Method for determining proportionality coefficient of horizontal reaction coefficient of foundation soil

Abstract

The invention provides a method for determining a proportionality coefficient of a horizontal reaction coefficient of foundation soil, which comprises the following steps of: pouring a test pile to ensure that the perpendicularity deviation of the test pile is less than or equal to 1 percent; a counter-force beam is arranged on one side of the fender post to form a counter-force device; arranging a load applying device between the counter-force device and the test pile; and determining the proportionality coefficient of the horizontal reaction coefficient of the foundation soil by adopting a single multi-cycle loading method. By means of the technical scheme, accurate load data acting on the test pile can be obtained through direct testing, the problem that loading of the horizontal load test is difficult is solved, and the value of the proportionality coefficient m of the horizontal resistance coefficient of foundation soil can be obtained through data recording, curve drawing, analysis and calculation after loading.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and specifically to a method for determining the proportional coefficient of the horizontal reaction force coefficient of foundation soil. Background Technology

[0002] Currently, deep foundation pits are common in urban rail transit construction, leading to a high utilization rate of retaining piles. The "m" method is frequently used in retaining pile design. Among the various parameters designed using this method, the proportionality coefficient (m) of the foundation soil horizontal resistance coefficient is a major factor influencing the design results. The reasonableness of the calculated results is closely related to the value of m. At present, the main methods for determining the value of m, both domestically and internationally, are table lookup, formula methods, and horizontal load test methods. However, accurate data on the stress and deformation of retaining piles, as well as precise data on the horizontal reaction force of the foundation soil, cannot be obtained in deep foundation pits.

[0003] In summary, the existing technology has the following problems: it is impossible to obtain accurate data on the stress and deformation of piles and soil in the design of deep foundation pit retaining pile support. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of how to obtain accurate pile and soil stress and deformation data in the design of deep foundation pit retaining pile support.

[0005] Therefore, embodiments of the present invention provide a method for determining the proportionality coefficient of the horizontal reaction force coefficient of foundation soil, the method comprising:

[0006] Step 1: Pour the test pile to ensure that the verticality deviation of the test pile is less than or equal to 1%;

[0007] Step 2: Set the reaction beam on one side of the retaining pile to form a reaction device;

[0008] Step 3: Place the load application device between the reaction device and the test pile;

[0009] Step 4: Determine the proportional coefficient of the horizontal reaction force coefficient of the foundation soil using the single-item multi-cycle loading method.

[0010] Specifically, a force-transmitting cap is installed on the test pile, and the force-transmitting cap is connected to the load-applying device through a pressure plate.

[0011] Specifically, one end of the load-applying device is connected to the reaction beam, and the other end of the load-applying device is connected to the pressure plate.

[0012] Specifically, step one includes: pouring three test piles in one test in the same soil layer.

[0013] Specifically, a support is installed below the load-applying device, and the load-applying device is leveled by adjusting the height and position of the support.

[0014] Specifically, the load-applying device is a jack.

[0015] Specifically, step four includes:

[0016] Set each load increment to 1 / 10 to 1 / 15 of the maximum test load;

[0017] The load is gradually increased. After each load is applied, the horizontal displacement of the test pile is measured 4 minutes after the constant load is applied. Then, the load is unloaded to zero for 2 minutes before the residual horizontal displacement of the test pile is measured. This completes one loading and unloading cycle.

[0018] This process is repeated 5 times to complete the Level 1 load test;

[0019] Based on the measured horizontal displacement and residual horizontal displacement of the test pile, a curve was plotted, and the proportional coefficient of the horizontal reaction force coefficient of the foundation soil was analyzed and calculated.

[0020] The beneficial effects are as follows: The technical solution of this invention utilizes existing foundation pit retaining piles, which are easy to install and simple to calculate. This invention has a reasonable structure, employing pre-embedded test piles, reaction devices, fixing supports, leveling devices, and semi-melon-shaped pile caps, along with a load application device. Direct testing allows for accurate data on the load and deformation acting on the test piles, solving the problem of horizontal calculation for m-method piles. After loading, data is recorded, curves are plotted, and analysis and calculation yield the proportional coefficient m value of the foundation soil's horizontal resistance coefficient. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for determining the proportional coefficient of the horizontal reaction force coefficient of foundation soil according to an embodiment of the present invention;

[0022] Figure 2 This is a front view of the horizontal load testing device provided in an embodiment of the present invention;

[0023] Figure 3 This is a side view of the horizontal load testing device provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the force transmission cap structure provided in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the first type of test curve provided in the embodiments of the present invention;

[0026] Figure 6 This is a schematic diagram of the second type of test curve provided in the embodiments of the present invention.

