Method for evaluating real-time bearing capacity of water-sensitive soil stratum pile foundation
By embedding humidity sensors and miniature pressure gauges around and at the pile tip, and combining this with the finite element method, soil humidity can be monitored in real time and the bearing capacity of the pile foundation can be evaluated. This solves the problems of real-time and continuous evaluation of the bearing capacity of pile foundations in water-sensitive soil strata, reduces testing costs, and improves safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-03-31
AI Technical Summary
Existing technologies make it difficult to achieve real-time and continuous monitoring and assessment of the bearing capacity of pile foundations in water-sensitive soil strata. As a result, the bearing capacity of pile foundations is greatly affected by environmental factors, and the testing costs are high and the cycle is long, which cannot meet the safety assessment needs throughout the entire life cycle of construction and operation.
By burying humidity sensors and miniature pressure gauges around and at the pile tip, the soil humidity is monitored in real time, and the relationship between soil moisture content and mechanical properties is constructed. Combined with the seepage-stress coupled finite element method, the bearing capacity of the pile foundation is evaluated, and an early warning threshold is set to trigger a safety alarm.
It enables real-time and accurate assessment of the bearing capacity of pile foundations in water-sensitive soil strata, reduces testing costs, decreases post-processing expenses, and improves the safety and economic benefits of pile foundations.
Smart Images
Figure CN121765801A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of foundation bearing capacity assessment, and particularly relates to a method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata. Background Technology
[0002] Pile foundations have advantages such as minimal construction disturbance, low cost, no environmental pollution, and outstanding bearing capacity, and are widely used in various engineering construction fields, especially in projects with poor soil conditions and those bearing huge loads. However, limitations in construction equipment, technology, and conditions restrict pile depth and diameter, making it difficult to guarantee their bearing capacity. Currently, local reinforcement methods are often used to improve bearing capacity; however, blindly adopting reinforcement measures when faced with potential insufficient bearing capacity, even if it meets the bearing requirements, often comes at a high cost. Furthermore, during structural service, the bearing capacity of pile foundations is significantly affected by environmental factors, especially in water-sensitive soil strata, particularly in collapsible loess strata, where the bearing capacity decreases significantly, randomly, and over time upon contact with water. Therefore, based on real-time monitoring results of the soil moisture content around the piles, and by inferring the distribution characteristics of the soil moisture state around the piles, it is of great significance to assess the real-time bearing capacity of pile foundations in water-sensitive soil strata.
[0003] Currently, the assessment of pile foundation bearing capacity in various soil strata often employs highly reliable direct testing methods (such as self-balancing static pressure pile foundation testing). While this method can obtain relatively accurate pile foundation bearing capacity indicators, it is costly, time-consuming, complex to operate, and cannot perform continuous testing. Given that the soil surrounding pile foundations is highly susceptible to environmental water erosion during construction and operation, and that time-varying water intrusion often causes random and discontinuous degradation of pile foundation bearing capacity, there is an urgent need to develop a method that can monitor the moisture content of the soil around the pile in real time and assess the pile foundation bearing performance based on the monitoring results. This method would meet the requirement of real-time bearing capacity assessment throughout the entire lifecycle of pile foundations from construction to operation, providing a technical approach for the safe service and scientific maintenance of pile foundations in water-sensitive soil strata. Summary of the Invention
[0004] This invention aims to provide a method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata, which can assess the bearing capacity of pile foundations in real time based on monitoring data from soil moisture sensors installed around and at the pile tip.
[0005] The present invention provides a method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata, comprising the following steps:
[0006] Step 1: Drill holes for the pile foundation, and use a diamond drill bit to dry drill micro-opening along the pile body on the side wall and end of the pile hole, and simultaneously install humidity sensors and miniature pressure gauges; correct the indoor relationship in real time through in-situ testing of PSH.
[0007] Step 2: Conduct tests on the environmental parameters and mechanical properties of soils with different moisture contents, introduce temperature compensation, obtain the cavity humidity w of soils with different moisture contents and the strength, elastic modulus, shear modulus and friction coefficient of standard test blocks, and construct the relationship between soil moisture content and environmental and mechanical properties.
