Method for estimating tamping depth

Abstract

The present invention belongs to the technical field of foundation reinforcement, and specifically discloses a method for estimating the tamping depth, which includes obtaining the original density, original stress and tamping stress of the soil at each of multiple depths at a preset horizontal distance from the tamping point; determining the tamping density of the soil at each depth during the tamping process according to the original density, original stress and tamping stress; and estimating the tamping depth according to the tamping density and the maximum dry density of the soil at the corresponding depth. When determining the tamping depth, the present invention does not require sampling and excavation of the foundation after tamping, so it will not cause the soil to loosen after tamping and ensure the safety of subsequent construction. Further, the present invention can quickly estimate the tamping depth and tamping quality, and can avoid engineering risks caused by insufficient tamping treatment depth and unqualified tamping quality.

Description

Technical Field

[0001] The present invention discloses a method for estimating tamping depth, belonging to the technical field of foundation reinforcement. Background Art

[0002] The dynamic compaction method is a method of strongly compacting soil bodies such as foundations by allowing a heavy hammer to fall freely. The advantages of using it to treat foundations include: (1) Significantly improving the bearing capacity of the foundation: By continuously hitting the ground surface with a heavy hammer, the soil particles are rearranged and compacted, increasing the soil density and drainage performance, and improving the bearing capacity of the foundation. (2) Fast construction speed: Compared with the traditional filling method, the dynamic compaction method does not require a large amount of earthwork transportation and filling, reduces the construction period, and improves the engineering efficiency. (3) Wide applicability to soil types: The dynamic compaction method is applicable to most soil types, including sandy soil, unsaturated cohesive soil, collapsible loess and miscellaneous fill foundations. (4) Remarkable reinforcement effect: The foundation strength can be increased by 2 to 5 times, the compressibility can be reduced by 2 to 10 times, and the reinforcement influence depth can reach 6 to 10 meters. (5) Saving materials and cost: The dynamic compaction method does not require special building materials, saving the purchase, transportation, production and driving costs, and can save 50% to 70% of the investment compared with the pile foundation.

[0003] The dynamic compaction method is an effective method for treating collapsible foundations and soft foundations, which can eliminate problems such as collapsibility, liquefaction and uneven settlement of the foundation. However, there is no quantitative scientific basis for the selection of tamping energy, treatment depth, number of tamping times, etc. in the prior art, and only experience is relied on for discrimination, resulting in problems such as insufficient treatment depth and poor effect. In addition, when inspecting the effect after foundation treatment, sampling, excavation and testing are often used, resulting in problems such as relaxation of the reinforced soil body, inability to determine the deeper position, and distortion of test disturbance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for estimating tamping depth to solve the technical problems of relaxation of the reinforced soil body, inability to determine the deeper position, and distortion of test disturbance when inspecting the tamping effect using the prior art.

[0005] The present invention provides a method for estimating tamping depth, including:

[0006] Step 1: Obtain the original density, original stress and tamping stress during tamping of the soil body at each of multiple depths at a preset horizontal distance from the tamping point.

[0007] Step 2: Determine the tamping density of the soil body at each depth during tamping according to the original density, original stress and tamping stress.

[0008] Step 3: Estimate the tamping depth according to the tamping density and the maximum dry density of the soil body at the corresponding depth.

[0009] Preferably, step 2 specifically includes:

[0010] Determine the strain variable according to the difference between the tamping stress and the original stress.

[0011] Determine the tamping density of the soil at each depth during the tamping process according to the strain variable and the original density.

[0012] Preferably, determining the tamping density of the soil at each depth during the tamping process according to the strain variable and the original density specifically includes:

[0013] Obtain the moisture content of the soil at each depth.

[0014] Determine the density influence amount according to the moisture content and the strain variable.

[0015] Determine the tamping density of the soil at each depth during the tamping process according to the quotient of the original density and the density influence amount.

[0016] Preferably, determining the strain variable according to the difference between the tamping stress and the original stress specifically includes:

[0017] Determine the stress variable according to the difference between the tamping stress and the original stress.

[0018] Determine the strain variable according to the quotient of the stress variable and the compression modulus of the soil.

[0019] Preferably, step 3 specifically includes:

[0020] Determine the compaction coefficient of the soil at each depth according to the tamping density and the maximum dry density of the soil at the corresponding depth.

[0021] Estimate the tamping depth according to the compaction coefficient.

[0022] Preferably, determining the compaction coefficient of the soil at each depth according to the tamping density and the maximum dry density of the soil at the corresponding depth specifically includes:

[0023] Determine the maximum dry density of the soil according to the wet density and the relative density of the soil at each depth.

