the test point step by step by jacks. The jacks are installed below the support plate. There are safety issues in the installation process, and an additional oil pump is required for testing.

[0005] Therefore, the patented detection device and method for static load testing (patent number: CN201510420546.7) uses water as a counterweight. The loading and unloading process is controlled by the volume of water in the detection device, avoiding the inconvenience and time-consuming loading and unloading of heavy objects in conventional detection methods. Furthermore, during the testing process, load data is not read by lifting jacks; monitoring is performed simultaneously with water injection. However, water, as a force-applying medium, has a low density, requiring a very large volume of water to reach the load at the test point, thus necessitating a large detection device, which is inconvenient to install. If a higher-density solid medium is added to the detection device to load the test point, the poor fluidity of the solid medium will cause localized accumulation, leading to uneven loading of the detection device. Simultaneously, during the test, the flow of localized accumulation due to external factors can affect the load at the test point, thus impacting the accuracy of the test. Summary of the Invention

[0006] To address the problem of localized accumulation caused by the poor fluidity of solid media in existing technologies, this invention provides a static load testing device and method that reduces the size of the testing device, making it easier to install; it also avoids the problem of localized accumulation within the testing device, resulting in more accurate static load test results.

[0007] To achieve the above objectives, the specific solution adopted by the present invention is as follows: a static load testing device, comprising a detection unit for detecting the settlement of a foundation pit and a force application unit for applying load to a test point. The force application unit is installed in the foundation pit by multiple support rods providing lateral support. The force application unit comprises a top plate and a bottom plate, the edges of which are connected by a flexible component to form a sac with a receiving cavity. The sac is filled with a quasi-liquid medium formed by mixing steel balls of three different particle sizes with lubricating oil, the particle size ratio of which is 1:3:6. A pressure sensor for detecting the load at the test point is located at the center of the bottom plate, and a measurement marker is located at the center of the top plate. The detection unit includes a displacement sensor for detecting the distance between the top and bottom plates and a total station located outside the foundation pit for detecting the height of the measurement marker.

[0008] As an optimized solution for the above-mentioned static load testing device: multiple sets of collars corresponding to the support rod and capable of being fitted onto the support rod are provided on the outer side of the flexible component, and each set of collars is coaxially arranged and spaced apart along the height direction of the flexible component.

[0009] As another optimized solution for the above-mentioned static load testing device: a boss is formed at the center of the base plate, the lower surface of the boss is in contact with the test point, and the pressure sensor is set on the lower surface of the boss.

[0010] As another optimized solution for the above-mentioned static load test device: the top plate has an inlet for a liquid-like medium to enter the containment cavity, and the bottom plate has an outlet for a liquid-like medium to flow out of the containment cavity.

[0011] As another optimized solution for the above-mentioned static load testing device, the top plate is provided with multiple vent holes.

[0012] As another optimized solution for the aforementioned static load testing device: the diameters of the steel balls are 10mm, 30mm, and 60mm, and the mass ratio of the three should satisfy: m 60 :m 10 ≥5, m 30 2 = 1-3; and each cubic meter of steel balls is mixed with 1kg-5kg of lubricating oil.

[0013] As another optimized solution for the above-mentioned static load test device: the diameters of the steel balls are 10mm, 30mm and 60mm respectively, the mass ratio of the three is 1:3:5, and each cubic meter of steel ball is mixed with 1kg-5kg of lubricating oil.

[0014] A static load testing method, based on the aforementioned static load testing apparatus, includes the following steps:

[0015] S1, the material bladder is placed in the pit by the support rod, and the center of the bottom plate is placed on the test point. The top plate is in a horizontal state. The initial distance l0 between the top plate and the bottom plate is detected by the displacement sensor, and the initial height h0 of the measurement mark point is detected by the total station.

