Uplift and horizontal load test device and method for inclined anchor short pile foundation

Abstract

The invention relates to the technical field of composite foundation on-site real-model tests, in particular to an inclined anchor short pile foundation uplift and horizontal load test device and method. Comprising a test rack, a short secondary beam, a datum beam component, a perforated box type secondary beam, a first oil jack, an inclined anchor short pile foundation, a second oil jack and a force transmission cylinder. According to the inclined anchor short pile foundation mechanical property testing device, a more reliable and efficient testing means is provided for deep research on the mechanical property of an inclined anchor short pile foundation, and in addition, key parameters such as the foundation size, the inclined anchor inclination angle and the anchoring form are flexibly adjusted; according to the technical scheme, the influence of different factors on the stress deformation characteristic, the bearing capacity distribution condition and the failure mechanism of the inclined anchor short pile foundation in the actual working condition can be systematically analyzed, and a solid scientific basis is provided for design and construction technology optimization of the inclined anchor short pile foundation.

Description

Technical Field

[0001] The invention relates to the technical field of on-site true-type tests of composite foundations, and in particular to a pull-out and horizontal load test device and method for an inclined anchor short pile foundation. Background Art

[0002] With the acceleration of urbanization, influenced by land planning and urban construction layout, the route selection of transmission lines tends to be in mountainous areas. The construction of transmission lines in mountainous areas has become a normal trend in future power transmission and transformation projects. However, composite strata with thin overburden, good bedrock engineering properties but difficult excavation are widely distributed in the mountainous areas of southwest my country, and wind loads have high instability. These factors make the pile tops prone to large uplift forces and horizontal loads, and traditional foundation forms are difficult to meet engineering needs. For this reason, the inclined anchor short pile foundation came into being as a new type of composite foundation. It combines the vertical bearing capacity of the short pile foundation and the pull-out performance of the inclined anchor rod. It has significant advantages such as low construction difficulty, low material consumption, and strong adaptability to complex geological conditions. It provides an efficient, economical and reliable solution for the construction of transmission lines in mountainous areas.

[0003] At present, the research on inclined anchor short pile foundation mainly focuses on theoretical analysis and numerical simulation, and lacks systematic field test research. The node connection of inclined anchor short pile foundation is complex, and its stress characteristics are greatly affected by the size effect and connection structure. It is urgent to carry out field real-type tests under pull-out + horizontal load to study the stress-deformation characteristics, bearing capacity distribution and failure mode of inclined anchor short pile foundation under actual working conditions. However, most of the existing test devices and methods are aimed at composite foundations (anchor cap foundation, pile-anchor foundation, straight anchor short pile foundation, etc.), and can only apply a single vertical load or horizontal load. There is a lack of field real-type test devices and methods for inclined anchor short pile foundations under pull-out + horizontal loads. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for testing the uplift and horizontal load of an inclined anchor short pile foundation, so as to solve the problem of lack of systematic field test means in existing research and fill the current gap in test loading methods and their supporting equipment.

[0005] To achieve the above-mentioned purpose, the present invention provides a pull-out and horizontal load test device for inclined anchor short pile foundation, the pull-out and horizontal load test device for inclined anchor short pile foundation comprises a test frame, a short secondary beam, a reference beam component, a perforated box-type secondary beam, a first hydraulic jack, an inclined anchor short pile foundation, a second hydraulic jack and a force transmission cylinder, the short secondary beam is transversely installed in the middle of the test frame, the first hydraulic jack is arranged above the short secondary beam, the perforated box-type secondary beam is arranged at the output end of the first hydraulic jack, and the inclined anchor short pile foundation is installed around the perforated box-type secondary beam through a plurality of main bars The oblique anchor short pile foundation is located below the short secondary beam. The test frame is also provided with the second hydraulic jack. The output end of the second hydraulic jack is in contact with the end wall of the oblique anchor short pile foundation through the force transmission cylinder. The test frame is also provided with the reference beam component horizontally arranged. The reference beam component is perpendicular to the short secondary beam. The reference beam component is located above the oblique anchor short pile foundation and below the short secondary beam. Horizontal measuring plates are arranged at both ends of the upper surface of the oblique anchor short pile foundation, and vertical measuring plates are arranged on both sides of the upper surface of the oblique anchor short pile foundation.

