Box test device and test method for model carrier pile

Abstract

The present invention discloses a box test device for a model carrier pile, comprising a box frame system, a jack loading system arranged above the box frame system, and a sleeve system located in the box frame system. The present invention also discloses a box test method for a model carrier pile, wherein a soil layer is buried in the box frame system to a first preset depth; a sleeve system is placed in the box frame system, and the soil layer is continuously buried to the casing opening; gypsum mixed sand is used as a filling carrier filler to be filled into the casing; a jack loading system is used to pressurize a long rammer to tamp the carrier filler in the casing until it is compacted; a steel cage is placed in the casing, concrete is poured, and the casing is pulled out while pouring; after the pile in the casing is formed, the soil layer is peeled from top to bottom, and samples are taken layer by layer to determine the dry density, and the carrier pile forming condition is observed and analyzed. The present invention performs a full pile simulation test on the carrier pile to improve the referenceability of the carrier pile simulation experiment.

Description

Technical Field

[0001] The present invention relates to the technical field of model pile testing, and more specifically, to a box testing device and a testing method for a model carrier pile. Background Art

[0002] Carrier pile is a new type of pile developed in recent years. It is a new type of pile invented on the basis of rammed and expanded pile. Carrier pile has the characteristics of fast pile speed, high bearing capacity and low cost. It currently occupies a large market in some areas of my country.

[0003] The construction technology of carrier piles is similar to that of rammed-expanded piles. The basic construction process is: drill the hole to the designed depth (if the soil layer is soft, the pipe can be sunk to the designed depth) → lower the casing → add filler → compact with a rammer → measure the three-hit penetration (if unqualified, continue with the first two steps) → lower the steel cage → pour concrete → pull out the casing.

[0004] The advantages of carrier piles are simple construction technology, low cost, high bearing capacity, and environmental protection, but carrier piles also have certain disadvantages, such as: high noise during construction, serious soil squeezing effect, and difficult to control pile quality. Other piles need to place the pile end into the bearing layer, while carrier piles compact the soil layer that originally cannot be used as a bearing layer to achieve a certain strength to meet the bearing capacity requirements of the pile. The construction method and action mechanism of carrier piles are obviously different from other pile types. Carrier piles can be considered as a deep foundation treatment method.

[0005] At present, most indoor model tests of piles are conducted to explore the bearing capacity of piles, the failure mode of piles, etc., and there are relatively few indoor model tests on carrier piles. Some researchers have explored the shape of carriers, the influence range of carriers, etc. in indoor tests. Most of the influence range of carriers is studied through half-pile experiments. This experimental method is inconsistent with the actual working environment of piles, and there are certain deviations in the experimental results. Summary of the invention

[0006] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0007] Another object of the present invention is to provide a box test device and a box test method for a model carrier pile, which can completely simulate the pile-forming environment at the construction site and realize a full model study of the carrier pile.

[0008] In order to achieve these objects and other advantages according to the present invention, there is provided a box test device for a model carrier pile, comprising a box frame system, a jack loading system disposed above the box frame system, and a sleeve system located within the box frame system;

[0009] The box frame system includes a frame, an acrylic plate, and a hard glass plate, one side of the box frame system is set as a hard glass plate, and the other sides of the box frame system are set as acrylic plates;

[0010] The jack loading system includes a loading frame, a jack, and at least one pair of springs. The loading frame is arranged above the frame. The loading frame includes a fixed frame and a loading beam arranged up and down. The fixed frame is fixed on the frame, and the loading beam can move up and down relative to the fixed frame. The upper end of the jack is fixed on the fixed frame and the lower end is fixed on the loading beam. The upper end of the spring is fixed on the fixed frame and the lower end is fixed on the loading beam.

[0011] Preferably, it further comprises: a groundwater regulating system communicating with the inside and outside of the box frame system;

[0012] The groundwater regulation system comprises:

[0013] A plurality of perforated water pipes are arranged on the inner side wall of the box frame system, and the perforated water pipes extend out from the bottom of the box frame system;

[0014] The water collecting container is arranged outside the box frame system and is connected with a plurality of perforated water pipes through a pipe body.

[0015] Preferably, the fixing frame comprises a first crossbeam and a pair of fixing bars arranged at two ends of the first crossbeam in opposite directions, and the fixing bars are fixed on the frame.

[0016] Preferably, the loading beam comprises a beam body and two pairs of bending blocks arranged at two ends of the beam body opposite to each other, and each pair of bending blocks is distributed on both sides of the fixing bar.

[0017] Preferably, the end of the beam body is in a convex shape, and a pair of bending blocks are distributed on both sides of the protruding part of the beam body.

[0018] Preferably, the sleeve system comprises at least one sleeve, a bracket, at least one fastener and a plurality of fixing rods, the sleeve is fixed to the bracket via the fastener, and the bracket is fixed to the frame via the plurality of fixing rods.

