Device for monitoring horizontal soil pressure change of existing pile foundation and frictional resistance calculation method

Abstract

The invention discloses an existing pile foundation horizontal soil pressure change monitoring device and a frictional resistance calculation method, and the device comprises a machine body which comprises a conical tip located at the bottom and a hollow pipe; the hollow pipe is provided with a plurality of mounting holes, and each mounting hole is provided with an annular protrusion extending outwards. One end of the sensor is connected with the annular protrusion, the other end of the sensor is arranged in an inner cavity of the hollow pipe, and the tail of the sensor is connected with an elastic abutting device. The signal processing module and the pressure control module are mounted at the top end of the hollow pipe; the pressure control module is mounted at one end, far away from the conical tip, of the hollow pipe; the pressure control module is used for measuring the horizontal soil pressure change of the existing pile foundation; and the expandable sleeve is connected with the outer wall of the fuselage in a sleeving manner. The pile foundation stress change is accurately measured; the pile side friction resistance is calculated by adopting an accurate integration method and considering the nonlinear characteristic of a soil body, integration is carried out layer by layer, and the friction resistance distribution and the total side friction resistance of the pile foundation at different depths are obtained.

Description

Technical Field

[0001] This application relates to the field of stress measurement technology, specifically to a monitoring device for changes in horizontal soil pressure in existing pile foundations and a method for calculating skin friction. Background Technology

[0002] When constructing a new tunnel near existing pile foundations, especially in urban areas or regions with high groundwater levels, soil displacement, stress redistribution, and changes in groundwater levels may occur. These factors can all affect the skin friction of the existing pile foundations, thereby impacting their bearing capacity. Therefore, monitoring changes in the skin friction of existing pile foundations is crucial during the construction of a new tunnel.

[0003] Changes in pile foundation skin friction can reflect the interaction between the pile foundation and the surrounding soil, as well as the stability of the soil. By monitoring the skin friction of existing piles, the condition of the pile foundation can be monitored during tunnel construction, the impact of construction on the pile foundation can be assessed, potential problems such as soil settlement and reduced pile bearing capacity can be identified in a timely manner, and reasonable construction plans and emergency plans can be formulated to ensure safety during construction.

[0004] Currently, most existing pile foundation horizontal earth pressure change devices are installed on the pile foundation during pile foundation construction. The direction of stress change is relatively singular when using traditional monitoring devices, and they cannot make good contact with the soil, which cannot guarantee the accuracy and stability of data acquisition. Summary of the Invention

[0005] This invention addresses the above-mentioned problems by proposing a monitoring device for changes in horizontal earth pressure on existing pile foundations and a method for calculating frictional resistance. The aim is to monitor the horizontal pressure on existing pile foundations when constructing tunnels next to existing buildings, and to better monitor the changes in horizontal earth pressure in different directions of existing pile foundations, thereby improving the accuracy of the collected data.

[0006] To achieve the above objectives, the present invention provides a device for monitoring changes in horizontal earth pressure on existing pile foundations, comprising: The fuselage includes a tapered tip at the bottom and an outer hollow tube connected to the tapered tip; the hollow tube is provided with a plurality of mounting holes, each of which is provided with an outwardly extending annular protrusion; The sensor has one end connected to the annular protrusion and the other end placed inside the hollow tube. The tail of the sensor is connected to an elastic abutment device. A signal processing module is installed at the end of the hollow tube away from the conical tip. A pressure control module is installed at the end of the hollow tube away from the conical tip; the pressure control module is used to measure the changes in horizontal earth pressure of existing pile foundations. An expandable sleeve is provided, which is connected to the outer wall of the machine body and is expanded or retracted by a pressure medium.

[0007] Furthermore, the hollow tube is a cylindrical tube.

[0008] Furthermore, it includes a data transmission line connecting the signal processing module to the host computer.

[0009] Furthermore, the outer wall of the expandable sleeve is provided with threaded texture.

[0010] Furthermore, the sensor includes a support tube and a piezoelectric material disposed within the support tube; one end of the support tube is connected to the elastic abutment device, and that end is provided with a pressure control system and a data transmission wire.

[0011] Furthermore, the elastic abutment device is a spring.

[0012] Furthermore, the conical tip is a drill bit device.