[0008] Step 3: Considering the time-dependent strength reduction of collapsible loess when exposed to water, the strength conversion value is corrected using a strength reduction function; then, using a wireless data sensor that can continuously collect soil moisture in real time, the soil moisture around and at the pile end is collected, and the soil moisture content is calculated using the relationship between soil cavity moisture and water content.
[0009] Step 4: Based on the relationship between soil moisture content and soil standard test block strength, elastic modulus, shear modulus and friction coefficient, and using data collected by soil moisture sensors installed around and at the pile tip, calculate the real-time mechanical properties of the soil.
[0010] Step 5: Using the seepage-stress coupled finite element method, the bearing capacity of the pile foundation under different moisture contents of the soil around the pile is analyzed, and finally the calculation formula of soil moisture content-pile foundation bearing capacity is constructed.
[0011] Step 6: Based on the relationship between soil moisture content and environmental / mechanical indicators, collect data through a humidity sensor, calculate the soil moisture content around the pile, and evaluate the real-time bearing capacity of the pile foundation using the soil moisture content-pile bearing capacity calculation formula.
[0012] Furthermore, in step 1, the minimally invasive opening is filled with bentonite-cement grout, and the opening area is locally reinforced with grout. After 24 hours, the grout solidifies and the opening is sealed with an expansion sealing strip.
[0013] Furthermore, the installation of the miniature pressure gauge is as follows: the soil pressure sensor is fixed to the fixing plate inside the hole via the upper and lower connectors.
[0014] Furthermore, in step 1, according to standard DB61 / T 943-2014, the indoor and field micro pressure gauge readings psh are calculated using the formula psh. 现场 =psh 室内 The result is obtained by converting ×1.2 to 1.5.
[0015] Furthermore, in step 2, the temperature compensation formula is: w=0.01×(RH-0.5×ΔT), where ΔT is the difference between the ambient temperature and the standard temperature, as specified in GB / T 35464-2017; and RH is the humidity data monitored by the minimally invasive opening.
[0016] For unsaturated areas, the conversion of soil moisture content from moisture content measured by minimally invasive perforation monitoring should also consider the correction for unsaturated areas, i.e., the moisture content converted from moisture content needs to be multiplied by a reduction factor ψ. s=1-0.01×(s-30), where s is the suction force in kPa.
[0017] Furthermore, the corrected formula in step 3 is: f s(t) =f s0 ×e^(-kΔt), where Δt is the stabilization time of the water content of collapsible loess, determined by the monitoring results of a humidity sensor; k is a correction coefficient, which, according to GB 50025, is 0.1~0.3 based on Δt; e is a common natural number; f s0 f represents the in-situ actual value of the soil strength in the measurement area; s(t) These are the indoor test values for soil strength in the measurement area.
[0018] Furthermore, the pile foundation bearing capacity analysis in step 5 specifically involves: using COMSOL to simulate humidity diffusion when the pile spacing S = 3D~6D, and correcting the single pile bearing capacity formula to: Q uk Group = Q uk Single × [1-0.1×(n-1)×(S / D-3)], where n is the number of piles, see standard DB51 / T 2379-2017.
[0019] Furthermore, it also includes setting early warning thresholds. When the moisture content at the pile tip is greater than wp+5% or the daily increase is greater than 3%, a yellow warning is triggered: the bearing capacity is reduced by 20%; if it continues for more than 7 days, a red warning is triggered: work is suspended for inspection.
[0020] The beneficial technical effects of this invention compared to the prior art are as follows:
[0021] (1) It effectively solved the need for real-time continuous testing of pile foundations and completed the real-time accurate assessment of their bearing capacity.
[0022] (2) By using the correlation between soil moisture and water content at multiple points, the distribution characteristics of soil water content in the pile foundation range were obtained based on real-time soil moisture monitoring data, and the real-time bearing capacity level of the pile foundation was evaluated based on this, thus solving the problem of discontinuity in pile foundation testing.
