Testing device for pile horizontal loading model test

Abstract

The utility model belongs to the technical field of pile load tests, and discloses a test device for a pile horizontal loading model test, in the test device for the pile horizontal loading model test, a rigid steel pipe pile is pre-buried in sandy soil, and the burying depth is about 55cm; the rigid steel pipe pile is sleeved with an adjustable iron ring, the adjustable iron ring is in bolted connection with a steel strand, the steel strand winds around the pulley, and a tray is installed at the end of the steel strand; the pulley is installed on the pulley support, and the pulley support is fixed on the model box. According to the utility model, the weight is lightly held and placed during test loading and unloading, so that impact load is avoided; during loading and unloading, the centers of the weights should be kept on the same vertical line, and stable load holding is ensured. According to the utility model, eccentric loading can be avoided, so that the pile is subjected to oblique tension; and meanwhile, data distortion caused by oblique installation of the dial indicator in the horizontal and vertical directions can be avoided. The experiment result is reasonable, the precision requirement is met, and the larger requirement for measuring the rock-soil stress is met.

Description

Technical Field

[0001] The utility model belongs to the technical field of pile load testing, in particular to a pile horizontal loading model test device. Background Art

[0002] Currently, under the action of lateral loads on the pile top, the pile body experiences horizontal displacement and rotation. The soil in front of the pile is subjected to lateral compression and reacts with a horizontal reaction force on the pile body. The magnitude of this force is primarily related to the horizontal displacement of the pile body in the compressed soil and the horizontal reaction coefficient at that location. Depending on the relative stiffness of the pile and the soil, single piles exhibit two distinct failure modes: rigid piles fail due to rotation or translation, and elastic long piles fail due to deflection. When the pile top is free and the pile is not deeply embedded in the soil, a rigid pile subjected to horizontal forces will rotate about a point on the pile axis like a rigid body, without considering the deflection of the pile body. Calculations of various points on the pile body require only the position of the rotation point and the horizontal displacement of any point on the pile body other than the rotation point. However, the deflection of elastic long piles is much more complex, requiring strain gauges attached to the pile surface to calculate the bending moment and rotation angle, and then performing multiple integration and differentiation operations to determine the deflection. Quantities related to the horizontal reaction coefficient of the soil at that location can be obtained through T-bar tests. If a rigid pile is used for static load testing, the pile displacement can be further determined. However, during existing horizontal loading model tests, the center of gravity of the model pile is prone to shifting, causing sway.

[0003] Through the above analysis, the problems and defects of the existing technology are: during the existing pile horizontal loading model test, the center of gravity of the model pile is prone to change, resulting in shaking. Utility Model Content

[0004] In view of the problems existing in the prior art, the utility model provides a pile horizontal loading model test device.

[0005] The utility model is implemented as follows: a pile horizontal loading model test device, the device includes a rigid steel pipe pile, the rigid steel pipe pile is pre-buried in sand, and the burial depth is about 55 cm; an adjustable iron ring is sleeved on the rigid steel pipe pile, the iron ring is bolted with a steel strand, the steel strand is passed around a pulley, a tray is installed at the end of the steel strand, the pulley is installed on a pulley bracket, and the pulley bracket is fixed on the sand model box.

[0006] Furthermore, the pulley bracket is installed at an appropriate position of the model box, and the center of the pulley is aligned with the center of the pile body cross section to ensure that the steel strand acts on the center position of the pile body through the pulley during loading.

[0007] Furthermore, a meter stand and two dial indicators are provided on the other side of the model box. The dial indicators are in horizontal contact with the pile body, and the extension lines of the dial indicators pass through the center of the pile body cross section, which are used to measure the horizontal displacement of the pile during loading.

[0008] Furthermore, the tray is used to place weights during loading, and the weights are loaded in equal amounts step by step. After each level of load is applied, the horizontal displacement is measured at a certain time interval until the horizontal displacement change reaches a relatively stable standard, and then the next level of load is applied.

[0009] The utility model fixes the model pile with a clamp to prevent it from shaking; the burial depth of 55 cm is selected to avoid the boundary effect of the model box (the model pile needs to be greater than 5D (20 cm) from the bottom. According to the results of the CPT test, the artificial sand rain method can form a relatively homogeneous soil. When the total thickness of the sand is 80 cm, the soil from the soil surface to 60 cm below the soil surface can be ensured to be approximately uniform; the pile end is blocked with paper strips to better simulate closed steel piles, and lightweight materials are used to avoid the addition of blocking materials to change the pile stiffness and center of gravity.