[0013] This invention also provides a method for calculating the skin friction of existing pile foundations, applied to the aforementioned monitoring device for changes in horizontal earth pressure on existing pile foundations. The method includes the following steps: S1: Calibrate the sensor according to the environmental parameters; S2: The monitoring device for the change of horizontal earth pressure on the existing pile foundation shall be placed close to the sidewall of the existing pile foundation. In the horizontal direction, no less than three monitoring devices shall be placed on the side closer to the new tunnel and no less than one monitoring device shall be placed on the side farther away from the tunnel, forming a monitoring group; and the number of monitoring groups shall be set to multiple groups distributed along the length of the existing pile foundation. S3: Control the expansion of the expandable sleeve to press against the soil; zero out the initial stress value of the sensor; S4: Based on the stress data collected by the sensor at different depths in the soil, the stress data is converted into a continuous stress function using a multi-point interpolation method. The nonlinear characteristics of the soil are incorporated to reflect the nonlinear stress-strain relationship data under different loading conditions. The frictional resistance at each depth is accurately calculated by integrating layer by layer at different soil depths and then accumulated; or the calculation is performed without considering the time change.

[0014] Furthermore, the environmental parameters include known stress conditions and soil conditions.

[0015] Furthermore, the calculation of frictional resistance specifically includes: High-precision measurement of stress changes: using sensors at different depths The measured stress data is used to generate a high-precision stress distribution curve; Higher-order interpolation: This method uses multi-point interpolation to convert discrete stress data points into continuous stress functions. ; Nonlinear soil model: A nonlinear stress-strain model is used to describe the real behavior of soil. The main parameters are the friction angle and shear modulus of the soil, so as to reflect the nonlinear stress-strain relationship of the soil under different loading conditions. Integral method: based on stress function Based on the nonlinear characteristics of the soil, the pile side friction is calculated using the following integral formula: Correction to the formula for pile side friction: Layer-by-layer integration: Integrate the different depths of the pile foundation layer by layer, combine the characteristics of each soil layer, accurately calculate the frictional resistance at each depth, and accumulate these frictional resistances to obtain the total side frictional resistance of the pile. Where z is the depth, and the unit is meters; The stress at depth z is measured in Pascals; the friction angle is the friction angle between the soil and the pile foundation, representing the frictional characteristics of the soil on the sliding surface, and is measured in degrees; shear modulus. It is the shear modulus of soil, which represents the soil's resistance to shear deformation, and its unit is Pascal. It is the total skin friction of the pile, and the unit is Newtons; It is the pile side friction at depth z, and the unit is Pascal; This is the perimeter of the pile foundation at depth z, in meters; and These are the starting and ending depths of the pile, respectively, in meters; σ(z) is the soil stress at depth z, in Pascals; φ(z) is the soil friction angle at depth z, in degrees. It is the differential of the pile side contact area at depth z, in square meters; pile foundation perimeter. Multiply by depth differential ,Right now .

[0016] Compared with the prior art, the device for monitoring changes in horizontal earth pressure and the method for calculating friction resistance of existing pile foundations provided by the present invention have the characteristics of being able to have good contact with the soil and monitor stress changes from multiple angles, while accurately calculating the friction resistance at each depth and the total side friction resistance of the pile body. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the existing pile foundation horizontal earth pressure change monitoring device in this application.

[0018] Figure 2This is a schematic diagram of the sensor structure for the existing pile foundation horizontal earth pressure change monitoring device of this application.

[0019] Figure 3 This is a top view schematic diagram showing the layout of the existing pile foundation horizontal earth pressure change monitoring device around the pile foundation in this application. Detailed Implementation

[0020] 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 protection scope of the present invention. It is understood that the accompanying drawings are provided for reference and illustration only, and are not intended to limit the present invention. The connection relationships shown in the accompanying drawings are only for clear description and do not limit the connection method.

[0021] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component, or there may be an intervening component. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be noted that, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; as a mechanical connection or an electrical connection; or as a connection within two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0022] It should also be noted that in the description of this invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] Please refer to Figures 1-3 This embodiment provides a device for monitoring changes in horizontal earth pressure on existing pile foundations, including: The fuselage includes a tapered tip at the bottom and an outer hollow tube 4 connected to the tapered tip; the hollow tube 4 is provided with a plurality of mounting holes, each of which is provided with an outwardly extending annular protrusion; the annular protrusion is preferably a circular ring structure.