[0024] Determine the compaction coefficient of the soil at each depth according to the quotient of the tamping density and the maximum dry density of the soil at the corresponding depth.

[0025] Preferably, estimating the tamping depth according to the compaction coefficient specifically includes:

[0026] Select the compaction coefficient greater than the preset threshold as the first compaction coefficient.

[0027] Determine the depth value corresponding to the first compaction coefficient, and take the maximum depth value as the tamping depth.

[0028] Preferably, the original stress of the soil at each depth is determined according to the lateral pressure coefficient, unit weight and depth of the soil.

[0029] Preferably, the lateral pressure coefficient is determined according to the internal friction angle of the soil.

[0030] Preferably, the preset horizontal distance is 3m to 5m.

[0031] The tamping depth estimation method of the present invention has the following beneficial effects compared with the prior art:

[0032] The present invention does not need to sample and excavate the foundation after tamping, so it will not cause the soil to loosen after tamping, ensuring the safety of subsequent construction. Further, the present invention can quickly estimate the tamping depth and tamping quality, and can avoid the engineering risks caused by insufficient tamping treatment depth and unqualified tamping quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the installation position of the stress gauge in the embodiment of the present invention.

[0034] In the figure: 1 is an insertable stress gauge. DETAILED DESCRIPTION

[0035] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0036] The present invention provides a tamping depth estimation method, including:

[0037] Step 1, obtain the original density of the soil at each of multiple depths at a preset horizontal distance from the tamping point , original stress and the tamping stress during the tamping process . Among them, the original stress and the tamping stress are both horizontal stresses.

[0038] To obtain the original stress of the soil at each depth and the tamping stress during the tamping process, in the embodiment of the present invention, insertable stress gauges 1 are arranged at multiple depths at a preset horizontal distance from the tamping point, as Figure 1As shown in the figure. The preset horizontal distance is 3m to 5m. Within this distance range, the stress gauge 1 can be located within the depth range affected by tamping, so as to obtain relatively accurate stress, and at the same time, damage to the stress gauge 1 caused by tamping force can be avoided.

[0039] The original density in the embodiment of the present invention is the data obtained according to the exploration report.

[0040] Furthermore, the exploration report will also include the internal friction angle corresponding to the soil mass at different depths and unit weight . Therefore, the original stress of the soil mass at each depth can be obtained by using the stress gauge 1, or can be determined according to the lateral pressure coefficient of the soil mass , unit weight and the depth where it is located . Among them, the lateral pressure coefficient is determined according to the internal friction angle of the soil mass . Exemplarily, the original stress of the soil mass at each depth is determined according to formula (1) :

[0041] (1)

[0042] In the formula, is the lateral pressure coefficient, , is the internal friction angle; is the unit weight; is the depth.

[0043] Step 2. Determine the tamping density of the soil mass at each depth during the tamping process according to the original density and the tamping stress , specifically including: Step 2.1. Determine the strain variable

[0044] according to the difference between the tamping stress and the original stress , specifically including: Step 2.1.1. Determine the stress variable

[0045] according to the difference between the tamping stress and the original stress .

[0046] Step 2.1.2. Determine the strain variable by dividing the stress variable by the compression modulus of the soil mass.

[0047] Exemplarily, the strain variable is determined according to formula (2). :

[0048] (2)

[0049] Wherein, is the stress variable; is the compression modulus, which can be obtained from the exploration report; is the original stress; is the tamping stress.

[0050] Step 2.2. Determine the tamping density of the soil mass at each depth during the tamping process according to the strain variable and the original density , specifically including: :

[0051] Step 2.2.1. Obtain the water content of the soil mass at each depth, and this water content can be obtained from the exploration report.

[0052] Step 2.2.2. Determine the density influence amount according to the water content and the strain variable . Exemplarily, the density influence amount is determined according to formula (3):

[0053] (3)

[0054] Wherein, is the strain variable; is the water content.

[0055] Step 2.2.3. Determine the tamping density of the soil mass at each depth during the tamping process according to the quotient of the original density and the density influence amount , as shown in formula (4):

[0056] (4)

[0057] Wherein, is the original density; is the water content; is the stress variable; is the compression modulus.