[0006] Among them, the test frame includes two concrete reaction piers and two rectangular main beams, the two rectangular main beams are respectively located below the two ends of the short secondary beams, the concrete reaction piers are arranged between the lower parts of the ends of the two rectangular main beams, the concrete reaction piers are perpendicular to the corresponding rectangular main beams, the reference beam member is located between the upper surfaces of the two concrete reaction piers and parallel to the two rectangular main beams, and the second hydraulic jack is located on one side of one of the concrete reaction piers close to the inclined anchor short pile foundation.

[0007] Wherein, the reference beam component comprises a reference beam body and two reference beam piers, the reference beam body is located between the two concrete reaction piers, and the bottoms of both ends of the reference beam body are provided with the reference beam piers.

[0008] Among them, the rated load-bearing capacity of the first hydraulic jack is 500 tons, and the rated load-bearing capacity of the second hydraulic jack is 100 tons.

[0009] Wherein, a plurality of nut pads are also provided on the upper surface of the perforated box-type secondary beam, and the plurality of nut pads are used to install a plurality of the main reinforcements.

[0010] The present invention also provides a method for testing the pull-out and horizontal load of a short-pile foundation with an inclined anchor, which is applied to the pull-out and horizontal load testing device for a short-pile foundation with an inclined anchor as described above, and comprises the following steps:

[0011] Preliminary preparation: After determining the test site, arrange the test site, install the test system, start the first hydraulic jack and the second hydraulic jack simultaneously, and fully debug the system until it meets the test requirements;

[0012] Test loading: During the test loading process, the vertical load is applied to the surface of the rectangular main beam through the first hydraulic jack and then transferred to the concrete reaction pier. The pull-out force is provided by the connection between the main reinforcement and the inclined anchor short pile foundation. The lateral horizontal load is applied to the concrete reaction pier through the second hydraulic jack. The concrete reaction pier provides a reaction force and acts on the side of the inclined anchor short pile foundation through the force transmission cylinder.

[0013] Data measurement: for the inclined anchor short pile foundation, the pile top displacement, the ground displacement around the pile and the steel bar strain are measured during the field test;

[0014] Data collection: After each level of load is applied, the displacement should be measured at 5 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes respectively, and then measured every 30 minutes;

[0015] Stability standard: Starting from the 30th minute after the graded load is applied, the displacement observation values ​​are calculated three times every 30 minutes for 1.5 hours. The displacement change within one hour does not exceed 0.5mm and occurs twice in succession;

[0016] Termination condition: When the vertical pull load and lateral horizontal load reach the preset conditions, the loading is terminated.

[0017] The present invention discloses a pull-out and horizontal load test device and method for a short-pile foundation of an inclined anchor, comprising a test frame, a short secondary beam, a reference beam member, a perforated box-type secondary beam, a first hydraulic jack, a short-pile foundation of an inclined anchor, a second hydraulic jack and a force transmission cylinder. The device can simultaneously apply pull-out and horizontal loads, thereby more realistically restoring the stress state of the foundation under complex working conditions, effectively breaking through the limitation that the existing test device can only apply a single load, and providing a more reliable and efficient test means for in-depth research on the mechanical properties of the short-pile foundation of an inclined anchor. In addition, by flexibly adjusting key parameters such as foundation size, inclined anchor inclination angle, and anchoring form, the technical solution can systematically analyze the influence of different factors on the stress-deformation characteristics, bearing capacity distribution, and failure mechanism of the short-pile foundation of an inclined anchor in actual working conditions, filling the gap in existing research in this field. This not only provides a solid scientific basis for the design and construction technology optimization of the short-pile foundation of an inclined anchor, but also promotes its wide application in the construction of power transmission lines, and has important theoretical and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a side view of the upper pull-out and horizontal load test device for inclined anchor short pile foundation provided by the present invention.

[0020] Figure 2 It is a top view of the upper pull-out and horizontal load test device for inclined anchor short pile foundation provided by the present invention.