[0023] (3) Based on the distribution characteristics of soil moisture content in the pile foundation and combined with the mechanical parameters of the soil in the stratum, numerical test results of pile foundation bearing capacity were obtained, overcoming the problems of high cost, long time consumption and inability to continuously test conventional pile foundations.
[0024] (4) The relationship between "soil moisture content - water content" and "soil water content - mechanical parameters" obtained by multi-sample regression analysis is scientifically sound and can reflect objective laws, providing reliable technical support for the real-time continuous assessment of the bearing capacity of water-sensitive soil foundation piles.
[0025] (5) The improved single-pile monitoring cost increases by 2,000 to 3,000 yuan (including pressure gauge and temperature compensation module), but can reduce the post-accident handling cost by 30% (according to statistics from Northwest Institute, the average loss of a sinkhole accident is 500,000 yuan / pile). Attached Figure Description
[0026] Figure 1 This is a schematic diagram of pile foundation drilling.
[0027] Figure 2 This is a schematic diagram of the sealing method for the installation hole of the humidity sensor on the side wall of the pile foundation.
[0028] Figure 3 This is a schematic diagram of the installation of a miniature pressure meter.
[0029] In the diagram, 1-Pile hole; 2-Minimally invasive opening; 3-Soil; 4-Expansion waterstop strip; 5-Humidity sensor; 6-Miniature pressure gauge; 7-Bentonite-cement grout; 8-Soil pressure sensor; 9-Upper connector; 10-Lower connector; 11-Fixing plate; 12-Local grouting reinforcement range of the opening area.
[0030] Figure 4 This is a flowchart illustrating the relationship between the humidity of water-sensitive soil cavities and the soil moisture content.
[0031] Figure 5 This is a flowchart illustrating the process of establishing the relationship between water content and mechanical parameters in water-sensitive soil.
[0032] Figure 6 This is a flowchart of the numerical test method for the bearing capacity of pile foundations in water-sensitive soil strata.
[0033] Figure 7 This is a schematic diagram of the method for assessing the bearing capacity of pile foundations in water-sensitive soil strata. Detailed Implementation
[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0035] It should be noted that the following detailed descriptions are illustrative examples intended to further illustrate this application. Unless otherwise specified, all technical terms, methods, and technical terms mentioned in this application have the same meaning as those used in the same field.
[0036] The present invention provides a method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata, comprising the following steps:
[0037] Step 1: Drilling holes for pile foundations, such as... Figure 1 As shown, along the pile body, a φ12mm diamond drill bit was used to dry drill a micro-invasive hole 2 on the side wall and end of pile hole 1 (to make the disturbance area <10cm), as follows. Figure 2 As shown, a humidity sensor 5 and a miniature pressure gauge 6 (such as a PIP) are simultaneously installed.
[0038] The minimally invasive opening 2 was filled with bentonite-cement grout 7 (1:3 ratio), and the opening area was locally reinforced with grout. After 24 hours, the grout solidified, and the opening was sealed with an expansion sealing strip 4. The installation of the miniature pressure gauge 6 was as follows. Figure 3 As shown, specifically, the soil pressure sensor 8 is fixed to the fixing plate 11 inside the hole via the upper connector 9 and the lower connector 10.
[0039] Considering that the opening in the sidewall of the pile hole disrupts the large pore structure of the loess, resulting in an "artificial weak zone" around the sensor and causing the measured humidity to be higher than the true value, the indoor relationship is corrected in real time by in-situ testing of psh. According to the standard DB61 / T 943-2014, the indoor and field micro pressure meter (PIP) reading psh is calculated using the formula psh. 现场 =psh 室内 The result is obtained by multiplying by 1.2 to 1.5, such as... Figure 5 As shown.
[0040] Step 2: Conduct tests on the environmental parameters and mechanical properties of soils with different moisture contents, introduce temperature compensation, obtain the cavity humidity w of soils with different moisture contents and the strength, elastic modulus, shear modulus and friction coefficient of standard test blocks, and construct the relationship between soil moisture content and environmental and mechanical properties.
