Methods for Determining the Dangerous Slip Surface and Measuring the Stability of Crushed Stone Pile Composite Foundation Excavation

Abstract

This application belongs to the technical field of dangerous slip surface excavation, specifically involving a method for determining dangerous slip surface and measuring stability in the excavation of crushed stone pile composite foundation. This method can effectively overcome the limitations of standard regulations and traditional limit equilibrium methods, has a wide range of applications, and high accuracy. At the same time, the criteria used can accurately determine the stability state of the slope top and slope body at different stages during the excavation process, providing an effective basis for the prediction, forecasting, and treatment of foundation slopes.

Description

Technical Field

[0001] This application belongs to the technical field of excavation dangerous slip surface, specifically involving the method for determining the dangerous slip surface and measuring the stability of crushed stone pile composite foundation excavation. Background Technology

[0002] Crushed stone piles are composite foundation reinforcement piles made primarily of crushed stone or pebbles. They are suitable for compacting loose sand, silt, plain fill, and miscellaneous fill foundations, and are mainly used in geotechnical engineering fields such as soft foundations, dam slope reinforcement, and enhancing the bearing capacity of foundation soil. Crushed stone piles have a replacement and compaction effect on sand, silt, and crushed stone soil, while their replacement effect is mainly on cohesive soil and fill. With the expansion of coastal cities, the demand for land is increasing, and the development and utilization of coastal soft soil has become a new challenge in engineering construction. Coupled with the rapid development of high-rise buildings, highways, and railways, the requirements for foundation bearing capacity are also increasing. Due to the special physical properties and engineering characteristics of soft soil, it is prone to significant settlement, and even overall foundation instability, causing construction delays and even huge losses of life and property. Therefore, how to effectively monitor and warn of the stability of composite foundation slope excavation and unloading processes and minimize the resulting losses is an urgent priority in the field of disaster prevention and mitigation for foundation pit slopes in coastal cities.

[0003] In traditional construction processes, the stability of the foundation pit is mainly evaluated based on the displacement of the foundation slope or wall monitored on-site, according to specifications. An alarm is triggered when the displacement value exceeds the prescribed warning value. However, since each slope project has different slope types, safety levels, working conditions, surrounding environment, and engineering geological conditions, it is obviously unreasonable to use a uniform deformation control value. Often, the foundation slope deforms excessively without the foundation becoming unstable, or the foundation slope deforms but fails to exceed the deformation control value. In addition, the limit equilibrium method is also a commonly used method for slope stability analysis. It obtains the solution by analyzing the force balance of the soil at the moment of failure, with typical examples including the Swedish method and the Bishop simplified method. However, when calculating the slope stability safety factor, the limit equilibrium method simplifies many conditions, and the results may deviate significantly from the actual working conditions. The results are not accurate enough when the soil friction angle is large or the included arc angle of the sliding surface is large. Furthermore, the use of crushed stone piles alters the original sliding surface of the soil, making it unusable in the stability evaluation of soil slopes with weak layers in crushed stone pile composite foundations. Summary of the Invention

[0004] To overcome the shortcomings and limitations of the aforementioned methods for determining the stability of foundation slopes, this invention, based on the action mechanism and displacement dynamic action law of gravel pile composite foundation slopes, and after modifying the shear strength parameters of the composite foundation, proposes a dynamic load displacement response ratio prediction parameter and method that uses the excavation depth of the foundation slope as the dynamic load and the displacement caused by excavation as the dynamic response. This method can, to some extent, overcome the shortcomings and limitations of the aforementioned traditional foundation slope stability evaluation methods and has significant application value in the field of gravel pile composite foundation slope stability monitoring and determination.

[0005] A method for determining the dangerous slip surface during excavation of a composite foundation with crushed stone piles includes the following steps:

[0006] Step 1: Determine the cohesion C of the composite soil of the gravel pile composite foundation slope using in-situ geotechnical tests or laboratory geotechnical tests. c Internal friction angle of composite soil And determine the cohesion C of the crushed stone. g The internal friction angle of gravel

[0007] Step 2: Using formulas (1) and (2), and the measured shear strength parameters of the soil layer and the crushed stone piles on the slope of the composite foundation, the cohesion and internal friction angle of the composite soil are calculated. The slope of the composite foundation is regarded as a homogeneous rock and soil mass, and the most dangerous slip surface is calculated by the classical circular arc method.