[0019] The present invention provides a box test method for a model carrier pile, comprising the following steps:

[0020] Filling the soil layer in the box frame system to a first preset depth;

[0021] Place the sleeve system in the box frame system and continue to fill the soil layer to the casing opening;

[0022] Use gypsum mixed sand as a filling carrier to fill into the casing;

[0023] Using a jack loading system to pressurize a long rammer to tamp the carrier filler in the casing until it is compacted;

[0024] Place the steel cage into the casing, pour concrete, and pull out the casing while pouring;

[0025] After the pile in the casing is formed, the soil layer is peeled off from top to bottom, and samples are taken layer by layer to measure the dry density and draw images to observe the forming status of the carrier pile.

[0026] Preferably, during the landfill process, a ten-centimeter-thick soil layer is filled each time, and after being evenly compacted to eight centimeters, the landfill is continued until the first preset depth is reached;

[0027] The soil layer is a mixed soil type of sand and clay in a volume ratio of 1:1;

[0028] Annular sampling uses a ring knife, which has an inner diameter of 1 cm and a height of 0.5 cm.

[0029] Preferably, the specific method of sampling layer by layer to measure the dry density and draw the image is: determining the three-dimensional coordinate axis;

[0030] For single pile test:

[0031] Determine the sampling depth and the sampling spacing in the depth direction;

[0032] Determine the horizontal sampling points, which are radially arranged with the axis of the carrier pile as the center, and determine the interval angle between the radial axes and the sampling interval distance on the radial axes;

[0033] Soil samples are taken according to the determined sampling depth and the determined horizontal sampling points, weighed and processed, and the dry density is calculated;

[0034] Match the dry density with the sampling coordinate points, connect the values ​​of equal dry density on the horizontal plane and the plumb plane, and construct an equal dry density envelope diagram;

[0035] For multi-pile experiments:

[0036] Determine the sampling depth and the sampling spacing in the depth direction;

[0037] Determine the horizontal sampling points, which are radially arranged with the axis of the carrier pile as the center, and determine the interval angle between the radial axes and the sampling interval distance on the radial axes;

[0038] The horizontal sampling points are determined between the carriers of adjacent carrier piles in rows and columns with equal spacing;

[0039] Soil samples are taken according to the determined sampling depth and the determined horizontal sampling points, weighed and processed, and the dry density is calculated;

[0040] Match the dry density with the sampling coordinate points, connect the values ​​of equal dry density on the horizontal plane and the plumb plane, and construct an equal dry density envelope diagram.

[0041] Preferably, during the landfill process, the water level in the box frame system is adjusted by adjusting the height or position of the water level in the water collection container, thereby simulating the depth of groundwater in the foundation soil;

[0042] During the landfill process, the distance between the sleeves in the sleeve system is adjusted to simulate the spacing between different carrier piles.

[0043] The present invention has at least the following beneficial effects:

[0044] Compared with the half-pile experiment commonly used at present, this experiment studies some related issues of the carrier through the full-pile model experiment, making the carrier pile simulation experiment have a better reference effect;

[0045] The jack can directly pressurize the long rammer to compact the filler in the casing quickly and conveniently;

[0046] The side door can be opened and closed. The soil can be peeled off little by little by opening the side door to observe the shape of the carrier in the soil, and then study the shape of different fillers or carriers with different moisture contents;

[0047] The spacing between adjacent piles can be adjusted by changing the distance between the casings;

[0048] The regulation of groundwater level is not affected by the experimental process, and is convenient and comparable;

[0049] There is a water collection container connected to the foundation soil, which can be used to add water to the soil. Traditional indoor model experiments require the moisture content of the foundation soil to be matched in advance, and the moisture content is uncontrollable. This indoor experimental equipment can freely adjust the groundwater level, which speeds up the experiment and makes the experimental plan more diversified.

[0050] The expression of soil squeezing effect is more intuitive and the result is visible. The soil squeezing effect in carrier construction can be analyzed by drawing equal dry density envelope diagrams, and the optimal pile spacing of carrier piles can be obtained through analysis of the soil squeezing effect.