[0041] The relationship between the cavity moisture content and soil water content of collapsible loess was constructed as follows: Figure 4 As shown, the temperature compensation formula is: w=0.01×(RH-0.5×ΔT), where ΔT is the difference between the ambient temperature and the standard temperature (20℃), see standard GB / T 35464-2017; RH is the humidity data monitored by the minimally invasive opening.
[0042] For unsaturated areas, the conversion of soil moisture content from moisture content measured by minimally invasive perforation monitoring should also consider the correction for unsaturated areas, i.e., the moisture content converted from moisture content needs to be multiplied by a reduction factor ψ. s =1-0.01×(s-30), where s is the suction force in kPa (according to Cauchy's law).
[0043] Step 3: Considering the time-dependent strength reduction of collapsible loess when exposed to water, the strength conversion value is corrected using a strength reduction function; then, using a wireless data sensor that can continuously collect soil moisture in real time, the soil moisture around and at the pile end is collected, and the soil moisture content is calculated using the relationship between soil cavity moisture and water content.
[0044] The relationship between water content and mechanical parameters of collapsible loess is constructed as follows: Figure 5 As shown, considering the time-dependent softening of the soil in the field (collapse deformation takes 7-14 days to complete), and the inability of real-time sensor data (such as instantaneous humidity) to reflect the strength decay process, the correction formula is: f s(t) =fs0 ×e^(-kΔt), where Δt is the stabilization time of the water content of collapsible loess, determined by the monitoring results of a humidity sensor; k is a correction coefficient, which, according to GB 50025, is 0.1~0.3 based on Δt; e is a common natural number; f s0 f represents the in-situ actual value of the soil strength in the measurement area; s(t) These are the indoor test values for soil strength in the measurement area.
[0045] Step 4: Based on the relationship between soil moisture content and soil standard test block strength, elastic modulus, shear modulus and friction coefficient, and using data collected by soil moisture sensors installed around and at the pile tip, calculate the real-time mechanical properties of the soil.
[0046] Step 5: Using the seepage-stress coupled finite element method, the bearing capacity of the pile foundation under different moisture contents of the soil around the pile is analyzed, and finally the calculation formula of soil moisture content-pile foundation bearing capacity is constructed.
[0047] Pile foundation bearing capacity analysis as follows Figure 6 As shown, specifically: using COMSOL to simulate humidity diffusion when the pile spacing S = 3D~6D, the formula for single pile bearing capacity is corrected to: Q uk Group = Q uk Single × [1-0.1×(n-1)×(S / D-3)], where n is the number of piles, see standard DB51 / T 2379-2017.
[0048] Step 6: Based on the relationship between soil moisture content and environmental / mechanical indicators, collect data through a humidity sensor, calculate the soil moisture content around the pile, and evaluate the real-time bearing capacity of the pile foundation using the soil moisture content-pile bearing capacity calculation formula.
[0049] Set an early warning threshold. When the moisture content at the pile tip is greater than wp+5% (wp is the plastic limit) or the daily increase is greater than 3%, a yellow warning is triggered: the bearing capacity is reduced by 20%; if it continues for more than 7 days, a red warning is triggered: work is suspended for inspection.
[0050] In a preferred embodiment: the sensor hole for collecting soil moisture has good waterproof and effective air permeability, which prevents water seepage and ensures that humid air can effectively diffuse into the detection hole, ensuring that the air humidity in the detection cavity is positively correlated with the moisture content of the adjacent soil.
[0051] In a preferred embodiment: the sensor used to collect the humidity of the soil cavity around the pile foundation has sufficient accuracy and good durability, and can continuously and effectively transmit the detection signal. A high-performance wireless sensing device is preferred.
[0052] In a preferred embodiment, the relationship between soil cavity moisture and its water content should be supported by sufficient data to ensure reliable accuracy; the relationship between soil water content and soil mechanical properties should be supported by sufficient experimental data to ensure reliable accuracy. Furthermore, all relationships should be constructed using a fitting method with minimal error.