[0008]

[0009]

[0010] In the formula: C c For the cohesion of composite soil, C g For the cohesive force of the crushed stone, C sc For the cohesion of the foundation, The internal friction angle of the composite soil. The internal friction angle of the gravel. denoted as the internal friction angle of the foundation, and m as the area replacement rate.

[0011] A method for determining the stability of a dangerous slip surface in the excavation of a crushed stone pile composite foundation, using the method of this application to determine the slip surface, and deformation monitoring including measuring the horizontal displacement at the top of the slope and the horizontal displacement of the slope body to reflect the stability state of the slope; including the following steps:

[0012] Step 3: Selection of slope excavation displacement monitoring points and installation and layout of monitoring equipment;

[0013] Step 4: Real-time monitoring and data processing of slope excavation depth and slope displacement;

[0014] Step 5: Determination of the dynamic load displacement response rate of composite foundation slope excavation;

[0015] Step Six: Determining the evaluation parameters for the dynamic load displacement response ratio of composite foundation slopes;

[0016] Step 7: Determination of the instability criterion for the slope dynamic loading displacement response ratio evaluation parameters;

[0017] Step 8: Determine and evaluate the stability of composite foundation slopes by comparing dynamic load displacement response.

[0018] Preferably, in step three, a high-performance vibrating wire displacement sensor is used to monitor the horizontal displacement of the slope. The number of monitoring points is one per L of the total excavation depth. At the same depth, the same number of displacement monitoring points are moved further into the slope. A distributed GPRS node wireless data acquisition system is used to collect the monitoring data.

[0019] Preferably, the depth of each excavation of the composite foundation slope and the resulting horizontal displacement response are monitored in real time. The horizontal displacement data is transmitted from each monitoring point to the host computer via the wireless acquisition device of the monitoring equipment. The excavation depth is obtained directly from the construction plan. The monitoring data is then preprocessed and entered into an Excel spreadsheet. The slope excavation depth is denoted as H. i The horizontal displacement caused by excavation is denoted as S. ni , where i represents the excavation stage and n represents the monitoring point number.

[0020] Preferably, in step five, during the excavation of the gravel pile composite foundation slope, excavation is the main dynamic factor affecting and controlling the slope displacement and stability. There is a one-to-one correspondence between the excavation depth and the slope displacement. Taking the initial excavation depth H1 of the slope as the initial load, the horizontal displacement S caused by the initial excavation... n1 As the initial displacement response, the initial dynamic load displacement response rate at the top of the slope can be calculated according to equation (3):

[0021]

[0022] The excavation depth of any subsequent excavation step on the slope is taken as the slope dynamic load H of that excavation step. i Horizontal displacement S caused by slope excavation ni As the displacement response of this excavation step, the dynamic load displacement response rate of any subsequent excavation step of the slope can be calculated according to equation (4):

[0023]

[0024] Preferably, in step six, the dynamic load displacement response rate λ under any subsequent excavation step of the slope is... niThe initial dynamic load displacement response rate λ of the slope n0 The ratio is defined as the slope dynamic load displacement response ratio for that excavation step. An evaluation model for the slope dynamic load displacement response ratio is established, namely:

[0025]

[0026] In the formula: ΔS n1 ΔS ni The horizontal displacement values ​​are H1 and H2 under the initial excavation step and subsequent excavation steps. i The dynamic load values ​​under the initial excavation step and subsequent excavation steps are used as the dynamic load displacement response ratio of the slope. Therefore, the stability evaluation parameter of the slope is used to predict and evaluate its stability.

[0027] Preferably, the safety factor K is defined as the ratio of the limit damage to the maximum allowable damage, that is:

[0028]

[0029] In the formula: D cr To allow for maximum damage, the limiting damage D im Set to 1; throughout the entire damage and failure process, the damage variable D i Gradually approaching D cr Therefore, the maximum safety factor K cr It can be represented as:

[0030]

[0031] The above formula shows that there is a one-to-one correspondence between the dynamic load displacement response ratio of the slope and the slope safety factor, that is, the dynamic load displacement response ratio parameter can be used to quantitatively evaluate the slope stability.

[0032]

[0033] When the displacement response ratio parameter η is increased by dynamic loading ni Less than or equal to η cr When the slope is in a stable state, it indicates that the slope is in a stable state; when the dynamic load displacement response ratio parameter η ni Greater than η cr This indicates that the slope is in an unstable state and there is a possibility of landslide.