[0051] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a structural schematic diagram of a box test device for a model carrier pile of the present invention;

[0053] Figure 2 It is a structural schematic diagram of the loading device of the present invention;

[0054] Figure 3 It is a structural schematic diagram of the sleeve system of the present invention;

[0055] Figure 4 A schematic diagram of a three-dimensional coordinate system of a box frame system established for the present invention;

[0056] Figure 5 It is a schematic diagram of the distribution of sampling points on the horizontal plane in the single pile test of the present invention;

[0057] Figure 6 It is a schematic diagram of the distribution of plumb section sampling points in a single pile experiment of the present invention;

[0058] Figure 7 It is a schematic diagram of the distribution of another plumb section sampling point in a single pile test of the present invention;

[0059] Figure 8 It is a schematic diagram of the distribution of horizontal plane sampling points in the two-pile experiment of the present invention;

[0060] Fig. 9 It is a schematic diagram of the distribution of the plumb profile sampling points in the two-pile experiment of the present invention;

[0061] Fig.10 It is a schematic diagram of the distribution of horizontal plane sampling points in the three-pile experiment of the present invention;

[0062] Fig.11 It is a schematic diagram of an equal dry density envelope diagram on a horizontal plane drawn during a single pile test of the present invention;

[0063] Fig.12 It is a schematic diagram of an equal dry density envelope diagram on a plumb plane drawn during a single pile test of the present invention;

[0064] Fig.13 It is a schematic diagram of an equal dry density envelope diagram on a horizontal plane drawn during a two-pile experiment of the present invention;

[0065] Fig.14 It is a schematic diagram of an equal dry density envelope diagram on a vertical plane drawn during a two-pile experiment of the present invention.

[0066] Reference numerals: frame 1, acrylic plate 2, hard glass plate 3, loading frame 4, fixing frame 41, first crossbeam 411, fixing bar 412, loading crossbeam 42, beam body 421, bending block 422, jack 5, spring 6, perforated water pipe 7, water collection container 8, sleeve 9, bracket 10, fastener 11, fixing rod 12 DETAILED DESCRIPTION

[0067] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0068] It should be noted that, in the description of the present invention, the terms "upper end", "lower end", "inside", "outside", "bottom", "lower surface", "above", "up", "lower", "one side", "other sides", "both sides", "relatively arranged", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0069] like Figure 1 As shown, the present invention provides a box test device for a model carrier pile, comprising a box frame system, a jack loading system arranged above the box frame system, and a sleeve system located in the box frame system;

[0070] The box frame system includes a frame 1, an acrylic plate 2, and a hard glass plate 3. One side of the box frame system is set as the hard glass plate 3, and the other side of the box frame system is set as the acrylic plate 2;

[0071] It should be noted that Figure 1 This is the front view of the box test device for the model carrier pile. The box frame system of the test device is welded from steel pipes, and the side supports are high-strength waterproof acrylic plates, which have a certain ability to retain water and soil and will not deform or break due to soil compression. Two horizontal beams and three vertical beams are used behind the side baffles to strengthen the rigidity of the side baffles. This box test device can open the door on one side to facilitate soil unloading;

[0072] like Figure 2 As shown, the jack loading system includes a loading frame 4, a jack 5, and at least one pair of springs 6. The loading frame 4 is arranged above the frame 1. The loading frame 4 includes a fixing frame 41 and a loading beam 42 arranged up and down. The fixing frame 41 is fixed on the frame 1. The loading beam 42 can move up and down relative to the fixing frame 41. The upper end of the jack 5 is fixed on the fixing frame 41 and the lower end is fixed on the loading beam 42. The upper end of the spring 6 is fixed on the fixing frame 41 and the lower end is fixed on the loading beam 42.

[0073] The fixing frame 41 includes a first crossbeam 411 and a pair of fixing bars 412 arranged at two ends of the first crossbeam 411, and the fixing bars 412 are fixed on the frame 1;

[0074] The loading beam 42 includes a beam body 421 and two pairs of bending blocks 422 arranged at two ends of the beam body 421, each pair of bending blocks 422 is distributed on both sides of the fixing bar 412;

[0075] The end of the beam body 421 is in a convex shape, and a pair of bending blocks 422 are distributed on both sides of the protruding portion of the beam body 421. The two pairs of bending blocks 422 can move up and down along a pair of fixing bars 412 respectively, so that the loading beam 42 can move according to the movement of the jack 5.

[0076] It should be noted that a loading frame 4 is provided above the box frame system, and the carrier pile body can be pressurized by applying pressure to the beam body 421 through the jack 5.

[0077] In another technical solution, it also includes: a groundwater regulating system connected to the inside and outside of the box frame system;

[0078] The groundwater regulation system comprises: a plurality of perforated water pipes 7, which are arranged on the inner side wall of the box frame system, and the perforated water pipes 7 extend out of the bottom of the box frame system;

[0079] A water collecting container 8, which is arranged outside the box frame system and is connected with a plurality of perforated water pipes 7 through a pipe body;

[0080] The water collecting container 8 can be fixed on the frame 1 or in other ways. If the water collecting container 8 needs to be high, it can also be placed on a structure with a certain height. The groundwater regulating system can control the groundwater level in the box test device by adjusting the water level in the water collecting container 8 or raising the height of the water collecting container 8.