[0010] The utility model installs a pulley bracket and a pulley at an appropriate position on the side of the model box so that the center of the pulley is opposite to the center of the pile cross section. In order to avoid the influence of loading on the measurement, a meter stand and two 50mm scale dial indicators are installed on the other side of the model box so that the two meter needles touch the pile body horizontally and the extension lines pass through the center of the pile cross section. The utility model can avoid eccentric loading, which causes the pile to be subjected to oblique tension; at the same time, it can avoid oblique installation of the dial indicator in the horizontal and vertical directions, which causes data distortion; the purpose of installing two dial indicators is to calculate the inclination of the pile by measuring the displacement value and distance of two points along the vertical direction of the pile body, and the position of the rotation point and the displacement of any point along the pile body can be calculated by the inclination angle and the displacement of one of the two points.

[0011] Install an iron ring at the same height as the pile and the upper edge of the pulley, and pass a steel strand with a diameter of 1.5mm through the iron ring. Properly adjust the position of the iron ring so that when the steel strand is stressed, its extension line passes through the center of the iron ring and the pile to avoid eccentric tension. Add a tray to the other end of the steel strand for loading. The loading is carried out in stages, using weights to load the load in equal amounts step by step; because the specifications stipulate that the graded load should be taken as the maximum load or 1 / 10 of the estimated ultimate bearing capacity, it is determined by pre-loading that 1.275kg is used as the graded load. To avoid impact loads, the weights should be handled with care during the test loading and unloading; to ensure stable load holding, the center of the weights should be kept on the same vertical line during loading and unloading. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of a pile horizontal loading model test device provided by an embodiment of the utility model.

[0013] Figure 2It is a schematic diagram of the structure of an adjustable iron ring and steel strand provided by an embodiment of the utility model.

[0014] Figure 3 This is a schematic diagram of the first test loading provided by an embodiment of the present utility model.

[0015] Figure 4 This is a schematic diagram of the second test loading provided by an embodiment of the present utility model.

[0016] Figure 5 It is a schematic diagram of the horizontal force-force application point displacement (H0-Y0) relationship curve of the first static load test provided by an embodiment of the present utility model.

[0017] Figure 6 It is a schematic diagram of the horizontal force-force application point displacement (H0-Y0) relationship curve of the second static load test provided by an embodiment of the present utility model.

[0018] Figure 7 This is a comparison diagram of the horizontal force-force application point displacement (H0-Y0) relationship curves during two static load tests provided by an embodiment of the present utility model.

[0019] Figure 8 It is a comparison diagram of horizontal force-force application point displacement gradient (H0-△Y0 / △H0) curves of two static load tests provided by the embodiment of the present utility model.

[0020] Figure 9 It is a schematic diagram of the horizontal displacement distribution curve of the pile body in the first static load test provided by an embodiment of the present utility model.

[0021] Figure 10 It is a schematic diagram of the horizontal displacement distribution curve of the pile body in the second static load test provided by an embodiment of the present utility model.

[0022] In the figure: 1. Sand; 2. Lower dial indicator; 3. Upper dial indicator; 4. Rigid steel pipe pile; 5. Pulley bracket; 6. Pulley; 7. Tray; 8. Adjustable iron ring; 9. Steel strand. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] In view of the problems existing in the prior art, the present invention provides a pile horizontal loading model test device, which is described in detail below with reference to the accompanying drawings.

[0025] Ordinary technicians in the industry can also use other steps to implement the pile horizontal loading model test device provided by the utility model. Figure 1 The pile horizontal loading model test device provided by the present invention is only a specific embodiment.

[0026] like Figure 1-Figure 2 As shown, the pile horizontal loading model test apparatus provided by the present invention comprises a rigid steel pipe pile 4 pre-buried in sand at a depth of approximately 55 cm. An adjustable iron ring 8 is sleeved onto the rigid steel pipe pile 4, to which a steel strand 9 is bolted. The steel strand 9 is passed through a pulley 6, with a tray mounted on the end. The pulley 6 is mounted on a pulley bracket 5, which is fixed to the model box.