[0034] Compared with the prior art, the beneficial effects of this application are as follows:

[0035] This method is simple to calculate and can analyze the action mechanism and displacement dynamic law of the slope of the crushed stone pile composite foundation. It has high accuracy and provides a new method for determining the excavation stability of the slope of the crushed stone pile composite foundation. Attached Figure Description

[0036] Figure 1 This is a flowchart of the process involved in the invention.

[0037] Figure 2 This is a schematic diagram of the layout of slope monitoring points and instruments.

[0038] Figure 3 This is a stress analysis diagram of the excavated slope blocks.

[0039] Figure 4 This is a diagram of the most dangerous slip surface of the slope. Detailed Implementation

[0040] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0041] A method for determining the excavation stability of a composite foundation slope with crushed stone piles includes the following steps:

[0042] Step 1: Exploration and determination of shear strength parameters of foundation slope;

[0043] The cohesion C of the composite soil of the gravel pile composite foundation slope was determined by comprehensively using in-situ soil and rock tests or laboratory geotechnical tests. c Internal friction angle of composite soil And determine the cohesion C of the crushed stone. g The internal friction angle of gravel

[0044] Step 2: Determining the most dangerous potential slip surface of the gravel pile composite foundation slope;

[0045] Based on principle 1, formulas (1) and (2), and the measured shear strength parameters of the soil layer and the crushed stone piles on the slope of the composite foundation of the crushed stone pile, the cohesion and internal friction angle of the composite soil are calculated. The slope of the composite foundation of the crushed stone pile is regarded as a homogeneous rock and soil body. The most dangerous sliding surface is calculated by the classical circular arc method. The characteristics such as the slope size and distribution range are analyzed to determine the main sliding zone of the slope.

[0046]

[0047]

[0048] In the formula: C c For the cohesion of composite soil, C g For the cohesive force of the crushed stone, C sc For the cohesion of the foundation, The internal friction angle of the composite soil. The internal friction angle of the gravel. denoted as the internal friction angle of the foundation, and m as the area replacement rate.

[0049] Principle 1 is as follows:

[0050] The area replacement rate method is based on the test strength of the crushed stone pile and the surrounding soft coastal soil under the same conditions, multiplied by the area ratio of each. Its disadvantage is that it does not take into account the interaction effect between the pile and the soil.

[0051] Cohesion of composite soil:

[0052] C c =mC g +(1-m)C sc (7)

[0053] Internal friction angle of composite soil:

[0054]

[0055] Due to the shear dilatation of the crushed stone material, the radial stress on the pile-soil interface is higher than the confining pressure. This indicates that the stress in the composite soil is not a simple combination of the stresses of the individual materials under the same test conditions according to the area replacement ratio. Factors such as the increase in pile confining pressure after the lateral interaction between the pile and the soil should be considered. Therefore, the pile confining pressure in the composite soil was corrected, and the pile-soil interaction coefficient (ζ follows the power function law) was added.

[0056] Cohesion of composite soil using the action coefficient method:

[0057]

[0058] Internal friction angle of composite soil using the action coefficient method:

[0059]

[0060] ξ=m -0.41 (11)

[0061]

[0062] In the formula: C c For the cohesion of composite soil, C g For the cohesive force of the crushed stone, C sc For the cohesion of the foundation, The internal friction angle of the composite soil. The internal friction angle of the gravel. ζ is the internal friction angle of the foundation, m is the area replacement ratio, and ζ is the pile-soil interaction coefficient.

[0063] In actual engineering, formulas (9) and (12) can be used to calculate the cohesion and internal friction angle of the composite soil, respectively. The slope of the crushed stone pile composite foundation can be regarded as a homogeneous rock and soil body, and the potential sliding surface can be calculated.

[0064] Step 3: Selection of slope excavation displacement monitoring points and installation and layout of monitoring equipment;

[0065] This invention's deformation monitoring primarily measures the horizontal displacement at the slope crest and the horizontal displacement of the slope body, directly reflecting the slope's stability. Within the main slip zone, the number of monitoring points is one every 3 meters of total excavation depth. At the same depth, these points are moved further inwards into the slope, and the same number of displacement monitoring points are continued. The monitoring equipment uses high-performance vibrating wire displacement sensors to monitor the slope's horizontal displacement. Professional advanced drilling equipment is used to place the displacement gauge column inside the hole, and then the sensor is fixed to the column; the length can be adjusted according to the measuring range. The sensors are connected, and a distributed GPRS node wireless data acquisition system is used to collect monitoring data. This system enables multiple interface protocol conversions, automatic wireless data transmission management, and integrated measurement circuitry, which can be expanded to multiple outputs via switches. A high-precision laser rangefinder is installed at the slope crest to monitor the horizontal displacement at the slope crest.