[0081] In another technical solution, Figure 3 As shown, the sleeve system includes at least one sleeve 9, a bracket 10, at least one fastener 11 and a plurality of fixing rods 12, and the sleeve 9 is fixed to the bracket 10 by the fastener 11. The sleeve 9 is provided with a fastener 11, and the fastener 11 is a bolt lock. The spacing between the same row of piles can be adjusted by fixing the sleeve 9 at different positions of the transverse rod of the bracket 10. The spacing between the two rows of piles can be controlled by controlling the spacing between the two transverse rods. The number of fixed sleeves 9 can also be changed. When doing an experiment with three piles, two sleeves 9 are fixed on one of the transverse rods, and one sleeve 9 is fixed at the middle position of another transverse rod. In addition, the bracket 10 can also fix the sleeve 9 so that it will not tilt during the construction of adjacent piles. The bracket 10 is fixed to the skeleton 1 by a plurality of fixing rods 12, which further completes the fixing of the bracket to prevent tilting.

[0082] In the present invention, the equipment installation process of the box device of the model carrier pile is as follows: fix the perforated water pipe 7 to the inner side of the skeleton 1 in the box frame system, and then assemble three side panels and a glass side door; connect the water collection container 8 to the perforated water pipe 7; and compose a jack loading system with a jack 5, a loading frame 4, and a spring 6, and fix it on the box frame system.

[0083] The present invention provides a box test method for a model carrier pile, comprising the following steps:

[0084] S1. Fill the soil layer in the box frame system to a first preset depth. During the landfilling process, fill a ten-centimeter-thick soil layer each time, compact it evenly to eight centimeters, and then continue to fill until it reaches the first preset depth; the soil layer is a mixed soil type of sand and clay with a volume ratio of 1:1.

[0085] S2. Place the sleeve system in the box frame system and continue to fill the soil layer to the opening of the sleeve 9. It should be noted that the soil layer should not be filled into the sleeve 9.

[0086] S3. Use gypsum mixed sand as a filling carrier filler to fill the casing 9; the filler added in the actual project is often dry hard concrete. Indoor tests do not need to use such a high-strength gel material. Indoor model tests can use gypsum mixed sand as a filling carrier filler. Gypsum can be made of colored gypsum, which is convenient for studying the shape of the carrier in the future. Gypsum is a fast-hardening gel material. Indoor tests generally require gel materials to have a fast setting speed and a certain strength. Gypsum is the most suitable substitute for cement in indoor tests. The purpose of choosing colored gypsum is to have sufficient contrast with the soil layer, which is convenient for observing the shape of the carrier under different filler amounts.

[0087] S4, using the jack loading system to pressurize the long rammer to tamp the filler in the casing 9 until it is compacted. The jack loading system applies force to the long rammer through the movable jack 5 and then transmits it to the lower filler to achieve the compaction effect;

[0088] S5. Put the steel cage into the casing 9, pour concrete, and pull out the casing 9 while pouring; the pile body adopts the concrete pile body design, which restores the actual state of the carrier pile as much as possible, so as to facilitate the study of the bonding effect between the carrier and the body. The steel cage is tied with iron wire. In the actual experiment, the pile load is very small, so the steel cage tied with iron wire is sufficient for the experimental needs.

[0089] S6. After the pile is formed, the soil layer is peeled from top to bottom, and samples are taken layer by layer to observe the formation of the carrier pile. The sampling is around the pile body and the carrier, and a number of samples are taken from each layer to ensure that the sample capacity is sufficient. After sampling, a drying experiment is carried out, and the weight is weighed after drying to determine the dry density of the soil sample; a ring knife is used for annular sampling, and the inner diameter of the ring knife is 1 cm and the height is 0.5 cm.

[0090] In the actual construction process of carrier piles, the construction of the carrier may cause the pile ends of the adjacent piles to move upward. This is because the soil squeezing effect generated during the construction of the carrier pile causes the pile body to move upward. Therefore, the study of the soil squeezing effect of the carrier pile is also very important. At present, there are relatively few studies on the soil squeezing effect of carrier piles. This test equipment can meet the research of the soil squeezing effect. The study of the soil squeezing effect is based on the density of the soil around the pile and the carrier. The purpose of the ring cutter soil sampling is to obtain the dry density of the soil, and to judge the density of the soil by the dry density. Mathematical software is used to visualize the obtained position coordinates and the corresponding dry density data to obtain an equal dry density envelope diagram. The equal dry density envelope diagram can be used to analyze the influence range of the carrier and the soil squeezing effect between the carriers. The optimal pile spacing of the carrier pile can be obtained through the envelope diagram.