[0027] This utility model primarily targets rigid steel pipe piles, a typical example of rigid piles. Therefore, the static load test utilizes a steel pipe as a model pile, pre-buried in sand at a depth of approximately 55 cm. Horizontal loads are applied using the weight of weights, transmitted via pulleys, steel strands, and iron rings fixed to the pile body. Horizontal displacement is measured using two 50 mm range dial indicators. A preliminary test is required before the static load test to determine the ultimate horizontal bearing capacity of a single pile at this depth.

[0028] The method for using the device provided in the embodiment of the present utility model includes:

[0029] S101: Fill the model box with sand to the bottom of the model pile, pre-embed the model pile, and then fill the model box with sand to the top;

[0030] S102: Install a pulley bracket and a pulley at an appropriate position on the side of the model box so that the center of the pulley is aligned with the center of the pile cross section; install a meter stand and two dial indicators on the other side of the model box so that the two dial needles touch the pile horizontally and the extension lines pass through the center of the pile cross section.

[0031] S103: Install an iron ring at the same height as the pile and the upper edge of the pulley, and pass the steel strand through the iron ring; properly adjust the position of the iron ring so that when the steel strand is stressed, its extension line passes through the center of the iron ring and the pile; after the adjustment is completed, fix the iron ring and place the steel strand on the pulley; and use a ruler to measure the distance between the iron ring and the upper dial indicator, the upper dial indicator and the lower dial indicator, and the lower dial indicator and the soil surface.

[0032] S104: Add a tray to the other end of the steel strand and apply loading; the loading is carried out in stages, using weights to apply equal amounts at each stage; after each stage of load is applied, the horizontal displacement is measured at regular time intervals until the horizontal displacement within a certain time period does not exceed a certain range for two consecutive times; when the horizontal displacement change reaches a relatively stable standard, the next stage of load is applied.

[0033] S105: According to the applied load, choose to terminate loading and prepare for unloading; when preparing to unload, proceed in stages; after unloading to 0, repeat the test and conduct another parallel test.

[0034] In S101 provided in the embodiment of the present invention, the specific process of pre-embedded model piles is as follows:

[0035] Fill the model box with sand to the bottom of the model pile, pre-embed the model pile, and then fill the sand to the top of the model box so that the burial depth is 55 cm when the sand fills the model box; when pre-embedding, use paper foam or other lightweight objects to block the bottom of the pile, and fix the model pile with a clamp.

[0036] The sandy soil used in the T-bar test was the same as that used in the test. The sandy soil layer was prepared by the same artificial sand rain method as in the test preparation stage until the sandy soil filled the model box. At this time, the total thickness of the soil layer was the height of the model box, i.e. 80 cm.

[0037] In S102 provided in the embodiment of the present utility model, the measuring range of the two dial indicators is 50 mm.

[0038] In S104 provided by the embodiment of the present invention, the specific process of using weights to load the weights step by step is as follows:

[0039] Add a tray at the other end of the steel strand for loading; the loading is carried out in stages, using weights to load the load in equal amounts step by step; the specification stipulates that the graded load should be taken as the maximum load or 1 / 10 of the estimated ultimate bearing capacity, and after pre-loading, it is determined that 1.275kg is used as the graded load; the weights should be handled with care during the loading and unloading test, and the center of the weight circle should be kept on the same vertical line during loading and unloading.

[0040] In S104 provided by the embodiment of the present invention, the specific process of measuring the horizontal displacement at a certain time interval after each level of load is applied is as follows:

[0041] After each level of load is applied, the horizontal displacement is measured at 1, 2, 3, 4, and 5 minutes, and then measured every 2 minutes until the horizontal displacement does not exceed 0.1 mm for two consecutive times within 2 minutes. Starting from the 5th minute after the graded load is applied, the displacement is calculated based on three consecutive 2-minute observations for 6 minutes. When the horizontal displacement change reaches the relatively stable standard, the next level of load is applied.

[0042] In S105 provided by the embodiment of the present invention, the specific process of selecting to terminate loading and prepare for unloading according to the applied load is as follows:

[0043] When one of the following situations occurs, loading can be terminated and unloading can be prepared: under a certain level of load, the horizontal displacement is greater than 5 times the displacement under the previous level of load, and the total horizontal displacement exceeds 40mm; under a certain level of load, the horizontal displacement is greater than 2 times the displacement value under the previous level of load, and has not reached the relative stability standard after 6 minutes; the total load has reached the maximum load required by the design or the total displacement value has reached the design requirements.