[0016] S2, Pour a liquid-like medium into the container until the load at the test point reaches the first-level test target value. After the liquid-like medium enters the container, the upper surface is in a horizontal state. The real-time distance l between the top plate and the bottom plate is detected by a displacement sensor. 实 The real-time height h of the marker point was detected and measured using a total station. 实 The settlement amount is obtained based on the initial spacing l0 and the initial height h0;

[0017] S3, repeat S2 above until the test targets for each level are completed, and extract the liquid-like medium from the container.

[0018] As an optimized solution to the above-mentioned static load test method: In S2, the settlement is (h 实 -l 实 )-(h0-l0).

[0019] As an alternative optimization of the above-mentioned static load test method: in step S2, a liquid-like medium is injected into the container at a rate of 10 kPa / min until the load at the test point reaches 90% of the first-level test target value; then, a liquid-like medium is injected into the container at a rate of 1 kPa / min until the load at the test point reaches the first-level test target value.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention provides a static load testing device and method. The container is filled with a liquid-like medium formed by a mixture of steel balls of three different particle sizes and lubricating oil. The particle size ratio of the steel balls is 1:3:6. The steel balls have a high density, so the volume of steel balls required for the same load is small, which facilitates transportation and reduces the volume of the testing device, making the installation of the testing device easier. Furthermore, the smaller-diameter steel balls can be inserted between the larger-diameter steel balls, reducing the porosity of the steel balls and obtaining the maximum mass under the minimum volume condition, further reducing the volume of the testing device. The liquid-like medium has good fluidity, avoiding local accumulation that could lead to uneven forces within the container and improving the accuracy of the test results.

[0022] 2. In this invention, a total station and displacement sensors are used to detect the settlement at the test points, so that the detection of settlement is not affected by the sinking of the foundation pit, thus making the detection of settlement more accurate.

[0023] 3. This invention provides a static load test method in which the speed of the liquid-like medium is different in the early and late stages of the injection, so as to avoid the influence of the force of the liquid-like medium falling in the later stage on the pressure sensor detection, and make the value detected by the pressure sensor more stable. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a schematic diagram of the top plate of the present invention;

[0026] Figure 3 This is a schematic diagram of the exhaust port structure;

[0027] Figure 4 This is a schematic diagram of the installation of each component in this invention;

[0028] Reference numerals: 1. Support rod, 2. Flexible component, 201. Collar, 3. Top plate, 301. Inlet, 302. Exhaust port, 303. Measurement marker, 4. Bottom plate, 401. Outlet, 402. Boss, 5. Displacement sensor, 6. Transmitter, 7. Pressure sensor, 8. Mixer truck, 9. Total station. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of the present invention should be understood as prior art known or should be known by those skilled in the art, such as the connection method between the flexible component 2 and the top plate 3 and the bottom plate 4, the installation method of the displacement sensor 5 and the top plate 3 and the bottom plate 4, the detection method of the displacement sensor 5, and the working process of the total station 9.