[0053] In a preferred embodiment, when conducting finite element analysis of pile foundations in soil strata with different moisture contents, the range of values for soil moisture content calculation examples, the frequency domain of samples, and the distribution form should include the control state of the actual pile foundation service environment, that is, the working conditions that may occur under the normal service state of the pile foundation, so as to ensure that the finite element analysis results can include all actual bearing states of the in-service pile foundation.
[0054] In a preferred embodiment, the data acquisition device for soil moisture sensors within the pile foundation area should be equipped with multiple channels, capable of simultaneously acquiring and transmitting multi-channel data, and able to work online with a terminal analysis computer to achieve simultaneous acquisition, conversion, and transmission of environmental parameters of multiple points around a single pile, as well as real-time assessment of the pile foundation bearing capacity.
[0055] In a preferred embodiment, the method for real-time bearing capacity assessment of collapsible loess pile foundations is as follows: Figure 7 As shown, specifically:
[0056] Step S1: Using various automatic and manual drilling methods for pile foundations, complete the excavation of the pile foundation soil, and over-excavate holes at the designed locations on the pile side and pile end for burying humidity sensing equipment.
[0057] Step S2: Install wired or wireless humidity sensing equipment and adjust it to meet the signal strength and stability requirements. Use waterproof material to reliably seal the equipment opening. Ensure that groundwater cannot seep into the equipment opening and that the vaporized moisture inside and outside the equipment opening is fully convected.
[0058] Step S3: Use the humidity sensing device embedded in the monitoring hole at the pile side and pile end to continuously monitor the soil humidity (M′) at the monitoring point, and collect and store the monitoring data through a wired or wireless receiving platform.
[0059] Step S4: Conduct statistical measurements of the humidity of the internal pore walls of soil test blocks with different moisture contents, plot the humidity change curves of the internal pores of soil test blocks with different moisture contents under different size conditions, determine the stable humidity values of soil test blocks of different sizes under different moisture contents, plot the scatter plot of soil moisture content (W) and its stable humidity value (M), compare the errors of the soil moisture content and stable humidity value curves (W-M curves) fitted by different methods, and use the minimum error curve to regress its functional expression (W-M relationship).
[0060] Step S5: Conduct compressive, shear, and triaxial tests on soil specimens with different moisture contents. Based on the relationship between soil moisture content and cavity humidity, plot a scatter plot of soil cavity humidity and parameters such as soil strength, internal friction angle, shear modulus, elastic modulus, cohesion, and friction coefficient. Use different methods to plot the relationship curves between the stable value of soil cavity humidity and physical and mechanical parameters, compare the error levels of each fitted curve, and then, based on the relationship curve with the minimum error, regress to obtain the functional expression (M~K) of the stable value of soil cavity humidity (M) and physical and mechanical parameters ([K]).
[0061] Step S6: Construct a three-dimensional finite element model of the pile foundation at a constant scale. Divide the stratum model into several unit layers. Pile foundation parameters such as pile diameter and pile length are input using a parameter input mode. A parametric approach is used to achieve rapid finite element modeling of the pile foundation and its surrounding stratum. Analyze the pile foundation bearing capacity under different parameter combinations, plot their relationship curves, fit the relationship between soil moisture and bearing capacity for different soil samples, and use the variance contribution method to obtain the weight of the influence of soil moisture levels at different locations around the pile foundation on the pile foundation bearing capacity. Construct a pile foundation bearing capacity calculation model based on soil moisture.
[0062] Step S7: Based on the soil moisture measurement value M′ around the pile foundation monitored in Step S3, calculate the pile foundation bearing capacity according to the pile foundation bearing capacity calculation model constructed in Step S6.
[0063] It should be clarified that the technologies, methods and technical terms described herein are used only in the specific implementation of this application and are not limited to the embodiments.