[0044] In S105 provided by the embodiment of the present invention, the specific process of performing the unloading stage is as follows:

[0045] The unloading amount for each level is twice the graded load during loading according to the specification, and the load is unloaded in equal amounts step by step; each level of load is maintained for 4 minutes, and the horizontal displacement is measured at 1, 2, and 4 minutes, and then the load of one level can be unloaded; after unloading to zero, the residual displacement should be measured, and the maintenance time is 6 minutes, and the measurement time is 1 and 2 minutes, and then it is measured every 2 minutes.

[0046] The technical solution of the present utility model will be further described below in conjunction with specific embodiments.

[0047] 1. Selection of model piles

[0048] Because this test used a T-type probe to simulate a pile section placed horizontally in the soil, to avoid size effects, a steel pipe with the same diameter as the T-type probe was selected for the model pile test. To simplify calculations and ensure the pile was rigid during the test, the wall thickness of the steel pipe was carefully selected. To ensure consistency with the T-bar test results and to avoid boundary effects in the model box, the pile was buried at a depth of approximately 55 cm during the static load test.

[0049] The steel pipe used in the test has a wall thickness of 2mm, an outer diameter of 40mm, and a length of 1000mm. The elastic modulus of the steel pipe is taken as 210GPa, and the moment of inertia I of the annular section of the steel pipe is used to calculate the bending stiffness of the pile body. According to the content of "Soil Mechanics and Foundation Engineering", single piles buried in the soil under horizontal load can be divided into three types according to the converted burial depth αL: elastic long piles, medium-long piles and rigid piles. It is necessary to first calculate the stiffness of the three types of steel pipes under horizontal load in sand. αL<2.5 is a rigid pile, αL≥4.0 is an elastic long pile, and piles between the two are medium-long piles. In the converted burial depth αL, L is the depth of the pile into the soil, and α is the horizontal deformation coefficient of the pile. The calculation formula for α is:

[0050]

[0051] Where: m - proportional coefficient of horizontal reaction coefficient, unit MN / m 4 , look up the coefficient table, for medium-dense sand, the value can be 10 to 22, here we take the maximum value of 22 for conservative calculation;

[0052] EI——Bending stiffness of pile body, unit kN·m 2 ;

[0053] b0 is the calculated width considering the spatial stress of the soil around the pile. For circular cross-section piles with a diameter D less than 1m, it can be taken as 0.9(1.5D+0.5), unit: m.

[0054] The final calculation results are shown in Table 1.

[0055] Table 1 Model pile parameters

[0056] Diameter D / cm Pipe wall thickness / mm <![CDATA[EI / kN·m 2 ]]> <![CDATA[b0 / m]]> αL 4.000 2.000 9.1 0.504 2.3

[0057] The calculation results show that when the buried depth of the model pile used in the static load test is 0.55m, the converted buried depth αL is less than 2.5, and the pile selected for the test is a rigid pile.

[0058] 2. Experimental plan

[0059] According to the Technical Specifications for Testing of Building Foundation Pile (JGJ106-2014), the commonly used static load tests for single piles are unidirectional multi-cycle loading method and slow-maintained loading method. The unidirectional multi-cycle loading method shortens the time it takes for the soil to reach final deformation by multi-cycle loading and unloading, while the slow-maintained loading method can obtain more accurate deformation than the unidirectional multi-cycle loading method by increasing the load in sequence. This test selected the slow-maintained loading method for the static load test of single piles. On the one hand, this is because the static load test needs to obtain more accurate values; on the other hand, this is because the slow-maintained loading method loads through fixed graded loads, which is very similar to the process of the probe penetrating under different stresses in the T-bar stress control. However, the unidirectional multi-cycle loading method is somewhat different from the unidirectional penetration in the stress control due to the back-and-forth cycle.

[0060] The test plan of the slow sustained load method for this test is as follows:

[0061] 1) Fill the model box with sand to the bottom of the model pile, pre-embed the model pile, and then fill the model box with sand to the top, so that the burial depth is 55cm when the sand fills the model box. When pre-embedding, you need to block the bottom of the pile with paper strips, foam, or other lightweight objects, and secure the model pile with a clamp to prevent it from shaking.