[0066] Step 4: Real-time monitoring and data processing of slope excavation depth and slope displacement;

[0067] According to the construction plan, the depth of each excavation of the composite foundation slope and the resulting displacement response are monitored in real time. Displacement data from each monitoring point is transmitted to the host computer via a wireless data acquisition device. The excavation depth is directly obtained from the construction plan. The monitoring data is then preprocessed and entered into an Excel spreadsheet. The slope excavation depth is denoted as H. i The horizontal displacement caused by excavation is denoted as S. ni , where i represents the excavation stage and n represents the monitoring point number.

[0068] Step 5: Determination of the dynamic load displacement response rate of composite foundation slope excavation;

[0069] In the process of slope excavation for a composite foundation of crushed stone piles, excavation is the main dynamic factor affecting and controlling slope displacement and stability. There is a one-to-one correspondence between excavation depth and slope displacement. Based on principle 2, this patent uses the initial excavation depth H1 of the slope as the initial load, and the corresponding slope top and slope body displacement response S caused by the initial excavation. n1 As the initial displacement response, the initial dynamic load displacement response rate at the top of the slope can be calculated according to equation (3):

[0070]

[0071] The excavation depth of any subsequent excavation step on the slope is taken as the slope dynamic load H of that excavation step. i Horizontal displacement response S caused by slope excavation ni As the displacement response of this excavation step, the dynamic load displacement response rate of any subsequent excavation step of the slope can be calculated according to equation (4):

[0072]

[0073] Principle 2 is as follows:

[0074] Assuming the slope is a homogeneous and isotropic rock and soil mass with a uniformly varying thickness, deformation and instability occur during slope excavation. Soil skeleton blocks within the potential sliding soil mass are selected as the research object. The slope model and the stress conditions of the blocks during excavation are as follows: Figure 3 As shown.

[0075] Depend on Figure 3 It can be seen that the sliding force and the anti-sliding force are components of the slider's gravity. The sliding force is represented by T, and the anti-sliding force is represented by R. The sliding force and the anti-sliding force before and after excavation are expressed by the following formulas:

[0076] Sliding force T1 before excavation:

[0077] T1=G1sinθ=(γH1)sinθ (13)

[0078] Sliding force T2 after excavation:

[0079] T2=G2sinθ=(γH2)sinθ (14)

[0080] Anti-sliding force R1 before excavation:

[0081]

[0082] Anti-sliding force R2 after excavation:

[0083]

[0084] In the formula: c is the cohesion of the sliding surface; Let be the internal friction angle of the sliding surface; l be the width of the bottom surface of the strip; γ be the natural unit weight of the soil; H be the excavation depth; G be the gravity; and θ be the slope inclination angle. Therefore, the incremental slope sliding force ΔP caused by excavation is:

[0085]

[0086] As can be seen from equation (17), for a specific slope, H2 is a constant, while H2-H1 represents the increase in slider height caused by excavation. Only when the slope is excavated downwards will the volume of the potential sliding soil increase, thus increasing the height of the stripped sliding blocks. Therefore, it can be considered that there is a one-to-one correspondence between each excavation depth of the slope and the corresponding increase in residual sliding force.

[0087] Step Six: Determining the evaluation parameters for the dynamic load displacement response ratio of composite foundation slopes;

[0088] Based on the calculation results of step five, the dynamic load displacement response rate λ under any subsequent excavation step of the slope is calculated. ni The initial dynamic load displacement response rate λ of the slope n0 The ratio is defined as the slope dynamic load displacement response ratio for that excavation step. An evaluation model for the slope dynamic load displacement response ratio is established, namely:

[0089]

[0090] In the formula: ΔS n1 ΔS ni The horizontal displacement values ​​are H1 and H2 under the initial excavation step and subsequent excavation steps. i The values ​​represent the dynamic load increases during the initial and subsequent excavation steps. Therefore, the dynamic load displacement response ratio of the slope is used as a stability evaluation parameter to predict and assess its stability.