[0024] Sensor 3, one end of which is connected to the annular protrusion, and the other end is placed in the inner cavity of the hollow tube 4. The tail of sensor 3 is connected to an elastic abutment device 33. A signal processing module is installed at the end of the hollow tube away from the conical tip. After sensor 3 stabilizes in contact with the soil, and after preliminary processing, the signal processing module located on the top of the machine transmits the data signal collected by sensor 3. The transmitted signal is amplified and strengthened, and the signal is collected and digitized to accurately measure the stress change of the pile foundation. The pile side friction is calculated by using a precise integration method and considering the nonlinear characteristics of the soil. The friction is integrated layer by layer to obtain the distribution of friction at different depths of the pile foundation and the total side friction.

[0025] A pressure control module is installed at the end of the hollow tube 4 away from the conical tip; the pressure control module is used to measure the change in horizontal soil pressure of the existing pile foundation; the pressure control module is electrically connected to the expandable sleeve 6. An expandable sleeve 6 is connected to the outer wall of the machine body, and the expandable sleeve 6 is expanded or retracted by a pressure medium.

[0026] The expandable sleeve 6 is expanded or retracted by the air pressure or hydraulic system inside the machine body.

[0027] The signal processing module and the pressure control module 2 are both located at the top of the hollow tube 4.

[0028] Please refer to Figure 1 The hollow tube 4 is a cylindrical tube.

[0029] Please refer to Figure 1 This includes a data transmission line 1 that connects the signal processing module to the host computer.

[0030] After the pressure control module measures the change in horizontal earth pressure of the existing pile foundation, the signal is processed by the top signal processing module and then transmitted to the host computer via data transmission line 1.

[0031] Preferably, the outer wall of the expandable sleeve 6 is provided with threaded texture.

[0032] Please refer to Figure 2The sensor includes a support tube 34 and a piezoelectric material 35 disposed inside the support tube 34; one end of the support tube 34 is connected to the elastic abutment device 33, and the end is provided with a pressure control system 32 and a data transmission wire 31.

[0033] Please refer to Figure 3 The elastic abutment device 33 is a spring. In a preferred embodiment, the spring is miniaturized to reduce the size of the control device.

[0034] The sensor 3 extends out of the annular protrusion through a miniature spring and a pneumatic system.

[0035] Please refer to Figure 1 The conical tip is the drill bit device 5.

[0036] Because some pile foundations 8 are quite long and located deep underground, a drill bit device 5 is needed to drill out the predetermined position so that the corresponding sensors 3 can be deployed. For shallower detection points, the sensors are placed by directly drilling into the machine through the top handle (not shown) and the bottom drill bit device 5.

[0037] This invention also provides a method for calculating the skin friction of existing pile foundations, applied to the aforementioned monitoring device for changes in horizontal earth pressure on existing pile foundations. The method includes the following steps: S1: Calibrate the sensor according to the environmental parameters; Specifically, before use, the sensor is calibrated under known stress conditions to ensure an accurate correspondence between the output voltage and actual stress changes. Tests are then conducted under different soil conditions to evaluate the device's performance in practical applications, ensuring it can provide stable and reliable data in various soil layers.

[0038] S2: The monitoring device for the change of horizontal earth pressure on the existing pile foundation is placed close to the sidewall of the existing pile foundation 8. In the horizontal direction, no less than three monitoring devices 7 are placed near the side of the new tunnel, and no less than one monitoring device 7 is placed away from the tunnel, forming a monitoring group; and the number of monitoring groups is set to be multiple groups distributed along the length of the existing pile foundation 8. Specifically, based on the geological survey report, the specific monitoring location is determined, and the standard interface on the top of the monitoring device is connected to the drill bit device 5. For measuring points with shallow depths, the device is pushed into the soil using the operating handle on the top. For measuring points with deeper depths, the device is installed after drilling with the drill bit device 5.

