Tamping depth estimation method

Abstract

The invention belongs to the technical field of foundation reinforcement, and particularly discloses a tamping depth estimation method which comprises the following steps: acquiring the original density and original stress of a soil body at each depth in a plurality of depths at a preset horizontal distance from a tamping point and the tamping stress in the tamping process; the tamping density of the soil body at each depth in the tamping process is determined according to the original density, the original stress and the tamping stress; and the tamping depth is estimated according to the tamping density and the maximum dry density of the soil body at the corresponding depth. When the tamping depth is determined, the tamped foundation does not need to be sampled and excavated, so that soil loosening after tamping is avoided, and subsequent construction safety is guaranteed. Furthermore, the tamping depth and the tamping quality can be quickly estimated, and the engineering risk caused by insufficient tamping treatment depth and substandard tamping quality can be avoided.

Description

Technical Field

[0001] The invention discloses a tamping depth estimation method and belongs to the technical field of foundation reinforcement. Background Art

[0002] Dynamic compaction is a method of compacting the foundation and other soil bodies by free falling of a heavy hammer. The advantages of using it to treat the foundation include: (1) Significant improvement in foundation bearing capacity: By continuously hitting the surface with a heavy hammer, the soil particles are rearranged and compacted, increasing soil density and drainage performance, and improving foundation bearing capacity. (2) Fast construction speed: Compared with traditional filling methods, dynamic compaction does not require a large amount of earthwork transportation and filling, reducing the construction period and improving engineering efficiency. (3) Wide range of applicable soil types: Dynamic compaction is applicable to most soil types, including sandy soil, unsaturated clay soil, collapsible loess and miscellaneous fill foundations. (4) Significant 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 depth can reach 6 to 10 meters. (5) Saving materials and construction costs: Dynamic compaction does not require special building materials, saving the cost of purchase, transportation, production and driving. Compared with pile foundations, it can save 50% to 70% of investment.

[0003] Dynamic tamping is an effective method for dealing with collapsible foundations and weak foundations, and can eliminate problems such as collapsibility, liquefaction, and uneven settlement of the foundation. However, the existing technology has no quantitative scientific basis for the selection of tamping energy, treatment depth, and number of tamping times, and only relies on experience to make judgments, resulting in problems such as insufficient treatment depth and poor results. In addition, when testing the effect of foundation treatment, sampling, excavation, and testing are often used, resulting in loosening of the reinforced soil, inability to determine deeper positions, and test disturbance distortion. Summary of the invention

[0004] The purpose of the present invention is to provide a method for estimating the tamping depth to solve the technical problems of loosening of reinforced soil, inability to determine deeper positions, and distortion of test disturbances when using the existing technology to test the tamping effect.

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

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

[0007] Step 2: Determine the tamping density of the soil at each depth during the tamping process 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 at the corresponding depth.

[0009] Preferably, step 2 specifically includes:

[0010] A strain variable is determined based on the difference between the impact stress and the original stress.

[0011] The compaction density of the soil at each depth during the compaction process is determined 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] Get the soil moisture content at each depth.

[0014] The density influence variable is determined according to the moisture content and the strain variable.

[0015] The compaction density of the soil at each depth during the compaction process is determined according to the quotient of the original density and the density influence quantity.

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

[0017] A stress variable is determined based on the difference between the impact stress and the original stress.

[0018] The strain variable is determined based on the quotient of the stress variable and the compression modulus of the soil.

[0019] Preferably, step 3 specifically includes:

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

[0021] The tamping depth is estimated based on the compaction factor.

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

[0023] The maximum dry density of the soil is determined based on the wet density and relative density of the soil at each depth.

[0024] The compaction coefficient of the soil at each depth is determined based on 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] A compression coefficient greater than a preset threshold is selected as the first compression 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, bulk density 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~5m.

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

[0032] The present invention does not require sampling and excavation of the foundation after tamping, so the soil will not loosen after tamping, ensuring the safety of subsequent construction. Furthermore, the present invention can quickly estimate the tamping depth and tamping quality, avoiding engineering risks caused by insufficient tamping depth and substandard tamping quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the installation position of the stress gauge in the embodiment of the present invention.

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

[0035] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may 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 prevent unnecessary details from obstructing the description of the present invention.

[0036] The present invention provides a method for estimating tamping depth, comprising:

[0037] Step 1: Obtain the original density of the soil at each depth at multiple depths at a preset horizontal distance from the tamping point , original stress and the ramming stress during the ramming process The original stress is and impact stress All stresses are in the horizontal direction.

[0038] To obtain the original stress of the soil at each depth And the ramming stress during the ramming process In the embodiment of the present invention, an inserted stress gauge 1 is provided at multiple depths of a preset horizontal distance from the tamping point, such as Figure 1The preset horizontal distance is 3m~5m. Within this distance range, the stress gauge 1 can be located within the impact depth range, thereby obtaining more accurate stress and preventing the stress gauge 1 from being damaged by the impact force.

[0039] The original density in the embodiment of the present invention The data are obtained based on the survey report.