[0091] Step 7: Determination of the instability criterion for the slope dynamic loading displacement response ratio evaluation parameters;

[0092] By consulting relevant technical specifications such as the "Technical Specification for Design and Construction of Landslide Prevention Engineering" (DZ / T0219-2006) and the "Code for Geotechnical Investigation" (GB50021-2009), and based on the slope safety factor K, and according to Principle 3, the slope dynamic loading displacement response ratio stability criterion based on the safety factor was determined:

[0093] Principle 3 is as follows:

[0094] The elastic modulus E of slope soil and rock is an important parameter characterizing the damage and failure mechanism of slopes. According to the definition of elastic modulus, which is the stress required to produce a unit elastic deformation, it can be expressed by the formula:

[0095]

[0096] Let ξ be the reciprocal of the dynamic load displacement response ratio η, and express it as:

[0097]

[0098] In the formula: σ is stress, ε is deformation, and Δσ i For the stress increment, Δε i Let ξ be the deformation increment, and ξ be the ratio of deformation modulus increments.

[0099] As can be seen from the above formula, when the slope is not damaged, the elastic modulus does not change and its value of ξ is 1; when the slope is completely damaged, the value of ξ is 0; when the slope is partially damaged, the value of ξ varies between 0 and 1.

[0100] According to the basic principles of damage mechanics, the instability process of a slope is actually the damage process of the slip zone soil and rock mass. The damage process and the degree of damage can be expressed by the damage variable D. i express:

[0101]

[0102] However, for slopes with special geological conditions, the overlying rock strata have undergone many years of gestation and evolution, making it impossible to measure the initial elastic modulus of the slope's soil and rock mass. Only the deformation modulus after damage can be obtained. In view of this situation, the damage variable definition formula (Equation (20)) and the deformation modulus E are combined. i The ratio of displacement response to dynamic load increase η i The relationship can be expressed as follows:

[0103]

[0104] In the formula: ξ0 is the ratio of the deformation modulus increment when the slope is in a fully elastic stable state, and its value is 1; ξ i This represents the ratio of the deformation modulus increment under a certain excavation step.

[0105] Analysis of equations (20) and (21) shows that when the slope material is in an elastically stable state, E i =E0, ξ i =ξ0=1,D i =0; When the slope material is in a completely damaged state, E i =0, ξ i =0,D i =1. Therefore, using equations (20) and (21) to describe the damage deformation law of the slope is equivalent, so it is feasible to use the reciprocal ξ of the dynamic load displacement response ratio to analyze and evaluate the stability of the foundation slope at each excavation stage. Furthermore, according to formulas (19) and (21), the relationship between the dynamic load displacement response ratio and the damage variable can be determined:

[0106]

[0107] It can be seen from equation (22) that when D i When η = 0, i =1, at this point the slope is not damaged, the dynamic load displacement response ratio is 1, and the slope is in a stable state; when the slope is completely damaged, i.e. D i When the value approaches 1, the dynamic load displacement response ratio approaches infinity, and the slope is in an unstable state.

[0108] The essence of composite foundation slope failure is that, under external excavation disturbance, the shear force of the complex soil on the slip zone exceeds its shear strength, leading to the failure of the soil structure in the slip zone. Therefore, the damage variable parameter D can be defined from the perspective of soil strength failure.i This represents the probability of failure when the shear stress on the soil surface of a potential slip surface exceeds its shear strength. In slope engineering, the currently accepted criterion for slope stability is the slope stability coefficient, which is used to determine the degree of slope stability based on the relationship between the actual stability coefficient and the safety factor. Zhang Daobing et al. defined the safety factor as the ratio of the ultimate damage to the maximum allowable damage, i.e.:

[0109]

[0110] In the formula: D cr To allow for maximum damage, the limiting damage D im Take 1. During the entire damage and failure process, the damage variable D... i Gradually approaching D cr Therefore, the maximum safety factor can be expressed as:

[0111]

[0112] The above formula shows that there is a one-to-one correspondence between the dynamic load displacement response ratio of the slope and the slope safety factor, that is, the dynamic load displacement response ratio parameter can be used to quantitatively evaluate the slope stability.

[0113]

[0114] When the displacement response ratio parameter η is increased by dynamic loading ni Less than or equal to η cr When the slope is in a stable state, it indicates that the slope is in a stable state; when the dynamic load displacement response ratio parameter η ni Greater than η cr This indicates that the slope is in an unstable state and there is a possibility of landslide.

[0115] Step 8: Determine and evaluate the stability of composite foundation slopes by comparing dynamic load displacement response.

