Visual detection method for rapidly detecting additional stress of foundation soil body

Abstract

The invention discloses a visual detection method for quickly detecting additional stress of a foundation soil body. The visual detection method comprises the following steps: loading the foundation soil body required by a test into a model box; in the process of filling the foundation soil body, the bags are arranged at the corresponding positions of the foundation soil body, and each bag is connected with each pressure measuring module; the independent foundation is placed above the foundation soil body, and it is guaranteed that the center point of the bottom of the independent foundation is aligned with the vertically-arranged bag; the force applying device applies a vertical load to the center point of the top of the independent foundation, and the additional stress of each position in the foundation soil body is detected through the pressure measuring device, so that the magnitude and the distribution range of the additional stress of the foundation soil body are obtained; and according to the magnitude and the distribution range of the additional stress of the foundation soil body, the spread angle of the additional stress of the foundation soil body is calculated. According to the visual detection method, the size, the distribution range and the spread angle of the additional stress of the foundation soil body can be simply and quickly obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of testing additional stress of foundation soil, and particularly relates to a visual detection method for quickly detecting the additional stress of foundation soil. Background Art

[0002] Additional stress refers to the stress increment generated in the foundation soil when the upper foundation is subjected to external loads, which is the main cause of foundation deformation, and additional stress only exists within the diffusion angle θ range. Therefore, it is necessary to study the additional stress and its specific parameters, which is beneficial to ensuring the safety and stability of the foundation in actual projects. The research on the additional stress of foundation soil mainly includes the following two aspects: one is the distribution range of the additional stress of foundation soil, and the other is the determination of the diffusion angle θ. If it is possible to achieve real-time dynamic visual observation of the water head height / additional stress (distribution range, diffusion angle θ) through naked-eye observation and with the help of computer equipment, it will bring great convenience to the research and teaching of the additional stress of foundation soil; however, there is currently no dynamic visual test device and method for quantitatively testing the distribution range of additional stress and the diffusion angle of additional stress. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a visual detection method for quickly detecting the additional stress of foundation soil, and the visual detection method can simply and quickly obtain the magnitude, distribution range and diffusion angle of the additional stress of foundation soil.

[0004] The technical solution of the present invention to solve the above technical problems is:

[0005] A visual detection method for quickly detecting the additional stress of foundation soil, comprising the following steps:

[0006] S1: Load the foundation soil required for the test into the model box; during the process of loading the foundation soil, arrange the bladder bags at the corresponding positions of the foundation soil, and connect each bladder bag to each pressure measurement module;

[0007] S2: Place the isolated foundation above the foundation soil, and ensure that the center point at the bottom of the isolated foundation is aligned with the vertically arranged bladder bag;

[0008] S3: The force application device applies a vertical load to the center point at the top of the isolated foundation, and detects the additional stress at each position in the foundation soil through the pressure measurement device, so as to obtain the distribution range of the additional stress of the foundation soil;

[0009] S4: Calculate the diffusion angle of the additional stress of the foundation soil according to the distribution range of the additional stress of the foundation soil.

[0010] Preferably, in step S1, there are multiple groups of the sacs, which are arranged below the isolated foundation and arranged along the length and / or height direction of the model box; there are multiple groups of the pressure measurement modules, and each group of the pressure measurement modules is connected to a group of the sacs.

[0011] Preferably, in step S1, multiple groups of the sacs respectively form a first sac layer, a second sac layer and a third sac layer. Among them, the first sac layer is located above the second sac layer and below the isolated foundation; multiple groups of the sacs in the first sac layer are arranged at equal intervals along the length direction of the model box; the second sac layer is located at the junction of the bearing layer and the soft subsoil layer in the foundation soil, and multiple groups of the sacs in the second sac layer are arranged at equal intervals along the length direction of the model box; the third sac layer is located below the center point at the bottom of the isolated foundation and is arranged at equal intervals along the height direction of the model box.

[0012] Preferably, in step S1, the distance between two adjacent groups of the sacs in the first sac layer, the second sac layer and the third sac layer is 20 cm.

[0013] Preferably, in step S1, the pressure measurement module is a piezometer tube, in which a water column is arranged, and a scale is arranged outside the piezometer tube; when the force application device applies a vertical load to the isolated foundation, the gas in the sacs causes the water column in the piezometer tube to rise.