[0030] Example 1

[0031] A static load testing device includes a detection unit for detecting the settlement of a foundation pit and a force application unit for applying load to test points. The force application unit is installed in the foundation pit by multiple support rods 1 that provide lateral support. The force application unit includes a top plate 3 and a bottom plate 4. The edges of the top plate 3 and the bottom plate 4 are connected by a flexible member 2 to form a cavitary with a receiving cavity. In this embodiment, both the top plate 3 and the bottom plate 4 are rectangular plate structures and are made of steel plates. The flexible member 2 is a foldable and stretchable polyethylene industrial plastic sheet, meaning that the flexible member 2 can be expanded along its height direction. After expansion, the flexible member 2 is a rectangular cylindrical structure with openings at both ends. The upper end face of the flexible member 2 is fixedly and sealed to the top plate 3, and the lower end face of the flexible member 2 is fixedly and sealed to the bottom plate 4. A cavitary with a receiving cavity is formed between the top plate 3, the bottom plate 4, and the flexible member 2. There are four support rods 1 distributed at the four corners of the top plate 3. In this embodiment, the four corners of the top plate 3 and the bottom plate 4 have through holes corresponding to the support rods 1 and allowing them to pass through. The outer side of the flexible member 2 is provided with multiple sets of collars 201 corresponding to the support rods 1 and able to be fitted onto the support rods 1. Each set of collars 201 is coaxially arranged and spaced apart along the height direction of the flexible member 2. In this embodiment, there are four sets of collars 201 corresponding to the support rods 1. Each set of collars 201 is coaxially arranged with the corresponding through holes of the top plate 3 and the bottom plate 4. When installing the test device, the bottom end of the support rod 1 passes through the through holes of the top plate 3, the collars 201 and the through holes of the bottom plate 4 in sequence and is inserted into the pit. At this time, the center position of the bottom plate 4 is in contact with the test point, and the top plate 3 is in a horizontal state. The support rod 1 only provides lateral support for the bladder. The collars 201 and the top plate 3 can move along the height direction of the support rod 1, that is, the distance between the top plate 3 and the bottom plate 4 is variable.

[0032] The container is filled with a quasi-liquid medium formed by a mixture of steel balls of three different particle sizes and lubricating oil. The load on the test points is applied by the gravity of this quasi-liquid medium. The amount of quasi-liquid medium is controlled to meet different load requirements at the test points. The density of the quasi-liquid medium is greater than that of water; therefore, under the same load, its volume is much smaller than that of water, reducing the size of the test apparatus and facilitating installation. Furthermore, the quasi-liquid medium does not require cranes or transport vehicles for handling, reducing transportation and lifting costs. Simultaneously, the good fluidity of the quasi-liquid medium prevents localized accumulation that could lead to uneven forces within the container, improving the accuracy of the test results. The particle size ratio of the steel balls is 1:3:6, allowing the smaller-diameter steel balls to be inserted between the larger-diameter balls, reducing porosity. The diameters of the steel balls are 10mm, 30mm, and 60mm, and their mass ratio should satisfy: m 60 :m 10 ≥5, m 30 2The mass ratio of the three components is 1:3:5, which achieves the maximum mass under the minimum volume condition, further reducing the volume of the test device and improving the accuracy of the test results. In this embodiment, each cubic meter of steel balls is mixed with 1kg-5kg of lubricating oil. The lubricating oil reduces or even avoids friction between steel balls and wear caused when the steel balls enter the container. At the same time, the lubricating oil improves the fluidity of the steel balls, keeping the upper surface of the liquid-like medium in the container horizontal, avoiding uneven forces in the container, and ensuring the accuracy of the static load test.

[0033] The top plate 3 has an inlet 301 for the liquid-like medium to enter the receiving cavity, and the bottom plate 4 has an outlet 401 for the liquid-like medium to flow out of the receiving cavity. The top plate 3 has multiple vent holes 302. In this embodiment, the diameter of the vent holes 302 is 10-40 cm. When the liquid-like medium is filled into the receiving bladder, the gas inside the bladder is discharged through the vent holes 302. The vent holes 302 have a mesh structure with 1 cm diameter holes.

[0034] A pressure sensor 7 for detecting the load at the test point is disposed at the center of the base plate 4. A boss 402 is formed protruding downward from the center of the base plate 4. The lower surface of the boss 402 contacts the test point, and the pressure sensor 7 is fixed to the lower surface of the boss 402. Figure 2 As shown, a measurement marker 303 is set at the center of the top plate 3, and the measurement marker 303 is circular.