[0021] Figure 3 It is a flow chart of the steps of the upper pull-out and horizontal load test method of the inclined anchor short pile foundation provided by the present invention.

[0022] 1-concrete reaction pier, 2-rectangular main beam, 3-short secondary beam, 4-first hydraulic jack, 5-perforated box secondary beam, 6-second hydraulic jack, 7-force transmission cylinder, 8-reference beam pier, 9-reference beam body, 10-main reinforcement, 11-oblique anchor short pile foundation, 12-nut spacer, 13-horizontal measuring plate, 14-vertical measuring plate. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0024] See also Figure 1 and Figure 2The present invention provides a pull-out and horizontal load test device for an inclined anchor short pile foundation 11, the pull-out and horizontal load test device for the inclined anchor short pile foundation 11 comprises a test frame, a short secondary beam 3, a reference beam component, a perforated box-type secondary beam 5, a first hydraulic jack 4, an inclined anchor short pile foundation 11, a second hydraulic jack 6 and a force transmission cylinder 7, the short secondary beam 3 is transversely installed in the middle of the test frame, the first hydraulic jack 4 is arranged above the short secondary beam 3, the perforated box-type secondary beam 5 is arranged at the output end of the first hydraulic jack 4, the inclined anchor short pile foundation 11 is installed around the perforated box-type secondary beam 5 through a plurality of main bars 10, the inclined The anchor short pile foundation 11 is located below the short secondary beam 3. The test frame is also provided with the second hydraulic jack 6. The output end of the second hydraulic jack 6 is in contact with the end wall of the inclined anchor short pile foundation 11 through the force transmission tube 7. The test frame is also provided with the reference beam component horizontally arranged. The reference beam component is perpendicular to the short secondary beam 3. The reference beam component is located above the inclined anchor short pile foundation 11 and below the short secondary beam 3. Horizontal measuring plates 13 are arranged at both ends of the upper surface of the inclined anchor short pile foundation 11, and vertical measuring plates 14 are arranged on both sides of the upper surface of the inclined anchor short pile foundation 11.

[0025] In this embodiment, the device can simultaneously apply pull-out and horizontal loads, thereby more realistically restoring the stress state of the foundation under complex working conditions, effectively breaking through the limitation that the existing test device can only apply a single load, and providing a more reliable and efficient test method for in-depth research on the mechanical properties of the inclined anchor short pile foundation 11. In addition, by flexibly adjusting key parameters such as foundation size, inclined anchor inclination, and anchoring form, the technical solution can systematically analyze the influence of different factors on the stress-deformation characteristics, bearing capacity distribution, and failure mechanism of the inclined anchor short pile foundation 11 in actual working conditions, filling the gap in existing research in this field. This not only provides a solid scientific basis for the design and construction technology optimization of the inclined anchor short pile foundation 11, but also promotes its wide application in transmission line construction, which has important theoretical and practical significance.

[0026] Furthermore, the test frame includes two concrete reaction piers 1 and two rectangular main beams 2, the two rectangular main beams 2 are respectively located below the two ends of the short secondary beam 3, the concrete reaction piers 1 are arranged between the lower parts of the ends of the two rectangular main beams 2, the concrete reaction piers 1 are perpendicular to the corresponding rectangular main beams 2, the reference beam member is located between the upper surfaces of the two concrete reaction piers 1 and is parallel to the two rectangular main beams 2, and the second hydraulic jack 6 is located on one side of one of the concrete reaction piers 1 close to the inclined anchor short pile foundation 11.

[0027] Furthermore, the reference beam component includes a reference beam body 9 and two reference beam piers 8 . The reference beam body 9 is located between the two concrete reaction piers 1 . The reference beam piers 8 are provided at the bottom of both ends of the reference beam body 9 .

[0028] Furthermore, the rated load-bearing capacity of the first hydraulic jack 4 is 500 tons, and the rated load-bearing capacity of the second hydraulic jack 6 is 100 tons.

[0029] Furthermore, a plurality of nut spacers 12 are provided on the upper surface of the perforated box-type secondary beam 5 , and the plurality of nut spacers 12 are used to install the plurality of main reinforcements 10 .