[0091] This embodiment provides a specific method for obtaining an isodense density envelope diagram, as follows:

[0092] 1. Preparation before the experiment

[0093] (1) Label each ring cutter and weigh it to obtain the mass Di (i=1, 2, 3, ... n) of each ring cutter; label each soil sample box and weigh it to obtain the mass Hi (i=1, 2, 3, ... n) of each soil sample box.

[0094] (2) Group the cutter rings and soil sample boxes and calculate the total mass mi of the cutter rings and soil sample boxes in each group, mi = Di + Hj.

[0095] (3) Prepare the materials needed for the experiment: soil, sand, colored plaster, water, etc.

[0096] 2. Experimental process

[0097] (1) Determination of sampling coordinate system: First determine the three-dimensional coordinate axis, with the three adjacent sides of the model test box as the X, Y, and Z axes, and the intersection of the three sides as point O, such as Figure 4 As shown;

[0098] (2) Determination of sampling range: The carrier pile has a certain soil squeezing effect during construction. In order to study its influence range well, it is particularly important to determine the sampling range. According to the current "Technical Standards for Carrier Piles" (JTJ / T 135-2018), the influence range of the soil squeezing effect of the carrier pile is approximately 4 times the pile diameter. Therefore, the test sampling starts from 2 times the pile diameter at the upper edge of the carrier to 3 times the pile diameter below the bottom of the carrier. The sampling range around the pile body is 5 times the pile diameter (extending 2.5 times the pile diameter from the side of the pile body, and symmetrically according to the pile diameter, the sampling range is 5 times the pile diameter). For example, if the pile body is 40 cm long and 10 cm in diameter, the first layer of sampling is 20 cm from the bottom of the pile body. The plane sampling range is a circular range of 25 cm outward from the pile axis.

[0099] (3) Sampling plane processing: To ensure the accuracy of the sampling coordinates, the X and Y coordinates of each layer of sampling coordinates need to be accurate on both sides, and the accuracy of the Z coordinate must be guaranteed. The X and Y coordinates are based on the side wall of the box, and the coordinate measurement accuracy is relatively high. However, the unevenness of the peeled soil layer will cause the Z coordinate of the actual sampling point to be inconsistent with the designed sampling point. Therefore, the box frame system is designed to set the acrylic plate on the opposite side of the long side to an acrylic plate with a height of 3-5cm. When peeling the soil layer, the acrylic plate is pulled out by the way, and the soil layer is peeled off with the acrylic plates on both sides as the reference to ensure that there are no protruding parts on each sampling plane, and to ensure that the sampling soil layer is not over-peeled, causing the sampling soil layer to be concave.

[0100] (4) Sampling and representation of sampling positions

[0101] Single pile sampling: The horizontal sampling of a single pile is xy plane sampling. The horizontal sampling is radially spread out around the axis of the carrier pile. Figure 5 . For horizontal sampling, first take a sampling reference line parallel to the X-axis, mark it as the 0-axis, and sample at certain intervals on the 0-axis. Then rotate the 0-axis counterclockwise at a certain angle (the angle is selected according to your needs) with the axis of the carrier pile as the center. After the rotation, locate the 1-axis, and then mark the sampling positions at equal intervals on the 1-axis. The sampling interval along the extension direction of the 1-axis is the same as that of the 0-axis. After sampling, locate other axes (2, 3, ...n) in the same way and perform sampling operations.

[0102] The sampling in the depth direction of a single pile is done in the z-axis direction. The sampling in the depth direction makes the upper and lower sampling positions overlap as much as possible. When approaching the carrier, it is necessary to avoid the carrier and not to destroy the carrier shape, let alone sampling on the carrier. The depth direction is usually 5 cm apart as a layer (as consistent as possible with the height of the acrylic sheet on the side, and the control of the plane is convenient through the restriction of the acrylic sheet). First, determine the depth of the first layer, peel the soil from the top to the specified depth, and then level the sampling plane. Sampling is done according to the above-mentioned horizontal plane sampling method. After sampling, the coordinates of the sampling points are clearly recorded (x, y, z), and then the soil is peeled to the next layer of depth. Continue horizontal plane sampling, record coordinates, etc. The sampling plumb plane section is shown in the figure. Figure 6 and Figure 7 The sampling of other depths is the same as this until the sampling reaches the experimental range.

[0103] Sampling coordinate representation method: Figure 5 As shown in the figure, the single pile sampling method is radial. In order to quickly, intuitively and accurately indicate the location of a sampling point, it is necessary to display the number of axes in the radial axis in the plane and the number of layers of sampling on the plumb plane. The sampling point coordinate representation method (x i,j ,y i,j , z k )(i refers to the specific axis in the plane, j refers to the sampling point position along the radial axis, and k refers to the specific layer number of the sampling in the vertical direction; i = 0, 1, 2...n; j = 1, 2, 3...n; k = 1, 2, 3...n), for example, the coordinate representation method of the fourth sampling point on the 0 axis of the first layer is (x 0,4 ,y 0,4 , z1).