[0035] In existing technologies, sensors for detecting settlement are typically installed below the reaction device. However, this installation presents safety risks. The sensors are mounted on the reference beam of the reaction device, and settlement of the foundation pit can cause the reference beam to sink, reducing the accuracy of settlement measurement. The detection unit includes displacement sensors 5 for detecting the distance between the top plate 3 and the bottom plate 4, and a total station 9 installed outside the foundation pit for detecting the height of the center position of the measurement marker 303. Two displacement sensors 5 are used, one on the top plate 3 and one on the bottom plate 4, and both sensors are located on the same vertical line. Because the flexible component 2 is a telescopic structure, the distance between the top plate 3 and the bottom plate 4 increases with the increase in the amount of liquid-like medium filling. Therefore, to accurately detect settlement, it is necessary to monitor the distance between the top plate 3 and the bottom plate 4 in real time. The initial height of marker point 303 is measured using a total station 9, and the initial distance between the top plate 3 and the bottom plate 4 is measured using a displacement sensor 5. After applying a corresponding load to the test point, the real-time distance between the top plate 3 and the bottom plate 4 is measured using the displacement sensor 5, and the real-time height of marker point 303 is measured using the total station 9. The settlement of the foundation pit is monitored based on the initial height, initial distance, real-time distance, and real-time height. This reduces the need for a reference beam, and since the total station 9 is located outside the foundation pit, the settlement measurement is not affected by the pit's subsidence, thus making the settlement measurement more accurate.

[0036] In this embodiment, a transmitter 6 is provided at the top of one of the support rods 1. The pressure sensor 7 and the displacement sensor 5 are both connected to the transmitter 6. The pressure sensor 7 and the displacement sensor 5 transmit the detected data to the host computer through the transmitter 6. The data monitored by the total station 9 is transmitted to the host computer, thereby monitoring the settlement of the foundation pit.

[0037] Example 2

[0038] A static load testing method, based on the aforementioned static load testing apparatus, includes the following steps:

[0039] S1, the material container is placed in the pit using support rod 1. The top plate 3 is horizontal. The bottom end of support rod 1 passes through the perforations in the top plate 3, the corresponding collar 201, and the bottom plate 4, and is then inserted into the pit. The length of support rod 1 inserted into the pit is 20-50cm. Support rod 1 provides lateral support for the material container, ensuring that the top plate 3 and collar 201 can move along the height direction of support rod 1. The center position of the bottom plate 4 is placed on the test point. In this embodiment, the lower surface of the boss 402 is in contact with the test point. The total station 9 is installed outside the pit. The initial distance l0 between the top plate 3 and the bottom plate 4 is detected by displacement sensor 5, and the initial height h0 of the measurement marker point 303 is detected and measured by the total station 9. The initial distance and initial height are transmitted to the host computer.

[0040] S2. Steel balls with particle sizes of 10mm, 30mm, and 60mm are placed into the mixer truck 8 in a mass ratio of 1:3:5. Simultaneously, 1kg-5kg of lubricating oil is mixed with each cubic meter of steel balls and stirred to obtain a liquid-like medium. The liquid-like medium is poured into the container until the load at the test point reaches the first-level test target value. Specifically, the liquid-like medium is poured into the container at a rate of 10Kpa / min until the load at the test point reaches 90% of the first-level test target value. Then, the liquid-like medium is poured into the container at a rate of 1Kpa / min until the load at the test point reaches the first-level test target value. This avoids the impact of the falling force of the liquid-like medium on the pressure sensor 7, making the value detected by the pressure sensor 7 more stable. After the liquid-like medium enters the container, the upper surface is in a horizontal state. The real-time distance l between the top plate 3 and the bottom plate 4 is detected by the displacement sensor 5. 实 The real-time height h of marker point 303 was measured using a total station 9. 实 The settlement is obtained based on the initial spacing l0 and the initial height h0. Specifically, the settlement is (h0 - h0) / h0. 实 -l 实 )-(h0-l0).

[0041] S3, repeat S2 above until the test of each level of test target value is completed, extract the liquid-like medium in the container, and let the liquid-like medium flow out through the outlet.