[0014] Preferably, in step S1, a pore pressure sensor is arranged at the connection part between the piezometer tube and the sac; the pore pressure sensor is connected to a computer device.

[0015] Preferably, the force application device includes a support frame arranged on the model box and a jack arranged on the support frame. Among them, the support frame includes profiled steel columns arranged around the model box; two profiled steel columns on the left are connected by a first steel plate; two profiled steel columns on the right are connected by a second steel plate; the first steel plate and the second steel plate are connected by two groups of reaction cross beams; the two groups of reaction cross beams are arranged in parallel; the jack is installed on the two groups of reaction cross beams, and the output shaft of the jack is directly above the center point at the top of the isolated foundation.

[0016] Preferably, a pressure sensor is installed on the jack, and the pressure sensor is used to detect the magnitude of the vertical load applied by the jack.

[0017] Preferably, in step S3, the change value of the head height is obtained by observing the change in the height of the water column in the piezometer tube; the first product between the unit weight of the water column in the piezometer tube and the observed change value of the head height is calculated to obtain the pore water pressure in the piezometer tube, which is used as the additional pressure of the foundation soil at this position.

[0018] Preferably, in step S4, the second product of the difference between the distribution range of the additional pressure of the foundation soil and the bottom length of the isolated foundation and twice the distance between the bottom surface of the isolated foundation and the top surface of the soft underlying layer in the foundation soil is calculated, and the arctangent value of the ratio of the difference and the second product is obtained to obtain the diffusion angle of the additional stress of the foundation soil.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. The visual inspection method for quickly detecting the additional stress of the foundation soil of the present invention can quickly detect the magnitude, distribution range and diffusion angle of the additional pressure of the foundation soil. During the detection process, complex detection instruments / equipment are not required, and complex mathematical calculation models are not required either. The magnitude, distribution range and diffusion angle of the additional pressure of the foundation soil can be quickly obtained. This is especially applicable to some places lacking advanced detection instruments / equipment.

[0021] 2. The visual inspection method for quickly detecting the additional stress of the foundation soil of the present invention has low requirements for the properties, hardness, etc. of the foundation soil, can be applied to various types of foundation soils, and has the advantages of simple operation and low implementation cost.

[0022] 3. The visual inspection method for quickly detecting the additional stress of the foundation soil of the present invention allows the inspectors to observe the readings in the pressure measuring device with the naked eye, so as to quickly obtain the magnitude and distribution range of the additional stress at each position in the foundation soil, and the diffusion angle can be obtained through simple mathematical calculations. This has low requirements for the professional ability of the inspectors, that is, the inspectors do not need to have too much professional knowledge and the operation ability of the detection equipment / computer, and can also quickly obtain the magnitude, distribution range and diffusion angle of the additional pressure of the foundation soil through the visual inspection method of the present invention. Therefore, the visual inspection method of the present invention is suitable for large-scale popularization and use.

[0023] 4. The detection mechanism of the visual inspection method for quickly detecting the additional stress of the foundation soil of the present invention is simple, easy to operate and does not completely rely on professionals; it has low requirements for the properties, hardness, etc. of the foundation soil and can be applied to various types of foundation soils; the inspectors can conveniently and directly obtain simple and easy-to-understand visual results through naked-eye observation, which saves both the test cost and human resources. Brief Description of the Drawings

[0024] Figure 1 It is a schematic flow chart of the visualization detection method for quickly detecting the additional stress of foundation soil in the present invention.

[0025] Figure 2 It is a schematic diagram of the principle for calculating the diffusion angle of the additional stress of foundation soil.

[0026] Figure 3 It is a schematic structural diagram of the visualization test device for the additional stress of foundation soil in the present invention.

[0027] Figure 4 It is a schematic layout diagram of the bladder bags.

[0028] In the figure: 1 - model box; 11 - support frame; 2 - jack; 3 - isolated foundation; 4 - bladder bag; 5 - piezometer tube. Detailed Embodiment

[0029] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0030] Embodiment 1

[0031] Refer to Figures 1 - 4 , the visualization test device for the additional stress of foundation soil in the present invention includes a model box, foundation soil arranged in the model box, an isolated foundation, a force application device for applying a vertical load to the isolated foundation, and a detection device for detecting the additional stress in the foundation soil.