[0104] Two-pile sampling: The horizontal sampling of two-pile sampling is different from that of single-pile sampling. The area between the two pile carriers is sampled in rows and columns with equal spacing. The area not affected by the adjacent piles is still sampled radially. For specific sampling methods, see Figure 8 The coordinates of the radial sampling part are still expressed in the same way as the single pile. The sampling position expression method of the row and column distribution is similar. The difference is that the axis numbers of the row and column distribution area are letters, and they are recorded as A axis, B axis, C axis, ..., N axis. The coordinate expression method is (x N,j ,y N,j , z k ), N is A axis, B axis, C axis, ..., N axis, and N is any letter from A to Z.

[0105] The plumb plane sampling method for two piles is the same as that for a single pile. The sampling interval and coordinate representation in the vertical direction are the same as those for a single pile. Fig. 9 As shown, it should be noted that care should be taken to avoid the carrier position, not to damage the carrier, and to ensure the integrity of the carrier.

[0106] Three-pile sampling: The horizontal sampling of three-pile sampling is different from that of two-pile sampling. The areas between the three-pile carriers that are not affected by the adjacent piles are still sampled in a radial manner, and the areas between the three-pile carriers that are affected by the adjacent piles are sampled in the form of equal-spaced rows. For specific sampling methods, see Fig.10 The area of ​​the row and column sampling method is recorded from top to bottom as the a-axis, b-axis, c-axis, ..., n-axis, and the axis formed by the radial sampling method is recorded digitally, and the coordinate footnotes are set as needed.

[0107] It should be noted that you should avoid the carrier position, do not damage the carrier, and ensure the integrity of the carrier.

[0108] (5) Sampling precautions and subsequent processing

[0109] Press the ring knife into the soil, slowly take out the ring knife to avoid affecting the surrounding soil, then scrape off the soil on both sides of the ring knife, put the ring knife and the soil sample into the soil sample box, pay attention to the soil sample coordinates and the record of the soil sample box and ring knife number to prevent mistakes; put the soil sample box containing the soil sample into an oven and dry it for 12 hours, then weigh it to get the mass Mi (i=1, 2, ....n) of each soil sample together with the ring knife and soil sample box.

[0110] 3. Data processing

[0111] (1) Physical quantity solution and data statistics

[0112] Soil sample drying mass m si =M i -m i ,

[0113] m si The weight of the soil sample after drying;

[0114] M i Total weight of soil sample + ring cutter + soil sample box;

[0115] m i Weight of ring cutter + soil sample box.

[0116] Soil sample dry density:

[0117] ρ s Dry density of soil sample;

[0118] m s The mass of the sample after drying;

[0119] V sample volume;

[0120] Where: The volume of the soil sample is the volume inside the ring cutter V = ΠR 2 h

[0121] R ring cutter inner radius;

[0122] h ring knife height;

[0123] Soil density calculation formula:

[0124] Soil compactness is usually defined by relative density;

[0125] ρ0 soil sample dry density;

[0126] ρ is the dry density of soil without voids;

[0127] Through the analysis of the density calculation formula, we can understand that the greater the dry density of the soil sample, the greater the density of the soil, so the dry density can be used to indirectly indicate the density of the soil.

[0128] (2) Drawing of dry density contour lines

[0129] The dry density values ​​and coordinate point data in the above test process are processed and matched.

[0130] ① Treatment methods for the impact range of a single pile

[0131] When the number of test piles is one, in order to reflect the influence range well, select the coordinates with the same k value and the dry density corresponding to the plane where the k value is located, and use the software to draw a two-dimensional dry density contour map. When drawing the dry density contour line, when the dry density of points with different i-axis and the same j value on the k-value plane is not equal, the dry density values ​​at points j-1 and j+1 on the i-axis of the k-value plane can be used, and the dry density values ​​equal to the remaining axes can be selected between points j-1 and j+1 on the i-axis for drawing. Connect the dry density contour lines with the same k value during the test to form an equal dry density envelope diagram, such as Fig.11 As shown, the envelope diagram is centered on the carrier pile or carrier and is a closed contour diagram similar to a mountain peak (single peak).

[0132] At the same time, in order to better reflect its influence range, the vertical plane where one of the axes is located is selected for research, all the data of the vertical plane are represented in the mathematical drawing software, and the points with equal values ​​in the vertical plane are connected to form the equal dry density envelope diagram of the vertical plane, such as Fig.12 shown.