[0062] 2) Use the same sand and soil as in the T-bar test and the same artificial sand rain method as in the test preparation stage to prepare the sand layer until the sand fills the model box. At this time, the total thickness of the soil layer is the height of the model box, that is, 80 cm.

[0063] 3) Install the pulley bracket and pulley at an appropriate position on the side of the model box, with the pulley center facing the center of the pile cross section. To avoid the influence of loading on the measurement, install the meter stand and two 50mm range dial indicators on the other side of the model box, with the needles of the two indicators horizontally touching the pile body and the extension lines passing through the center of the pile cross section.

[0064] 4) Install an iron ring at the same height as the pile and the pulley, and pass a 1.5mm diameter steel strand through the ring. Adjust the ring so that when the strand is stressed, its extension passes exactly through the center of the ring and the pile to avoid eccentric tension. After adjustment, secure the ring and place the strand on the pulley. Use a ruler to measure the distance between the ring and the upper dial indicator (hereinafter referred to as the upper indicator), the upper indicator and the lower dial indicator (hereinafter referred to as the lower indicator), and the lower indicator and the soil surface.

[0065] 5) Add a tray to the other end of the strand and apply the load. Loading is performed in stages, using weights to apply equal amounts at each stage. Since the specification stipulates that the graded load should be 1 / 10 of the maximum load or estimated ultimate bearing capacity, a graded load of 1.275 kg was determined after preloading. To avoid impact loads, the weights should be handled with care during loading and unloading. To ensure stable load holding, the centers of the weights should be aligned vertically during loading and unloading.

[0066] 6) After each level of load is applied, measure the horizontal displacement at 1, 2, 3, 4, and 5 minutes, and then measure it every 2 minutes thereafter. This is done until the horizontal displacement does not exceed 0.1 mm for two consecutive 2-minute periods (starting from the 5th minute after the graded load is applied, and calculated based on three consecutive 2-minute displacement observations for 6 minutes). When the horizontal displacement reaches a relatively stable standard, apply the next level of load.

[0067] 7) When one of the following situations occurs, loading can be terminated and unloading can be prepared: under a certain level of load, the horizontal displacement is greater than 5 times the displacement under the previous level of load, and the total horizontal displacement exceeds 40mm; under a certain level of load, the horizontal displacement is greater than 2 times the displacement value under the previous level of load, and has not reached the relative stability standard after 6 minutes; the total load has reached the maximum load required by the design or the total displacement value has reached the design requirements.

[0068] 8) Unloading is carried out in stages, with the unloading amount for each stage being twice the loading stage load (2.55 kg) as per the specification. Unload the load in equal amounts at each stage. Maintain each load stage for 4 minutes. After measuring the horizontal displacement at the 1st, 2nd, and 4th minute mark, the next load stage can be removed. After unloading to zero, measure the residual displacement. This should be maintained for 6 minutes, with measurements taken at the 1st and 2nd minute marks, and every 2 minutes thereafter.

[0069] 9) After unloading to 0, repeat the test and conduct another parallel test.

[0070] Note: In test 1), the burial depth of 55 cm was selected to avoid the boundary effect of the model box (the distance between the model pile and the bottom needs to be greater than 5D (20 cm). According to the results of the CPT test, the artificial sand rain method can form a relatively homogeneous soil. When the total thickness of the sand is 80 cm, the soil from the soil surface to 60 cm below the soil surface can be guaranteed to be approximately uniform. The use of paper strips to block the pile end is to better simulate the closed steel pile. The use of lightweight materials is to avoid the addition of plugging materials to change the pile stiffness and center of gravity.

[0071] The purpose of steps 3) and 4) in the test plan is to avoid eccentric loading, which would subject the pile to oblique tension; at the same time, to avoid oblique installation of the dial indicators in the horizontal and vertical directions, which would distort the data. The purpose of installing two dial indicators is to calculate the inclination angle of the pile by measuring the displacement values ​​and the distance between two points along the vertical direction of the pile body. The position of the rotation point and the displacement of any point along the pile body can be calculated by the inclination angle and the displacement of one of the two points.