[0032] In this embodiment, the length × width × height of the bottom of the model box is 4m × 3m × 2m; the length × width of the bottom of the isolated foundation is 2m × 1.5m.

[0033] Refer to Figures 1 - 4, the detection device includes a bladder and a pressure measurement module connected to the bladder; wherein, there are multiple groups of bladders, and the multiple groups of bladders are arranged below the independent foundation and along the length and / or height direction of the model box; there are multiple groups of pressure measurement modules, and each group of pressure measurement modules is connected to a group of bladders; the pressure measurement module is a pressure measurement pipe, and the model box is provided with an avoidance hole for avoiding the pressure measurement pipe; the avoidance hole is arranged on one of the side surfaces of the model box; the inlet of the pressure measurement pipe is communicated with the bladder; in this embodiment, a water column is arranged in the pressure measurement pipe, and a scale is arranged outside the pressure measurement pipe; when the force application device applies a vertical load to the independent foundation, the gas in the bladder causes the water column in the pressure measurement pipe to rise; by observing the water head height of the pressure measurement pipe, the change value of the water head height can be obtained; by calculating the product of the specific weight of the water column in the pressure measurement pipe and the change value of the observed water head height, the pore water pressure in the pressure measurement pipe can be calculated, which is used as the additional pressure of the foundation soil at this position; by observing the change values of the water head heights in each pressure measurement pipe, the distribution range of the additional pressure of the foundation soil can be determined.

[0034] See Figures 1 - 4 , multiple groups of bladders respectively form a first bladder layer, a second bladder layer and a third bladder layer, wherein,

[0035] The first bladder layer is located above the second bladder layer and below the independent foundation; the multiple groups of bladders in the first bladder layer are arranged at equal intervals along the length direction of the model box; by installing bladders and pressure measurement pipes on the bottom surface of the independent foundation, after the independent foundation is subjected to a vertical load, the magnitude and distribution range of the pressure at the bottom of the independent foundation can be quantitatively measured, and the average pressure at the bottom of the independent foundation can be calculated therefrom.

[0036] The second bladder layer is located at the junction of the bearing layer and the soft underlying layer of the foundation soil, and the multiple groups of bladders in the second bladder layer are arranged at equal intervals along the length direction of the model box;

[0037] The third bladder layer is located below the center point at the bottom of the independent foundation and is arranged at equal intervals along the height direction of the model box; by setting the third bladder layer, it can be used to detect the distribution range of the additional pressure of the foundation soil in the vertical direction, that is, to detect whether there is additional pressure distribution at different depths of the foundation soil;

[0038] In this embodiment, the distance between adjacent two groups of bladders in the first bladder layer, the second bladder layer and the third bladder layer is 20 cm.

[0039] See Figures 1 - 4, the force application device includes a support frame disposed on the model box and a jack disposed on the support frame. Among them, the support frame includes steel columns disposed around the model box; two steel columns on the left side are connected by a first steel plate; two steel columns on the right side are connected by a second steel plate; the first steel plate and the second steel plate are connected by two groups of reaction cross beams; the two groups of reaction cross beams are arranged in parallel; the jack is installed on the two groups of reaction cross beams, and the output shaft of the jack is directly above the top center point of the isolated foundation; a vertical load of 0-10 KN can be applied to the top center point of the isolated foundation through the jack; a pressure controller can be installed on the jack, and the pressure controller can control the magnitude of the load applied by the jack.

[0040] In this embodiment, the support frame is welded to the outside of the model box, and the model box is made of light steel structure material; the height of the steel column is 4m.

[0041] See Figures 1 - 4 , the visualization detection method for quickly detecting the additional stress of foundation soil in the present invention includes the following steps:

[0042] S1: Load the foundation soil required for the test into the model box; during the process of loading the foundation soil, arrange the bladder bags at the corresponding positions of the foundation soil, and connect each bladder bag to each piezometric module;

[0043] S2: Place the isolated foundation above the foundation soil, and ensure that the center point at the bottom of the isolated foundation is aligned with the vertically arranged bladder bag;

[0044] S3: The force application device applies a vertical load to the center point at the top of the isolated foundation, and detects the additional stress at each position of the foundation soil through the piezometric device, so as to obtain the distribution range of the additional stress of the foundation soil; specifically;