[0027] Explanation of icon numbers:

[0028] 1. Foundation pit retaining piles; 2. Reaction beams; 3. Loading devices; 4. Test piles; 5. Force transmission caps. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention uses retaining piles for foundation pit reaction force, while the main beam, jacks, and semi-melon-shaped force transmission caps control the direction of force transmission. The proportional coefficient m of the horizontal resistance coefficient of the soil surrounding the test piles is measured through horizontal load tests.

[0031] In embodiments of the present invention, such as Figure 1 A method for determining the proportionality coefficient of the horizontal reaction force coefficient of foundation soil is provided, the method comprising:

[0032] Step 1: Pour test piles, ensuring the verticality deviation is less than or equal to 1%; pour three test piles in a single test on the same soil layer. Finally, calculate the horizontal displacement of the test piles and the average value of their residual horizontal displacement. This eliminates the influence of accidental factors such as single pile fabrication deviations and soil inhomogeneity, ensuring the uniformity of the initial state of the test objects (test piles) and providing a stable benchmark for subsequent data comparison and analysis.

[0033] Step Two: The reaction beam is installed on one side of the retaining piles to form a reaction device. The reaction beam is welded from steel plates, with ribs added to the top and bottom. The use of welded steel plates and ribs in the reaction beam enhances the overall structural strength and resistance to deformation, preventing deformation of the reaction device itself from interfering with load application accuracy. The reaction device relies on the retaining piles to establish a stable reaction support point, ensuring the continuous and stable transmission of horizontal loads.

[0034] Step 3: As Figure 2 The load-applying device is positioned between the reaction device and the test pile; wherein, the load-applying device is a jack. Figure 4 To better simulate the stress pattern of the test pile in the soil, a force-transmitting cap is installed on the test pile. That is, a force-transmitting cap is installed on the test pile, and the cap is connected to the load-applying device via a bearing plate. One end of the load-applying device is connected to the reaction beam, as shown below. Figure 3The other end of the load-applying device is connected to the bearing plate. A support is installed below the load-applying device, and the load-applying device is leveled by adjusting the height and position of the support. Specifically, by adjusting the height and position of the adjustable support test structure, the bubble in the level tube is centered to ensure that the load is horizontally transferred to the test pile during the test.

[0035] Step 4: Determine the proportional coefficient of the horizontal reaction force coefficient of the foundation soil using the single-phase multi-cycle loading method, specifically including:

[0036] Set each load increment to 1 / 10 to 1 / 15 of the maximum test load;

[0037] The load is gradually increased. After each load is applied, the horizontal displacement of the test pile is measured 4 minutes after the constant load is applied. Then, the load is unloaded to zero for 2 minutes before the residual horizontal displacement of the test pile is measured. This completes one loading and unloading cycle.

[0038] This process is repeated 5 times to complete the Level 1 load test;

[0039] Based on the measured horizontal displacement and residual horizontal displacement of the test piles, curves were plotted, and the proportionality coefficient of the horizontal reaction force coefficient of the foundation soil was analyzed and calculated. A typical test curve is shown below. Figure 5 , Figure 6 As shown.

[0040] Loading may be terminated if any of the following conditions are met:

[0041] ① The pile body breaks; ② The horizontal displacement exceeds 30-40mm (40mm for soft soil); ③ The horizontal displacement reaches the allowable value of horizontal displacement required by the design.

[0042] The entire test process, through controlling variables, optimizing force transmission, and standardizing loading methods, ultimately achieves accurate testing of the horizontal reaction characteristics of the foundation soil.

[0043] The technical solution of this invention utilizes existing foundation pit retaining piles, which are easy to install and simple to calculate. This invention has a reasonable structure, employing pre-embedded test piles, reaction devices, fixing supports, leveling devices, and semi-melon-shaped pile caps, along with a load application device. Accurate load data acting on the test piles can be obtained directly through testing, solving the problem of difficult horizontal load testing. After loading, data is recorded, curves are plotted, and analysis and calculation can yield the proportional coefficient m value of the horizontal resistance coefficient of the foundation soil.