[0042] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A static load testing device, comprising a detection unit for detecting the settlement of a foundation pit and a force application unit for applying load to a test point, wherein the force application unit is disposed within the foundation pit by a plurality of support rods (1) providing lateral support thereto, characterized in that: The force application unit includes a top plate (3) and a bottom plate (4). The edges of the top plate (3) and the bottom plate (4) are connected by a flexible member (2) to form a sac with a receiving cavity. The sac is filled with a liquid-like medium formed by a mixture of steel balls of three different particle sizes and lubricating oil. The particle size ratio of the steel balls is 1:3:

6. A pressure sensor (7) for detecting the load at the test point is set at the center of the bottom plate (4). A measurement marker (303) is set at the center of the top plate (3). The detection unit includes a displacement sensor (5) for detecting the distance between the top plate (3) and the bottom plate (4) and a total station (9) set outside the pit for detecting the height of the measurement marker (303). A boss (402) is formed at the center of the bottom plate (4) protruding downwards. The lower surface of the boss (402) is in contact with the test point, and the pressure sensor (7) is set on the boss. The lower surface of the platform (402); the top plate (3) is provided with an inlet (301) for liquid-like media to enter the containment cavity, and the bottom plate (4) is provided with an outlet (401) for liquid-like media to flow out of the containment cavity; the initial height of the measuring marker point (303) is detected by a total station (9), the initial distance between the top plate (3) and the bottom plate (4) is detected by a displacement sensor (5), after applying the corresponding load to the test point, the real-time distance between the top plate (3) and the bottom plate (4) is detected by a displacement sensor (5), and the real-time height of the measuring marker point (303) is detected by a total station (9) in real time. The settlement of the foundation pit is monitored based on the initial height, initial distance, real-time distance and real-time height; the installation of the reference beam is reduced, and the total station (9) is set outside the foundation pit. The detection of settlement is not affected by the sinking of the foundation pit, thus making the detection of settlement more accurate.

2. The static load testing device as described in claim 1, characterized in that: The flexible component (2) is provided with multiple sets of collars (201) that correspond to the support rod (1) and can be sleeved on the support rod (1). Each set of collars (201) is coaxially arranged and distributed at intervals along the height direction of the flexible component (2).

3. The static load testing device as described in claim 1, characterized in that: The top plate (3) is provided with multiple exhaust holes (302).

4. The static load testing device as described in claim 1, characterized in that: The steel balls have diameters of 10mm, 30mm, and 60mm, and their mass ratio should satisfy: m 60 :m 10 ≥5, m 30 2 :(m 10 ×m 60 =1-3; and each cubic meter of steel balls is mixed with 1kg-5kg of lubricating oil.

5. The static load testing device as described in claim 1, characterized in that: The steel balls have diameters of 10mm, 30mm and 60mm, with a mass ratio of 1:3:5, and each cubic meter of steel balls is mixed with 1kg-5kg of lubricating oil.

6. A static load test method, the method being based on a static load test apparatus according to any one of claims 1-5, characterized in that, Includes the following steps: S1, the material bladder is placed in the pit by the support rod (1), and the center of the bottom plate (4) is placed on the test point. The top plate (3) is in a horizontal state. The initial distance l0 between the top plate (3) and the bottom plate (4) is detected by the displacement sensor (5). The initial height h0 of the measurement mark point (303) is detected by the total station (9). S2, Pour a liquid-like medium into the container until the load at the test point reaches the first-level test target value. After the liquid-like medium enters the container, the upper surface is in a horizontal state. The real-time distance l between the top plate and the bottom plate is detected by the displacement sensor (5). 实 The real-time height h of the measurement marker (303) is detected by a total station (9). 实 The settlement amount is obtained based on the initial spacing l0 and the initial height h0; S3, repeat S2 above until the test results of each level of test target value are completed, and extract the liquid-like medium in the container.

7. The static load test method as described in claim 6, characterized in that: In S2, the settlement amount is (h 实 -l 实 )-(h0-l0).

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