[0039] S3: Control the expansion of the expandable sleeve. Specifically, by setting a pressure control module at the top of the device, the pressure system is adjusted in real time to make the expandable sleeve 6 expand and press against the soil, thereby increasing the contact area and pressure of the sensor 3, ensuring stable contact between the sensor and the soil, and the elastic contact device 32 at the tail of the internal sensor 3 provides the initial contact force; and the initial stress value of the sensor 3 is zeroed. Before using the existing pile foundation horizontal earth pressure change monitoring device, sensor 3 was calibrated under known stress conditions, and on-site tests were conducted under different soil conditions to evaluate the device's performance in actual application.

[0040] S4: Based on the stress data collected by the sensor at different depths in the soil, the stress data is converted into a continuous stress function using a multi-point interpolation method. The nonlinear characteristics of the soil are incorporated to reflect the nonlinear stress-strain relationship data under different loading conditions. The frictional resistance at each depth is accurately calculated by integrating layer by layer at different soil depths and then accumulated; or the calculation is performed without considering the time change.

[0041] Furthermore, the environmental parameters include known stress conditions and soil conditions.

[0042] Furthermore, the calculation of frictional resistance specifically includes: High-precision measurement of stress changes: using sensors at different depths The measured stress data is used to generate a high-precision stress distribution curve; Higher-order interpolation: This method uses multi-point interpolation to convert discrete stress data points into continuous stress functions. Multi-point interpolation methods include Lagrange interpolation or polynomial interpolation. Nonlinear soil model: A nonlinear stress-strain model is used to describe the real behavior of soil. The main parameters are the friction angle and shear modulus of the soil. The model more accurately reflects the nonlinear stress-strain relationship of soil under different loading conditions. Accurate Method for Calculating Friction Resistance - Integral Method: Based on Stress Function Based on the nonlinear characteristics of the soil, the pile side friction is calculated using the following integral formula: Correction to the formula for pile side friction: Layer-by-layer integration: Integrate layer by layer at different depths of the pile foundation, combine the characteristics of each soil layer, accurately calculate the frictional resistance at each depth, and accumulate these frictional resistances to obtain the total side frictional resistance of the pile. Where z is the depth, and the unit is meters; The stress at depth z is measured in Pascals; the friction angle is... It is the friction angle between the soil and the pile foundation, representing the frictional characteristics of the soil on the sliding surface, and is measured in degrees; shear modulus. It is the shear modulus of soil, which represents the soil's resistance to shear deformation, and its unit is Pascal. It is the total skin friction of the pile, and the unit is Newtons; It is the pile side friction at depth z, and the unit is Pascal; This is the perimeter of the pile foundation at depth z, in meters. and These are the starting and ending depths of the pile, respectively, in meters; σ(z) is the soil stress at depth z, in Pascals; φ(z) is the soil friction angle at depth z, in degrees. It is the differential of the pile side contact area at depth z, in square meters; the pile foundation perimeter is 8. Multiply by depth differential ,Right now .

[0043] The present invention provides a monitoring device for changes in horizontal earth pressure on existing pile foundations and a method for calculating skin friction. This solves the problems of traditional monitoring devices, which only monitor stress changes in a single direction and cannot achieve good contact with the soil, thus failing to guarantee the accuracy and stability of data acquisition. The monitoring device in the technical solution provided by this invention has the characteristics of good contact with the soil, multi-angle monitoring of stress changes, and can accurately calculate the skin friction at various depths and the total side skin friction of the pile.

[0044] In the specification and claims of this application, the terms "comprising / including" and "having / including" and variations thereof are used to specify the presence of the stated features, values, steps or components, but do not exclude the presence or addition of one or more other features, values, steps, components or combinations thereof.

[0045] Some features of the present invention are described in different embodiments for clarity; however, these features may also be described in combination in a single embodiment. Conversely, some features of the present invention are described only in a single embodiment for brevity; however, these features may also be described individually or in any suitable combination in different embodiments.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for monitoring changes in horizontal earth pressure on existing pile foundations, characterized in that, include: The fuselage includes a tapered tip at the bottom and an outer hollow tube (4) connected to the tapered tip; the hollow tube (4) is provided with a plurality of mounting holes, each of which is provided with an outwardly extending annular protrusion; Sensor (3), one end of which is connected to the annular protrusion and the other end is placed in the inner cavity of the hollow tube (4). The tail of the sensor (3) is connected to an elastic abutment device (33). A signal processing module is installed at the end of the hollow tube away from the conical tip. A pressure control module is installed at the end of the hollow tube (4) away from the conical tip; the pressure control module is used to measure the changes in horizontal soil pressure of existing pile foundations. An expandable sleeve (6) is connected to the outer wall of the machine body, and the expandable sleeve (6) is expanded or retracted by a pressure medium.

2. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, The hollow tube is a cylindrical tube.

3. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, Includes a data transmission line (1) connecting the signal processing module to the host computer.

4. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, The outer wall of the expandable sleeve (6) is provided with threaded texture.

5. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, The sensor includes a support tube (34) and a piezoelectric material (35) disposed in the support tube (34); one end of the support tube (34) is connected to the elastic abutment device (33), and the end is provided with a pressure control system (32) and a data transmission wire (31).

6. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, The elastic abutment device (33) is a spring.

7. The device for monitoring changes in horizontal earth pressure on existing pile foundations according to claim 1, characterized in that, The conical tip is a drill bit device (5).

8. A method for calculating the skin friction of existing pile foundations, characterized in that, The method, applied to the monitoring device for changes in horizontal earth pressure on existing pile foundations as described in any one of claims 1 to 7, comprises the following steps: S1: Calibrate the sensor according to the environmental parameters; S2: The monitoring device for the change of horizontal earth pressure on the existing pile foundation is placed close to the side wall of the existing pile foundation (8). In the horizontal direction, no less than three monitoring devices (7) are placed near the side of the new tunnel, and no less than one monitoring device (7) is placed away from the tunnel, forming a monitoring group; and the number of monitoring groups is set to be multiple groups distributed along the length of the existing pile foundation (8). S3: Control the expansion of the expandable sleeve to press against the soil; zero out the initial stress value of the sensor; S4: Based on the stress data collected by the sensor at different depths in the soil, the stress data is converted into a continuous stress function using a multi-point interpolation method. The nonlinear characteristics of the soil are incorporated to reflect the nonlinear stress-strain relationship data under different loading conditions. The frictional resistance at each depth is accurately calculated by integrating layer by layer at different soil depths and then accumulated; or the calculation is performed without considering the time change.

9. The method for calculating the skin friction of existing pile foundations according to claim 8, characterized in that, The environmental parameters include known stress conditions and soil conditions.

10. The method for calculating the skin friction of existing pile foundations according to claim 8, characterized in that, The calculation of frictional resistance specifically includes: High-precision measurement of stress changes: using sensors at different depths The measured stress data is used to generate a high-precision stress distribution curve; Higher-order interpolation: This method uses multi-point interpolation to convert discrete stress data points into continuous stress functions. ; Nonlinear soil model: A nonlinear stress-strain model is used to describe the real behavior of soil. The main parameters are the friction angle and shear modulus of the soil, so as to reflect the nonlinear stress-strain relationship of the soil under different loading conditions. Integral method: based on stress function Based on the nonlinear characteristics of the soil, the pile side friction is calculated using the following integral formula: Correction to the formula for pile side friction: Layer-by-layer integration: Integrate the different depths of the pile foundation (8) layer by layer, combine the characteristics of each soil layer, accurately calculate the frictional resistance at each depth, and accumulate these frictional resistances to obtain the total side frictional resistance of the pile body. Where z is the depth, and the unit is meters; The stress at depth z is measured in Pascals; the friction angle is the friction angle between the soil and the pile foundation (8), representing the frictional characteristics of the soil on the sliding surface, and is measured in degrees; shear modulus It is the shear modulus of soil, which represents the soil's resistance to shear deformation, and its unit is Pascal. It is the total skin friction of the pile, and the unit is Newtons; It is the pile side friction at depth z, and the unit is Pascal; It is the perimeter of the pile foundation (8) at depth z, in meters; and These are the starting and ending depths of the pile, respectively, in meters; σ(z) is the soil stress at depth z, in Pascals; φ(z) is the soil friction angle at depth z, in degrees. It is the differential of the pile side contact area at depth z, in square meters; pile foundation (8) perimeter Multiply by depth differential ,Right now .

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