[0044] Example:

[0045] This invention provides a proportionality coefficient method for determining the horizontal reaction coefficient of foundation soil. The method involves conducting a horizontal load test on pre-embedded short piles in a deep foundation pit, and the following steps are followed:

[0046] First, the equipment includes: foundation pit retaining piles, test piles, reaction devices, fixed supports, leveling devices, half-melon-shaped pile caps (for even distribution in the hands), and load application devices.

[0047] (1) Installation method of test device: the test pile is a new pile cast on site. Three test piles are cast in one test in the same soil layer. The verticality deviation of the test pile should not be greater than 1%.

[0048] (2) The reaction beam is placed in front of the retaining piles to form a reaction device. The reaction beam is made of welded steel plates, with ribs added to the top and bottom of the beam. The jacks are placed on the frame, and force transmission caps are installed on the test piles to better simulate the force distribution of the piles. The reaction beam and the retaining piles together form the reaction device.

[0049] (3) Leveling the force transmission system: By adjusting the height and position of the adjustable support test structure, the bubble in the level tube is centered to ensure that the load is horizontally transmitted to the test pile during the test.

[0050] (4) The load-applying device is a jack. One end of the jack is connected to the reaction beam, and the other end is connected to the pressure plate and the force transmission cap.

[0051] This test employs a single-cycle multi-cycle loading method. Load levels should be 1 / 10 to 1 / 15 of the design or estimated ultimate horizontal bearing capacity or the maximum test load. After each load level is applied, the horizontal displacement of the test pile can be measured after 4 minutes of dead load. Then, the load is unloaded to zero, paused for 2 minutes, and the residual horizontal displacement is measured, thus completing one loading / unloading cycle. This cycle is repeated 5 times to complete the test observation for the first load level. The test must not be interrupted. Loading can be terminated when any of the following conditions occur: ① pile fracture; ② horizontal displacement exceeds 30–40 mm (40 mm for soft soil); ③ horizontal displacement reaches the allowable horizontal displacement value required by the design.

[0052] Finally, by loading and recording the data, plotting the curves, and analyzing the data, the proportional coefficient m of the horizontal reaction force coefficient of the foundation soil can be obtained.

[0053] The technical solution of this invention utilizes existing foundation pit retaining piles, which are easy to install and simple to calculate. This invention has a reasonable structure, employing pre-embedded test piles, reaction devices, fixing supports, leveling devices, and semi-melon-shaped pile caps, along with a load application device. Accurate load data acting on the test piles can be obtained directly through testing, solving the problem of difficult horizontal load testing. After loading, data is recorded, curves are plotted, and analysis and calculation can yield the proportional coefficient m value of the horizontal resistance coefficient of the foundation soil.

[0054] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A proportional coefficient method for determining horizontal reaction coefficient of subsoil characterized in that, The method comprises: Step one: pouring test piles, so that the verticality deviation of the test piles is less than or equal to 1%; Step two: setting a counter-force beam on one side of the enclosing piles to form a counter-force device; Step three: setting an applied load device between the counter-force device and the test piles; Step four: determining the proportional coefficient of the horizontal counter-force coefficient of the foundation soil by using a single multi-cycle loading method.

2. The method of claim 1, wherein, A force transmission cap is installed on the test piles, and the force transmission cap is connected with the applied load device through a pressure bearing plate.

3. The method of claim 2, wherein, One end of the applied load device is connected with the counter-force beam, and the other end of the applied load device is connected with the pressure bearing plate.

4. The method of claim 1, wherein, Step one comprises: pouring three test piles in one test in the same soil layer.

5. The method of claim 1, wherein, A support is arranged below the applied load device, and the applied load device is leveled by adjusting the height and position of the support.

6. The method of claim 1, wherein, The applied load device is a jack.

7. The method of claim 1, wherein, Step four comprises: The load increment of each level is set to 1 / 10-1 / 15 of the maximum test load; The load is increased step by step, after each load is applied, the horizontal displacement of the test piles is measured after 4 minutes of constant load, then the load is unloaded to zero for 2 minutes, and the residual horizontal displacement of the test piles is measured, thus completing one loading and unloading cycle; This cycle is repeated 5 times to complete the test of one level of load; According to the measured horizontal displacement of the test piles and the residual horizontal displacement of the test piles, a curve is drawn, and the proportional coefficient of the horizontal counter-force coefficient of the foundation soil is analyzed and calculated.

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