[0045] By observing the change in the height of the water column in the piezometric tube, the change value h of the water head height is obtained; through the specific weight γ of the water column in the piezometric tube w and the observed change value h of the water head height, calculate the pore water pressure in the piezometric tube as the additional pressure of the foundation soil at this position;

[0046] u = γ w h;

[0047] Through the above formula, the magnitude of the additional pressure of the foundation soil can be quickly calculated, and according to the change value h of the water head height in each piezometric tube, the distribution range of the additional pressure of the foundation soil can be quickly obtained. Among them, the higher the change value h of the water head height, the greater the additional stress corresponding to this position.

[0048] S4: Since additional stress only exists within the range of the diffusion angle θ, after obtaining the distribution range of the additional stress and determining the bottom size (known size) of the isolated foundation, the diffusion angle of the additional stress of the foundation soil can be calculated based on the distribution range of the additional stress of the foundation soil and in combination with the bottom size of the isolated foundation.

[0049]

[0050] In the formula: B is the distribution range of the additional stress, expressed in length units; b is the bottom length of the isolated foundation, and H is the distance from the bottom surface of the isolated foundation to the top surface of the soft underlying layer in the foundation soil.

[0051] For the traditional determination of the additional stress and the diffusion angle θ at the top surface of the soft underlying layer in the foundation soil, it is necessary to follow the specifications in the foundation engineering book. The determination formula for the additional stress is:

[0052]

[0053] In the formula: l and b are respectively the length and width of the bottom edge of the isolated foundation, p k is the average pressure at the bottom surface of the isolated foundation (which can be measured through the first bladder layer), σ c is the self-weight stress value of the soil at the bottom surface of the isolated foundation, z is the distance from the bottom surface of the isolated foundation to the top surface of the soft underlying layer in the foundation soil, θ is the diffusion angle, and the determination of the diffusion angle is shown in Table 1.

[0054] Table 1: Foundation pressure diffusion angle θ

[0055]

[0056] In the table: E s1 is the compression modulus of the upper layer of soil; E s2 is the compression modulus of the lower layer of soil, z is the distance from the bottom surface of the foundation to the top surface of the soft underlying layer, and b is the width of the bottom edge of the foundation.

[0057] By comparing the two, for the calculation method of the diffusion angle θ in the visual inspection method for rapid detection of the additional stress of the foundation soil of the present invention, it is simpler, has lower requirements for the professional ability of the inspectors, and is more suitable for popularization and use.

[0058] The structure of the visualization test device for the additional stress of foundation soil used in the visualization test method for quickly detecting the additional stress of foundation soil according to the present invention is simple, easy to install and operate, and has a low implementation cost. When detecting the additional pressure at various positions of the foundation soil, there is no need to rely on precision instruments and equipment, and the later maintenance is simple and the maintenance cost is low. It is particularly suitable for some areas or places with backward technology or lack of detection equipment. In this way, the detection cost and the later maintenance cost can be reduced. Secondly, the visualization test method of the present invention does not need to rely on complex detection instruments / equipment, and has low requirements for the professional ability of the detection personnel. Ordinary personnel only need to undergo simple training to start detecting the magnitude, distribution range and diffusion angle of the additional stress of the foundation soil. Therefore, the visualization test method for quickly detecting the additional stress of the foundation soil according to the present invention has a low starting difficulty and is thus convenient for popularization and use.

[0059] In this embodiment, for the depth of the junction between the bearing layer and the soft underlying layer of the foundation soil, it is necessary to determine the soil layer distribution through the exploration report of the foundation soil.

[0060] Embodiment 2

[0061] The difference between this embodiment and Embodiment 1 is that:

[0062] A pore pressure sensor is provided at the part where the piezometer tube is connected to the bladder bag; the pore pressure sensor is connected to a computer device; correspondingly, a pressure sensor is provided on the jack, and the pressure sensor is connected to the computer device, and the computer device is used to control the magnitude of the vertical load applied by the jack;

[0063] In this embodiment, the computer device collects the data of the pore pressure sensors at each piezometer tube, and then more quickly calculates the magnitude, distribution range and diffusion angle of the additional stress of the foundation soil through the calculation method in Embodiment 1.