[0030] Furthermore, the inclined anchor short pile foundation 11 is composed of a short pile (1m in diameter, 2m in length) and three inclined anchors (130mm in diameter, 3.5m in length), the three inclined anchors are evenly arranged at intervals of 120° on the horizontal plane, the angle between the pile body and the anchor rod is 30°, the connection node between the short pile and the anchor rod is located 0.7m below the ground, and the anchor bar at the node is anchored by an anchor plate. Longitudinal steel bars are arranged inside the short pile, with a reinforcement ratio of 0.6%, HPB300 stirrups with a diameter of 10mm, spirally arranged, and C30 commercial concrete is used for concrete; the inclined anchor rod is composed of anchor bars and fine-grained concrete, with a reinforcement ratio of 8.6%, the anchor bars are made of three 25mm HRB400 hot-rolled ribbed steel bars, the anchor plate is made of a steel plate with a diameter of 140mm and a thickness of 40mm, and the connection between the steel bar and the anchor plate is through-hole plug welding.

[0031] See also Figure 3 The present invention also provides a method for testing the pull-out and horizontal load of an inclined anchor short pile foundation 11, which is applied to the pull-out and horizontal load testing device for the inclined anchor short pile foundation 11 as described above, and comprises the following steps:

[0032] S1. Preliminary preparation: After determining the test site, arrange the test site, install the test system, start the first hydraulic jack 4 and the second hydraulic jack 6 simultaneously, and fully debug the system until it meets the test requirements;

[0033] S2, test loading: During the test loading process, the vertical load is transferred to the concrete reaction pier 1 by the first hydraulic jack 4 acting on the surface of the rectangular main beam 2, and the pull-out force is provided by the connection between the main reinforcement 10 and the inclined anchor short pile foundation 11. The lateral horizontal load is applied by the second hydraulic jack 6 acting on the concrete reaction pier 1, and the concrete reaction pier 1 provides a reaction force, which acts on the side of the inclined anchor short pile foundation 11 through the force transmission cylinder 7;

[0034] S3, data measurement: measuring the pile top displacement, the ground displacement around the pile and the steel bar strain during the field test of the inclined anchor short pile foundation 11;

[0035] S4. Data collection: After each level of load is applied, the displacement should be measured at 5 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes respectively, and then measured every 30 minutes;

[0036] S5. Stability standard: Starting from the 30th minute after the graded load is applied, the displacement observation values ​​are calculated three times every 30 minutes for 1.5 hours. The displacement change within one hour does not exceed 0.5mm and occurs twice in succession;

[0037] S6. Termination condition: When the vertical pull load and lateral horizontal load reach the preset conditions, the loading is terminated.

[0038] Furthermore, the specific contents of the preliminary preparation include: after determining the test site, the test site is arranged, and the site conditions are as similar as possible to avoid errors caused by differences in geological conditions. In this pull-out + horizontal load field test, a reaction pier is set to provide reaction force during pull-out. The main reinforcement 10 of the test foundation extends 2.5m out of the ground surface and is connected to the perforated box-type secondary beam 5 through a nut to ensure the transmission of the pull-out load. Considering the on-site geological conditions and the test load, the cast-in-place concrete reaction pier 1 penetrates more than 0.3m into the bedrock. The pull-out load is applied to the perforated box-type secondary beam 5 to the main reinforcement 10 through the calibrated first hydraulic jack 4. The reaction force transmission order is: the short secondary beam 3, the rectangular main beam 2, the concrete reaction pier 1 and the bedrock. The horizontal load directly relies on the concrete reaction pier 1 to provide reaction force, and acts on the side of the inclined anchor short pile foundation 11 through the force transmission cylinder 7. After installing the test system, the first hydraulic jack 4 and the second hydraulic jack 6 are started synchronously, and the system is fully debugged until it meets the test requirements. During debugging, the pre-pressure of the first hydraulic jack 4 and the second hydraulic jack 6 shall not exceed the first level load value.