[0072] The loading weights in test 5) are the loading weights of the consolidation test, with three types of weights selected: 1.275 kg, 2.55 kg, and 5.1 kg. All weights are weighed with a scale with an accuracy of 0.1 g before the test. The maximum weight deviation is ±10 g, which is less than 1% of the graded load, in accordance with the specification that the load variation range of each grade shall not exceed ±10% of the graded load, and its influence can be ignored. The general format of the test plan table used in the test is shown in Table 2.

[0073] Table 2 Slow maintained load method test plan

[0074] Load (kg) Unloaded (kg) <![CDATA[0、1.275、2.550、3.825……、m max ]]> <![CDATA[m max -2.550、m max -5.110、……、0]]>

[0075] Note: m max Indicates the maximum load.

[0076] The test loading diagram of the two static load tests is shown in Figure 3 、 Figure 4 shown.

[0077] The processing and parameters of some instruments used in the experiment are shown in Table 3.

[0078] Table 3 Static load test equipment parameters

[0079] pulley The maximum load is 200kg. Apply lubricating oil to the bearings before use to reduce friction. Steel strand Maximum load-bearing capacity: 100kg, weight per 10m: 200.5g tray Diameter 8cm, weight 82.3g

[0080] 3. Horizontally loaded pile model test results

[0081] Although the horizontal force on the pile in this test includes the weight of the steel strand below the pulley and the pallet, the suspended steel strand was measured to be approximately 40 cm long and weighing approximately 8 g, and the pallet weighed 82.3 g, for a total weight of 91.3 g. This represents less than 0.5% of the total load of 20.4 kg and is therefore negligible.

[0082] In the test, the pile was buried at a depth of 55 cm and the cantilever end was 45 cm. However, the horizontal load was applied not at the cantilever tip but in the middle. Considering that most piles are subjected to horizontal loads at the pile tip, this test considered the point where the horizontal force was applied (at the iron ring) to be the actual pile tip, rather than the cantilever tip. This served as the basis for the next step in data processing.

[0083] 3.1. Horizontal force-force point displacement (H0-Y0) relationship curve

[0084] According to the above test scheme, the load is loaded and the horizontal force-force point displacement (H0-Y0) relationship curve is obtained as follows: Figure 5-Figure 6 shown.

[0085] The horizontal force-force point displacement (H0-Y0) curves from the two static load tests reveal that during loading, two identical inflection points appeared in the H0-Y0 curves for both static load tests. The first inflection point's abscissa is 89.25 N, and the second inflection point's abscissa is 153.00 N. During unloading, the elastic deformation at the point of application decreases with increasing unloading, and plastic deformation is clearly observed when unloading reaches zero. The appearance of these two inflection points during loading is consistent with the knowledge learned and the specifications, demonstrating the favorable results of the static load tests and the success of the parallel static load test.

[0086] According to the "Technical Specification for Testing of Building Foundation Pile Foundations" (JGJ106-2014), for piles loaded using the slow sustained load method, the horizontal critical load of a single pile is the horizontal load value immediately preceding the first inflection point of the horizontal force-force application point displacement (H0-Y0) relationship curve. The horizontal ultimate bearing capacity of a single pile is the horizontal load value corresponding to the starting point of a significant decrease in the H0-Y0 curve. Therefore, the horizontal critical load of a single pile in the static load test is 76.50 N, and the horizontal ultimate bearing capacity of a single pile is 153.00 N.

[0087] In order to more intuitively compare the pile-soil interaction during the two loadings, the horizontal force-force point displacement (H0-Y0) relationship curves during the two static load tests are compared, as shown in Figure 2. Figure 7 shown.

[0088] Comparing the horizontal force-force-application-point displacement (H0-Y0) curves from the two static load tests reveals that the data points from the two tests overlap in most areas, with a few points not overlapping but with minimal deviation. The H0-Y0 curves from the two tests show similar trends, consisting of roughly three segments with two nearly identical inflection points: one at 89.25 N and the other at 153.00 N. This further demonstrates the effectiveness of the parallel static load tests.

[0089] In summary, according to the horizontal force-force application point displacement (H0-Y0) relationship curve of the static load test and relevant specifications, it can be obtained that under the static load test conditions used in this experiment, the horizontal critical load of a single pile is 76.50N, and the horizontal ultimate bearing capacity of a single pile is 153.00N.