[0040] Furthermore, the survey report will also include the internal friction angles of soil at different depths. and bulk density Therefore, the original stress of the soil at each depth can be obtained using stress gauge 1, or it can be obtained based on the lateral pressure coefficient of the soil , bulk density and depth Determine. Among them, the side pressure coefficient According to the internal friction angle of the soil For example, the original stress of the soil 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 bulk density; For depth.

[0043] Step 2: According to the original density , original stress and impact stress Determine the compaction density of the soil at each depth during the compaction process , specifically including:

[0044] Step 2.1: According to the impact stress and original stress The difference between the strain variables , specifically including:

[0045] Step 2.1.1: According to the impact stress and original stress The difference between the two determines the stress variable .

[0046] Step 2.1.2: According to stress variables The compression modulus of the soil The quotient determines the strain variable .

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

[0048] (2)

[0049] In the formula, is the stress variable; is the compression modulus, which can be obtained from the survey report; is the original stress; is the impact stress.

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

[0051] Step 2.2.1: Obtain the moisture content of the soil at each depth , the moisture content Available through survey reports.

[0052] Step 2.2.2: According to moisture content and strain variables Determine the density effect For example, the density influence Determine according to formula (3):

[0053] (3)

[0054] In the formula, is the strain variable; is the moisture content.

[0055] Step 2.2.3: According to the original density and density effect The quotient of the ramming density of the soil at each depth during the ramming process is determined , as shown in formula (4):

[0056] (4)

[0057] In the formula, is the original density; is the moisture content; is the stress variable; is the compression modulus.

[0058] Step 3: According to the tamping density and the maximum dry density of the soil at the corresponding depth Estimate the impact depth, including:

[0059] Step 3.1: According to the tamping density and the maximum dry density of the soil at the corresponding depth Determine the compaction coefficient of the soil at each depth , specifically including:

[0060] Step 3.1.1: Based on the wet density of the soil at each depth and relative density Determine the maximum dry density of soil , 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 ​​can be obtained from the survey report.

[0063] Step 3.1.2: According to the tamping density and the maximum dry density of the soil at the corresponding depth The compaction coefficient of the soil at each depth is determined by the quotient of , specifically:

[0064] (6)

[0065] Step 3.2: According to the compression coefficient Estimate the impact depth, including:

[0066] Step 3.2.1. Select a compression factor greater than a preset threshold as the first compression factor.

[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 soil to loosen after tamping, so in the process of determining the tamping depth, it will not cause sampling disturbance, test disturbance and other problems. The present invention is applicable to the tamping depth estimation of various soil types, especially to collapsible loess, which has a certain structure.

[0070] The present invention can obtain the compaction coefficient of soil at different depths of the foundation only by testing the horizontal stress at different depths, and then judge 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 intuitively determine whether the engineering quality meets the standard. The method of the present invention is simple to calculate, has clear mechanical concepts, high calculation accuracy, and wide applicability, and can avoid engineering risks caused by insufficient tamping depth.

[0072] The above are only several embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, using the above disclosed technical content to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for estimating tamping depth, characterized in that: include: Step 1, obtaining the original density, original stress and tamping stress of the soil at each depth of multiple depths at a preset horizontal distance from the tamping point; Step 2, determining the tamping density of the soil at each depth during the tamping process according to the original density, original stress and tamping stress; Step 3: Estimate the tamping depth according to the tamping density and the maximum dry density of the soil at the corresponding depth.

2. The ramming depth estimation method according to claim 1, characterized in that: Step 2 specifically includes: Determining a strain variable according to a difference between the impact stress and the original stress; The compaction density of the soil at each depth during the compaction process is determined according to the strain variable and the original density.

3. The ramming depth estimation method according to claim 2, characterized in that: 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: Get the moisture content of the soil at each depth; Determining a density influence amount according to the moisture content and the strain variable; The compaction density of the soil at each depth during the compaction process is determined according to the quotient of the original density and the density influence quantity.

4. The method for estimating the ramming depth according to claim 2, characterized in that: Determining the strain variable according to the difference between the impact stress and the original stress specifically includes: Determining a stress variable according to a difference between the impact stress and the original stress; The strain variable is determined based on the quotient of the stress variable and the compression modulus of the soil.

5. The ramming depth estimation method according to claim 1, characterized in that: Step 3 specifically includes: 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; The tamping depth is estimated based on the compaction factor.

6. The ramming depth estimation method according to claim 5, characterized in that: 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: Determine the maximum dry density of the soil based on the wet density and relative density of the soil at each depth; The compaction coefficient of the soil at each depth is determined based on the quotient of the tamping density and the maximum dry density of the soil at the corresponding depth.

7. The ramming depth estimation method according to claim 5, characterized in that: The tamping depth is estimated according to the compaction coefficient, specifically including: Selecting a compression coefficient greater than a preset threshold as the first compression coefficient; Determine the depth value corresponding to the first compaction coefficient, and take the maximum depth value as the tamping depth.

8. The method for estimating the ramming depth according to claim 1, characterized in that: The original stress of the soil at each depth is determined based on the lateral pressure coefficient, bulk density and depth of the soil.

9. The method for estimating the ramming depth according to claim 8, characterized in that: The lateral pressure coefficient is determined according to the internal friction angle of the soil.

10. The ramming depth estimation method according to claim 1, characterized in that: The preset horizontal distance is 3m~5m.

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