[0058] Step 3. Estimate the tamping depth according to the tamping density and the maximum dry density of the soil mass at the corresponding depth, specifically including:

[0059] Step 3.1: Determine the compaction coefficient of the soil at each depth according to the tamping density and the maximum dry density of the soil at the corresponding depth Specifically, it includes:

[0060] Step 3.1.1: Determine the maximum dry density of the soil according to the wet density and the relative density of the soil at each depth, as shown in formula (5):

[0061] (5)

[0062] In the formula, is the wet density of the soil; is the relative density of the soil; is the optimum moisture content of the soil; , , The values of can all be obtained from the exploration report.

[0063] Step 3.1.2: Determine the compaction coefficient of the soil at each depth according to the quotient of the tamping density and the maximum dry density of the soil at the corresponding depth , specifically:

[0064] (6)

[0065] Step 3.2: Estimate the tamping depth according to the compaction coefficient Specifically, it includes:

[0066] Step 3.2.1: Select the compaction coefficient greater than the preset threshold as the first compaction coefficient.

[0067] The preset threshold in the embodiment of the present invention is 0.95.

[0068] Step 3.2.2: Determine the depth value corresponding to the first compaction coefficient, and take the maximum depth value as the tamping depth.

[0069] The tamping depth estimation method of the present invention does not require sampling and excavation of the foundation after tamping, so it will not cause the relaxation of the soil after tamping. Therefore, during the determination of the tamping depth, problems such as sampling disturbance and test disturbance will not be brought. The tamping depth estimation method of the present invention is applicable to various soil types, especially collapsible loess with certain structure.

[0070] The present invention can obtain the compaction coefficient of soil at different depths of the foundation by only testing the horizontal stress at different depths, and then determine whether the tamping reaches the effective treatment depth, so the depth estimation efficiency and construction efficiency can be greatly improved.

[0071] The present invention can obtain the compaction coefficient of soil at different depths during the tamping process in real time, so it can judge in real time whether the foundation treatment meets the standard and can visually determine whether the project quality meets the standard. The method of the present invention is simple to calculate, has clear mechanical concepts, high calculation accuracy, wide applicability, and can avoid engineering risks caused by insufficient tamping treatment depth.

[0072] The above are only several embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, making some changes or modifications using the technical content disclosed above is equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A method for estimating tamping depth, characterized in that, Including: Step 1: Obtain the original density, original stress, and tamping stress during the tamping process of the soil at each of multiple depths at a preset horizontal distance from the tamping point; Step 2: Determine the tamping density of the soil at each depth during the tamping process based on the original density, original stress, and tamping stress; Step 3: Estimate the tamping depth based on the tamping density and the maximum dry density of the soil at the corresponding depth, specifically including: Determine the compaction coefficient of the soil at each depth based on the tamping density and the maximum dry density of the soil at the corresponding depth, specifically including: Determine the maximum dry density of the soil based on the wet density and relative density of the soil at each depth; Determine the compaction coefficient of the soil at each depth based on the quotient of the tamping density and the maximum dry density of the soil at the corresponding depth, specifically: ， In the formula, is the compaction coefficient; is the tamping density; is the maximum dry density of the soil mass; is the original density; is the stress variable, and , is the tamping stress; is the original stress; is the compression modulus; is the water content; Estimate the tamping depth based on the compaction coefficient, specifically including: Select the compaction coefficient greater than the preset threshold as the first compaction coefficient; Determine the depth value corresponding to the first compaction coefficient, and take the maximum depth value as the tamping depth.

2. The method for estimating tamping depth according to claim 1, wherein Step 2 specifically includes: Determine the strain variable based on the difference between the tamping stress and the original stress; Determine the tamping density of the soil at each depth during the tamping process based on the strain variable and the original density.

3. The tamping depth estimation method according to claim 2, wherein Determine the tamping density of the soil at each depth during the tamping process based on the strain variable and the original density, specifically including: Obtain the water content of the soil at each depth; Determine the density influence amount based on the water content and the strain variable; Determine the tamping density of the soil at each depth during the tamping process based on the quotient of the original density and the density influence amount.

4. The tamping depth estimation method according to claim 2, wherein Determine the strain variable based on the difference between the tamping stress and the original stress, specifically including: Determine the stress variable based on the difference between the tamping stress and the original stress; Determine the strain variable based on the quotient of the stress variable and the compression modulus of the soil.

5. The method for estimating tamping depth according to claim 1, wherein The original stress of the soil at each depth is determined based on the lateral pressure coefficient, unit weight, and depth of the soil.

6. The method for estimating the tamping depth according to claim 5, characterized in that, The lateral pressure coefficient is determined based on the internal friction angle of the soil.

7. The method for estimating tamping depth according to claim 1, wherein The preset horizontal distance is 3m to 5m.

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