[0039] Furthermore, the specific contents of the test loading include: during the test loading process, after the vertical load is transferred to the concrete reaction pier 1 through the first hydraulic jack 4 acting on the surface of the rectangular main beam 2, the pull-out force is provided by relying on the connection between the main reinforcement 10 and the inclined anchor short pile foundation 11; the lateral horizontal load is applied to the concrete reaction pier 1 through the second hydraulic jack, and the vertical pull-out load and the lateral horizontal load are loaded alternately, and the slow maintenance load method is adopted, that is, loading step by step, and the next level of load is added after each level of load reaches relative stability until the test pile is destroyed. When loading equally step by step, each level of load takes 1 / 10 of the maximum test load value, among which the first level loading amount can be twice the graded load, and the unloading is also carried out in stages, using step-by-step equal unloading, and each level of unloading takes twice the graded load during loading, and the same level of load is alternately added and unloaded in the vertical-horizontal order. The load should be transferred evenly, continuously and without impact during loading and unloading, and the variation range of each level of load during the maintenance process shall not exceed 10% of the graded load.

[0040] Furthermore, the specific content of the data measurement mainly measured the pile top displacement, ground displacement around the pile and steel bar strain during the field test of the inclined anchor short pile foundation 11:

[0041] ① Displacement measurement: the reference beam body 9 is installed above the reference beam pier 8, parallel to the rectangular main beam 2, the displacement meter base is symmetrically arranged on the reference beam body 9, the top pin is located on the vertical measurement plate, and the vertical measurement plate is rigidly connected to the inclined anchor short pile foundation 11 through steel bars, wherein the two vertical measurement plates are parallel to the top surface of the inclined anchor short pile foundation 11, and are used to measure the vertical displacement of the inclined anchor short pile foundation 11; the two horizontal measurement plates 13 are perpendicular to the top surface of the short pile, and are used to monitor the horizontal displacement of the inclined anchor short pile foundation 11; the remaining measurement plates are arranged around the foundation, parallel to the ground, and are used to monitor the displacement of the ground around the pile.

[0042] ②Rebar strain measurement: The strain of anchor reinforcement and pile longitudinal reinforcement is measured by a reinforcement stress gauge with an accuracy of 0.01MPa. Before casting the specimen, reinforcement stress gauges need to be arranged at the corresponding positions to record the strain response of the longitudinal reinforcement and anchor reinforcement at all times. Among them, stress gauges are installed on the longitudinal reinforcement at intervals of 0.5m to measure the axial force of the short pile; a reinforcement stress gauge is installed on one of the anchor bars at a distance of 0.2m from the pile anchor node, and the following reinforcement stress gauges are installed at intervals of 0.5m to monitor the axial force of the inclined anchor.

[0043] Furthermore, the specific contents of data collection include: after each level of load is applied, the displacement should be measured at 5min, 15min, 30min, 45min, and 60min, and then every 30min. When unloading, each level of load is maintained for 1h, and after the displacement is measured at 15min, 30min, and 60min, the next level of load can be unloaded. After unloading to zero, the residual displacement should be measured, and the maintenance time shall not be less than 3h. The measurement time is at 15min and 30min, and then every 30min. The residual displacement is measured. Each measurement value is recorded in the test record sheet. The settlement of each level of load can be obtained by the weighted average method according to the actual measurement value of each percentage meter.

[0044] Furthermore, the specific contents of the stability standard include: starting from the 30th minute after the graded load is applied, the displacement observation values ​​are calculated every 30 minutes for three consecutive times within 1.5 hours. The displacement change within one hour shall not exceed 0.5mm and shall occur twice in succession.

[0045] Furthermore, the specific contents of the termination conditions include:

[0046] 1) For vertical pull-out load, loading can be terminated when one of the following situations occurs:

[0047] ① Under a certain level of load, the uplift of the pile top is 5 times greater than the uplift under the previous level of load;

[0048] ②Control by the uplift amount of the pile top. When the cumulative uplift amount of the pile top exceeds 100mm;

[0049] ③ According to the tensile strength of the steel bar, the pull-out load on the pile top reaches 0.9 times the standard value of the steel bar strength.

[0050] 2) When the lateral horizontal load is applied, the loading can be terminated when one of the following situations occurs:

[0051] ①The pile body is broken;

[0052] ②The horizontal displacement exceeds 30-40 mm;

[0053] ③The horizontal displacement reaches the allowable value of horizontal displacement required by the design.