[0064] The above is a preferred embodiment of the present invention, but the embodiments of the present invention are not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A visual detection method for rapid detection of additional stress in foundation soil, characterized in that: The following steps are involved: S1: Load the foundation soil required for the test into the model box; During the process of filling the foundation soil, the bladder bags are arranged at corresponding positions of the foundation soil, and each bladder bag is connected to each pressure measuring module; S2: Place the independent foundation on top of the foundation soil, and ensure that the center point of the bottom of the independent foundation is aligned with the vertically arranged bag; S3: The force-applying device applies a vertical load to the center point of the top of the independent foundation, and the additional stress at each position in the foundation soil is detected by the pressure measuring device, so as to obtain the distribution range of the additional stress in the foundation soil; S4: Calculate the diffusion angle of the additional stress of the foundation soil according to the distribution range of the additional stress of the foundation soil.

2. The visual detection method for rapid detection of additional stress in foundation soil according to claim 1, characterized in that: In step S1, the bags are in multiple groups, which are arranged below the independent foundation and along the length and / or height direction of the model box; the pressure measuring modules are in multiple groups, and each group of pressure measuring modules is connected to a group of bags.

3. The visual detection method for rapid detection of additional stress in foundation soil according to claim 2, characterized in that: In step S1, multiple groups of bags constitute a first bag layer, a second bag layer and a third bag layer respectively, wherein the first bag layer is located above the second bag layer and below the independent foundation; the multiple groups of bags in the first bag layer are equidistantly arranged along the length direction of the model box; the second bag layer is located at the junction of the bearing layer and the weak underlying layer in the foundation soil, and the multiple groups of bags in the second bag layer are equidistantly arranged along the length direction of the model box; the third bag layer is located below the center point of the bottom of the independent foundation and is equidistantly arranged along the height direction of the model box.

4. The visual detection method for rapid detection of additional stress in foundation soil according to claim 3, characterized in that: In step S1, the distance between two adjacent groups of pouches in the first pouch layer, the second pouch layer and the third pouch layer is 20 cm.

5. The visual detection method for rapid detection of additional stress in foundation soil according to claim 4, characterized in that: In step S1, the pressure measuring module is a pressure measuring tube, a water column is arranged inside the pressure measuring tube, and a scale is arranged outside the pressure measuring tube; when the force applying device applies a vertical load on the independent foundation, the gas in the bag causes the water column in the pressure measuring tube to rise.

6. The visual detection method for rapid detection of additional stress in foundation soil according to claim 5, characterized in that: In step S1, a pore pressure sensor is provided at the portion where the pressure measuring tube is connected to the bladder bag; the pore pressure sensor is connected to a computer device.

7. The visual detection method for rapid detection of additional stress in foundation soil according to claim 6, characterized in that: The force-applying device includes a support frame arranged on the model box and a jack arranged on the support frame, wherein the support frame includes steel columns arranged around the model box; the two steel columns located on the left are connected by a first steel plate; the two steel columns located on the right are connected by a second steel plate; the first steel plate and the second steel plate are connected by two groups of reaction beams; the two groups of reaction beams are arranged in parallel; the jack is installed on the two groups of reaction beams, and the output shaft of the jack is located directly above the center point of the top of the independent foundation.

8. The visual detection method for rapid detection of additional stress in foundation soil according to claim 7, characterized in that: A pressure sensor is installed on the jack, and the pressure sensor is used to detect the magnitude of the vertical load applied by the jack.

9. The visual detection method for rapid detection of additional stress in foundation soil according to claim 8, characterized in that: In step S3, the change in the water head height is obtained by observing the change in the height of the water column in the pressure measuring tube; the pore water pressure in the pressure measuring tube is obtained by calculating the first product between the weight of the water column in the pressure measuring tube and the observed change in the water head height, which serves as the additional pressure of the foundation soil at that location.

10. The visual detection method for rapid detection of additional stress in foundation soil according to claim 9, characterized in that: In step S4, the diffusion angle of the additional stress in the foundation soil is obtained by calculating the second product of the difference between the distribution range of the additional pressure of the foundation soil and the length of the bottom side of the independent foundation and twice the distance from the bottom surface of the independent foundation to the top surface of the weak underlying layer in the foundation soil, and by obtaining the arc tangent value of the ratio of the difference and the second product.

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