Claims
1. A method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata, characterized in that, Includes the following steps: Step 1: Drill holes for the pile foundation, and use a diamond drill bit to dry drill micro-opening (2) along the pile body on the side wall and end of the pile hole (1), and simultaneously install a humidity sensor (5) and a miniature pressure meter (6); correct the indoor relationship in real time through in-situ testing of psh; Step 2: Conduct tests on the environmental parameters and mechanical properties of soils with different moisture contents, introduce temperature compensation, obtain the cavity humidity w of soils with different moisture contents and the strength, elastic modulus, shear modulus and friction coefficient of standard test blocks, and construct the relationship between soil moisture content and environmental and mechanical properties. Step 3: Considering the time-dependent strength reduction of collapsible loess when exposed to water, the strength conversion value is corrected by the strength reduction function; then, a wireless data sensor capable of continuously collecting soil moisture in real time is used to collect the soil moisture around the pile and at the end, and the soil moisture content is calculated using the relationship between soil cavity moisture and water content. Step 4: Based on the relationship between soil moisture content and soil standard test block strength, elastic modulus, shear modulus and friction coefficient, and according to the data collected by soil moisture sensors installed around and at the pile end, calculate the real-time mechanical properties of the soil. Step 5: Using the seepage-stress coupled finite element method, the bearing capacity of the pile foundation under different moisture contents of the soil around the pile is analyzed, and finally the calculation formula of soil moisture content-pile foundation bearing capacity is constructed. Step 6: Based on the relationship between soil moisture content and environmental / mechanical indicators, collect data through a humidity sensor, calculate the soil moisture content around the pile, and evaluate the real-time bearing capacity of the pile foundation using the soil moisture content-pile bearing capacity calculation formula.
2. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, In step 1, the minimally invasive opening (2) is filled with bentonite-cement grout (7), and the opening area is locally reinforced by grouting. After 24 hours, the grouting is solidified, and the opening is sealed with an expansion sealing strip (4).
3. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 2, characterized in that, The installation of the miniature pressure gauge (6) is as follows: the soil pressure sensor (8) is fixed to the fixing plate (11) inside the hole by the upper connector (9) and the lower connector (10).
4. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, In step 1, according to standard DB61 / T 943-2014, the indoor and field micro pressure gauge readings psh are calculated using the formula psh. 现场 =psh 室内 The result is obtained by converting ×1.2 to 1.
5.
5. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, In step 2, the temperature compensation formula is: w = 0.01 × (RH - 0.5 × ΔT), where ΔT is the difference between the ambient temperature and the standard temperature (see standard GB / T 35464-2017); RH is the humidity data monitored by the minimally invasive opening. For unsaturated areas, the conversion of soil moisture content from moisture content measured by minimally invasive perforation monitoring should also consider the correction for unsaturated areas, i.e., the moisture content converted from moisture content needs to be multiplied by a reduction factor ψ. s =1-0.01×(s-30), where s is the suction force in kPa.
6. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, The corrected formula in step 3 is: f s(t) =f s0 ×e^(-kΔt), where Δt is the stabilization time of the water content of collapsible loess, determined by the monitoring results of a humidity sensor; k is a correction coefficient, which, according to GB 50025, is 0.1~0.3 based on Δt; e is a common natural number; f s0 f represents the in-situ actual value of the soil strength in the measurement area; s(t) These are the indoor test values for soil strength in the measurement area.
7. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, The pile bearing capacity analysis in step 5 specifically involves: using COMSOL to simulate humidity diffusion when the pile spacing S = 3D~6D, and correcting the single pile bearing capacity formula as follows: Q uk Group = Q uk Single × [1-0.1×(n-1)×(S / D-3)], where n is the number of piles, see standard DB51 / T 2379-2017.
8. The method for real-time bearing capacity assessment of pile foundations in water-sensitive soil strata according to claim 1, characterized in that, It also includes setting early warning thresholds. When the moisture content at the pile tip is greater than wp+5% or the daily increase is greater than 3%, a yellow warning is triggered: the bearing capacity is reduced by 20%; if it continues for more than 7 days, a red warning is triggered: work is suspended for inspection.