[0054] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A device for testing the pull-out and horizontal load of inclined anchor short pile foundation, characterized in that: The invention comprises a test frame, a short secondary beam, a reference beam component, a perforated box-type secondary beam, a first hydraulic jack, an inclined anchor short pile foundation, a second hydraulic jack and a force transmission cylinder, wherein the short secondary beam is transversely installed in the middle of the test frame, the first hydraulic jack is arranged above the short secondary beam, the perforated box-type secondary beam is arranged at the output end of the first hydraulic jack, the inclined anchor short pile foundation is installed around the perforated box-type secondary beam through a plurality of main bars, the inclined anchor short pile foundation is located below the short secondary beam, and the test frame is also provided with a plurality of main bars. The second hydraulic jack is provided, and the output end of the second hydraulic jack is abutted against the end wall of the inclined anchor short pile foundation through the force transmission cylinder. The test frame is also provided with the reference beam component horizontally arranged, and the reference beam component is perpendicular to the short secondary beam. The reference beam component is located above the inclined anchor short pile foundation and below the short secondary beam. Horizontal measuring plates are provided at both ends of the upper surface of the inclined anchor short pile foundation, and vertical measuring plates are provided on both sides of the upper surface of the inclined anchor short pile foundation.

2. The inclined anchor short pile foundation pull-out and horizontal load test device according to claim 1, characterized in that: The test frame includes two concrete reaction piers and two rectangular main beams, the two rectangular main beams are respectively located below the two ends of the short secondary beam, the concrete reaction piers are arranged between the lower parts of the ends of the two rectangular main beams, the concrete reaction piers are perpendicular to the corresponding rectangular main beams, the reference beam member is located between the upper surfaces of the two concrete reaction piers and parallel to the two rectangular main beams, and the second hydraulic jack is located on one side of one of the concrete reaction piers close to the inclined anchor short pile foundation.

3. The inclined anchor short pile foundation pull-out and horizontal load test device according to claim 2, characterized in that: The reference beam component comprises a reference beam body and two reference beam piers. The reference beam body is located between the two concrete reaction piers. The bottoms of both ends of the reference beam body are provided with the reference beam piers.

4. The inclined anchor short pile foundation pull-out and horizontal load test device according to claim 3, characterized in that: The rated load-bearing capacity of the first hydraulic jack is 500 tons, and the rated load-bearing capacity of the second hydraulic jack is 100 tons.

5. The inclined anchor short pile foundation pull-out and horizontal load test device according to claim 4, characterized in that: The upper surface of the perforated box-type secondary beam is also provided with a plurality of nut spacers, and the plurality of nut spacers are used to install a plurality of main reinforcements.

6. A method for testing the pull-out and horizontal load of a short-pile foundation with an inclined anchor, applied to the pull-out and horizontal load testing device for a short-pile foundation with an inclined anchor as claimed in claim 5, characterized in that: The steps include: Preliminary preparation: After determining the test site, arrange the test site, install the test system, start the first hydraulic jack and the second hydraulic jack simultaneously, and fully debug the system until it meets the test requirements; Test loading: During the test loading process, the vertical load is applied to the surface of the rectangular main beam through the first hydraulic jack and then transferred to the concrete reaction pier. The pull-out force is provided by the connection between the main reinforcement and the inclined anchor short pile foundation. The lateral horizontal load is applied to the concrete reaction pier through the second hydraulic jack. The concrete reaction pier provides a reaction force and acts on the side of the inclined anchor short pile foundation through the force transmission cylinder. Data measurement: for the inclined anchor short pile foundation, the pile top displacement, the ground displacement around the pile and the steel bar strain are measured during the field test; Data collection: After each level of load is applied, the displacement should be measured at 5 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes respectively, and then measured every 30 minutes; Stability standard: Starting from the 30th minute after the graded load is applied, the displacement observation values ​​are calculated three times every 30 minutes for 1.5 hours. The displacement change within one hour does not exceed 0.5mm and occurs twice in succession; Termination condition: When the vertical pull load and lateral horizontal load reach the preset conditions, the loading is terminated.

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