[0090] 3.2 Horizontal force-force point displacement gradient (H0-△Y0 / △H0) relationship curve

[0091] On the basis of the H0-Y0 relationship curve, the displacement increment is divided by the load increment to obtain the displacement gradient, and the horizontal force-force point displacement gradient (H0-△Y0 / △H0) relationship curve of the static load test is obtained, as shown in Figure 8 shown.

[0092] From the comparison of the horizontal force-force application point displacement gradient (H0-△Y0 / △H0) curves of the two static load tests, it can be seen that: although some points in the results obtained from the two tests are relatively discrete, most points are still relatively evenly distributed near the trend line; the H0-△Y0 / △H0 curves obtained from the two static load tests also have two identical inflection points, the abscissa of the first inflection point is 76.50N, and the abscissa of the second inflection point is 153.00N.

[0093] According to the specifications, the horizontal force at the first inflection point corresponds to the horizontal critical load of the single pile, while the second corresponds to the horizontal ultimate bearing capacity of the single pile. From the figure, we can see that the horizontal critical load of the single pile is 76.50 N, and the horizontal ultimate bearing capacity of the single pile is 153.00 N. This is consistent with the previous results.

[0094] In summary, based on the horizontal force-force application point displacement (H0-Y0) relationship curve of the static load test, the horizontal force-force application point displacement gradient (H0-△Y0 / △H0) curve of the static load test and relevant specifications, a consistent conclusion is reached: under the conditions of the static load test used in this report, the horizontal critical load of a single pile is 76.50N, and the horizontal ultimate bearing capacity of a single pile is 153.00N.

[0095] 3.3. Pile horizontal displacement distribution curve

[0096] When the pile head is free, the burial depth is shallow, and the pile and the surrounding soil have not reached the stage of destruction, the rigid pile will rotate around a certain point on the pile axis like a rigid body after being subjected to horizontal force. Since rigid piles are used in static load tests, the position of the inflection point and the horizontal displacement of the pile body can be calculated by reverse calculation based on the displacement values ​​of the two dial indicators. The horizontal displacement distribution curves of the pile body for the two static load tests are shown in Figure 2. Figure 9 、 Figure 10 shown.

[0097] The horizontal displacement distribution curves of the pile body from the two static load tests show that as the horizontal load increases, the pile displacement at the soil surface and at the pile end both increase. When the horizontal load on the pile is less than the pile's ultimate horizontal load, the inflection point shifts slightly upward with increasing horizontal load, but the upward shift is not significant. When the horizontal load reaches the pile's ultimate horizontal load, the upward shift of the inflection point becomes more significant. This may be because as the horizontal load increases, the soil surrounding the pile gradually transitions from an elastic state to a plastic state. Under the same stress increment, soil deformation increases, leading to an increase in the inflection point. Before the horizontal load reaches the ultimate bearing capacity of the pile, the soil surrounding the pile mostly does not reach the plastic state, and the inflection point does not change significantly with load. However, after the horizontal load reaches the ultimate bearing capacity of the pile, the soil surrounding the pile mostly enters or is about to enter the plastic state. Under the same load increment, the pile displacement increases, and the change in the inflection point becomes more significant.

[0098] In the description of this utility model, unless otherwise specified, "plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific direction, be constructed, or operate in a specific direction, and therefore should not be construed as limiting this utility model. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0099] The above is only a specific implementation method of the present invention, but the scope of protection of the present invention is not limited to this. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A pile horizontal loading model test device, characterized in that: The device includes a rigid steel pipe pile, which is pre-buried in sand and soil with a burial depth of 55 cm; an adjustable iron ring is sleeved on the rigid steel pipe pile, and the iron ring is bolted with a steel strand, which passes through a pulley, and a tray is installed at the end of the steel strand. The pulley is installed on a pulley bracket, and the pulley bracket is fixed on the sand model box.

2. The pile horizontal loading model test device according to claim 1, characterized in that: The pulley bracket is installed at an appropriate position of the model box, and the center of the pulley is aligned with the center of the pile cross section to ensure that the steel strand acts on the center of the pile through the pulley during loading.

3. The pile horizontal loading model test device according to claim 1, characterized in that: A meter stand and two dial indicators are provided on the other side of the model box. The dial indicators are in horizontal contact with the pile body respectively. The extension lines of the dial indicators pass through the center of the pile body cross section and are used to measure the horizontal displacement of the pile during loading.

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