[0133] ② Methods for dealing with the mutual influence range of multiple pile carrier piles

[0134] The research on the influence range of multi-pile carriers and soil squeezing effect is relatively complex. Although the soil squeezing effect also has certain regularity, its symmetry is relatively weak. When drawing, the multiple piles are symmetrically separated, and the coordinates and dry density values ​​corresponding to the single piles are extracted. The equal dry density envelope diagrams of the horizontal plane and the plumb plane are first drawn in the form of a single pile, and then combined. The combined viewing is to be able to intuitively see the equal dry density values ​​of the multiple piles, such as Fig.13 and 14 In the process of multi-pile research, the main purpose is to obtain the distance between two adjacent piles without affecting them. In the implementation process, the positions of the two piles can be set according to the distance between the two adjacent piles obtained in the study.

[0135] When drawing the three-pile experiment, the drawing is based on the actual dry density measured.

[0136] In order to understand the effects of different carrier fillers, different water levels (when the soil layer contains groundwater, the side door needs to be blocked, and the gap of the side door needs to be wiped clean and taped with tin foil tape to prevent water from flowing out of the gap), and different pile spacing on the simulation results, experimental research is still needed.

[0137] (1) Study on the influence of filler amount and filler type on carrier shape

[0138] The pile-forming effect of the carrier depends to a certain extent on the amount of filler, which affects the three-hit penetration, and the three-hit penetration is the criterion for judging the bearing quality of the carrier pile. The more filler, the smaller the three-hit penetration, and the less filler, the less bearing capacity of the carrier pile may be. Secondly, the shape of the carrier varies with the amount of filler. At present, the half-pile model test is usually used to study the shape of the carrier pile. The shape of half of the carrier is observed through a glass plate. Such a half-pile test will affect the development of the carrier due to the boundary effect of the glass plate, and this half-pile test cannot completely restore the true state of the carrier. The design of this test equipment is to open the door from one side to peel off the soil around the pile and observe the carrier shape.

[0139] Gypsum is used as a cementing material for carrier molding. During the test, the carrier will become solid due to the hardening of the gypsum. After the pile body hardens, slowly open the side door and use a shovel or other small equipment to slowly peel off the soil vertically until the carrier is seen (the carrier uses colored gypsum as a cementing material, and the boundary line with the soil is very obvious). Then slowly peel off the soil around the carrier. Every time a certain depth of soil is peeled off, the diameter of the carrier is measured and photographed for record, which is more convenient for observing the shape of the carrier and unloading the soil.

[0140] (2) Regulation of groundwater level

[0141] The carrier construction principle of the carrier pile is similar to the deep foundation treatment, and the water content of the foundation soil will affect the quality of the carrier construction. This test box test device can meet the control of the water level of the foundation soil. A perforated water pipe 7 is arranged on the inner wall of the box test device, and the perforated water pipe 7 is connected to the external water collecting container 8 through the pipe body. In the actual test process, the depth of groundwater in the foundation soil can be realized by controlling the height of the water collecting container 8 to control the head pressure. In this way, different moisture contents in the construction process of the carrier pile can be simulated, which is conducive to comparative tests. The traditional model test box can only carry out moisture proportioning before the foundation soil is placed in the model box. This method has a complicated experimental process, relatively complicated moisture content control, and the comparative test effect is not obvious. This box test device can greatly simplify this test process and greatly shorten the test time. This box test device can open the door on the side. After the test is over, the side door can be opened to study the construction quality of the carrier under different moisture contents. A loading device can be added to the box frame system to conduct a pile model load test to further study the bearing capacity of the pile under different moisture contents, whether the influence range of the carrier under different moisture contents is consistent, whether the combination of the carrier and the pile body is affected by the moisture content of the soil layer, and whether the soil squeezing effect between piles will be affected by groundwater. The above experimental operations are all studied through the dry density envelope diagram.

[0142] (3) Adjust the distance between different piles

[0143] As a form of soil-squeezing pile, the interaction between adjacent piles cannot be ignored. The looseness of the soil layer in the indoor test is much greater than that in the actual project. Therefore, when the carrier pile is tested in the indoor model, it is easy to squeeze the casing of the adjacent pile. Therefore, the casing of the carrier pile is designed when designing the indoor model test box, such as Figure 3 , a fastener 11 that can lock the casing 9 is designed on the casing. The fastener 11 is constrained by the bracket 10 so that it will not be offset due to the soil squeezing effect or vibration during the carrier construction process. In this way, the pile spacing can be accurately controlled and interference from other unnecessary factors can be eliminated. The spacing of the piles is controlled by controlling the spacing of the casing on the transverse rod. After the piles are formed, a load test is carried out through a loading device to explore the bearing capacity of the carrier piles under different pile spacings. The carrier can also be peeled off from the soil after the carrier hardens, and the carrier shape under different pile spacings is studied to explore the influence of the carrier pile spacing on the construction of the adjacent pile carrier.

[0144] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A box test method for a model carrier pile, characterized in that: The following steps are involved: Filling the soil layer in the box frame system to a first preset depth; Place the sleeve system in the box frame system and continue to fill the soil layer to the casing opening; Use gypsum mixed sand as a filling carrier to fill into the casing; Using a jack loading system to pressurize a long rammer to tamp the carrier filler in the casing until it is compacted; Place the steel cage into the casing, pour concrete, and pull out the casing while pouring; After the piles in the casing are formed, the soil layers are peeled off from top to bottom, and samples are taken layer by layer to measure the dry density and draw images, and the forming conditions of the carrier piles are observed and analyzed; The specific method of sampling layer by layer to measure the dry density and draw the image is as follows: determine the three-dimensional coordinate axis; For single pile test: Determine the sampling depth and the sampling spacing in the depth direction; Determine the horizontal sampling points, which are radially arranged with the axis of the carrier pile as the center, and determine the interval angle between the radial axes and the sampling interval distance on the radial axes; Soil samples are taken according to the determined sampling depth and the determined horizontal sampling points, weighed and processed, and the dry density is calculated; Match the dry density with the sampling coordinate points, connect the values ​​of equal dry density on the horizontal plane and the plumb plane, and construct an equal dry density envelope diagram; For multi-pile experiments: Determine the sampling depth and the sampling spacing in the depth direction; Determine the horizontal sampling points, which are radially arranged with the axis of the carrier pile as the center, and determine the interval angle between the radial axes and the sampling interval distance on the radial axes; The horizontal sampling points are determined between the carriers of adjacent carrier piles in rows and columns with equal spacing; Soil samples are taken according to the determined sampling depth and the determined horizontal sampling points, weighed and processed, and the dry density is calculated; Match the dry density with the sampling coordinate points, connect the values ​​of equal dry density on the horizontal plane and the plumb plane, and construct an equal dry density envelope diagram.

2. The box test method of the model carrier pile according to claim 1, characterized in that: During the landfill process, a ten-centimeter-thick soil layer is filled each time, and after being evenly compacted to eight centimeters, the landfill is continued until the first preset depth is reached; The soil layer is a mixed soil type of sand and clay in a volume ratio of 1:1; Annular sampling uses a ring knife with an inner diameter of 1 cm and a height of 0.5 cm.

3. The box test method of the model carrier pile according to claim 1, characterized in that: During the landfill process, the water level in the box frame system is adjusted by adjusting the height or position of the water level in the water collection container, thereby simulating the depth of groundwater in the foundation soil; During the landfill process, the distance between the sleeves in the sleeve system is adjusted to simulate the spacing between different carrier piles.

4. A box test device for a model carrier pile, applied to the box test method for a model carrier pile as claimed in any one of claims 1 to 3, characterized in that: It includes a box frame system, a jack loading system arranged above the box frame system, and a sleeve system located in the box frame system; The box frame system includes a frame, an acrylic plate, and a hard glass plate. One side of the box frame system is provided with an openable hard glass plate, and the other sides of the box frame system are provided with acrylic plates. The jack loading system includes a loading frame, a jack, and at least one pair of springs. The loading frame is arranged above the frame. The loading frame includes a fixed frame and a loading beam arranged up and down. The fixed frame is fixed on the frame, and the loading beam can move up and down relative to the fixed frame. The upper end of the jack is fixed on the fixed frame and the lower end is fixed on the loading beam. The upper end of the spring is fixed on the fixed frame and the lower end is fixed on the loading beam.

5. The box test device for the model carrier pile according to claim 4, characterized in that: Also includes: A groundwater regulating system connected to the inside and outside of the box frame system; The groundwater regulation system comprises: A plurality of perforated water pipes are arranged on the inner side wall of the box frame system, and the perforated water pipes extend out from the bottom of the box frame system; The water collecting container is arranged outside the box frame system and is connected with a plurality of perforated water pipes through a pipe body.

6. The box test device for the model carrier pile according to claim 4, characterized in that: The fixing frame includes a first crossbeam and a pair of fixing bars arranged opposite to each other at two ends of the first crossbeam, and the fixing bars are fixed on the frame.

7. The box test device for the model carrier pile according to claim 6, characterized in that: The loading crossbeam comprises a beam body and two pairs of bending blocks arranged oppositely at two ends of the beam body, and each pair of bending blocks is distributed on both sides of the fixing bar.

8. The box test device for the model carrier pile according to claim 7, characterized in that: The end of the beam body is in a convex shape, and a pair of bending blocks are distributed on both sides of the protruding part of the beam body.

9. The box test device for the model carrier pile according to claim 4, characterized in that: The sleeve system comprises at least one sleeve, a bracket, at least one fastener and a plurality of fixing rods. The sleeve is fixed to the bracket via the fastener, and the bracket is fixed to the frame via the plurality of fixing rods.

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