[0116] Using the excavation depth of each stage of the composite foundation slope as the dynamic load increase, and the displacement or displacement rate caused by the excavation depth as the corresponding response quantity, the dynamic load displacement response ratio parameter and evaluation model of the slope are determined, and these parameters are used as evaluation parameters for slope stability prediction and forecasting during the excavation process of the composite foundation slope. Simultaneously, based on the fundamental principles of damage mechanics, a quantitative relationship between the dynamic load displacement response ratio and the foundation slope stability coefficient is established through the damage variable parameter D. Based on this quantitative relationship, the stability early warning criterion for the dynamic load displacement response ratio of the foundation slope is determined.

[0117] To illustrate the invention in more detail, the following section uses a foundation slope in Qingdao as an example to measure and evaluate its excavation stability. The designed excavation depth of the foundation is 10m, divided into 8 excavation steps, with the initial excavation reaching 1.5m, and the excavation proceeding in layers. The initial design of the foundation used a crushed stone pile support structure, with a total length of 17m, a diameter of 1000mm, and a spacing of 1.4m.

[0118] Step 1: Exploration and determination of shear strength parameters of foundation slope

[0119] The soil cohesion (c) of the slope layer of the gravel pile composite foundation slope was determined to be 7.7 kPa using in-situ soil and rock tests or laboratory geotechnical tests, and the internal friction angle was determined to be... The internal friction angle is 5.8°; and the cohesion c of the crushed stone pile is determined to be 0 kPa, and the internal friction angle is determined to be 5.8°. The angle is 36°; the replacement rate is the ratio of the unit area.

[0120] Step 2: Determining the most dangerous potential slip surface of the gravel pile composite foundation slope

[0121] Based on principle 1, formulas (1) and (2), and the measured shear strength parameters of the soil layer and the crushed stone piles on the slope of the composite foundation, the cohesion and internal friction angle of the composite soil were calculated under the condition of a replacement rate of 40%. The slope of the composite foundation was regarded as homogeneous rock and soil. The calculated cohesion c of the composite soil was 5.11 kPa, and the internal friction angle was... The slope is 29.8°, and the most dangerous slip surface is calculated using the classical circular arc method. The characteristics of the slope, such as its dimensions and distribution range, are analyzed to determine the main slip zone. Figure 4 .

[0122]

[0123]

[0124] Step 3: Selection of slope excavation displacement monitoring points and installation of monitoring equipment

[0125] To directly reflect the stability of the slope, it is necessary to monitor the horizontal displacement at the slope crest and the horizontal displacement of the slope body. For an excavation depth of 10m, three monitoring points can be set up. Then, moving the monitoring points 3m inwards towards the slope, the same number of displacement monitoring points can be set up again. Figure 2As shown, a high-performance vibrating wire displacement sensor is used to monitor the horizontal displacement of the slope. Specialized advanced drilling equipment is used to install the displacement gauge column inside the hole, and then the sensor is fixed to the column; the length can be adjusted according to the measuring range. The sensors are connected, and a distributed GPRS node wireless data acquisition system is used to collect monitoring data. This system enables multiple interface protocol conversions, automatic wireless data transmission management, and integrates internal measurement circuitry, expanding to multiple outputs via switches. A high-precision laser rangefinder is installed at the slope crest to monitor the horizontal displacement at the crest.

[0126] Step 4: Real-time monitoring and data processing of slope excavation depth and slope displacement

[0127] According to the construction plan, the depth of each excavation of the composite foundation slope and the resulting displacement response are monitored in real time. Displacement data from each monitoring point is transmitted to the host computer via a wireless data acquisition device. The excavation depth is directly obtained from the construction plan. The monitoring data is then preprocessed and entered into an Excel spreadsheet. The slope excavation depth is denoted as H. i The horizontal displacement of the slope is denoted as S. ni Where i represents the excavation stage and n represents the monitoring point number, as shown in Table 1.

[0128] Table 1. Monitoring data of slope excavation

[0129]

[0130] Step 5: Determination of the dynamic load displacement response rate of composite foundation slope excavation

[0131] During the excavation of a gravel pile composite foundation slope, excavation is the main dynamic factor affecting and controlling slope displacement and stability. There is a one-to-one correspondence between excavation depth and slope displacement. Based on principle 2, the initial excavation depth of the slope is taken as the initial load H1, and the horizontal displacement response S caused by the initial excavation is... 11 S 21 As the initial displacement response, the initial dynamic load displacement response rate at the top of the slope can be calculated according to equation (3):

[0132]

[0133] The excavation depth of any subsequent excavation step on the slope is taken as the slope dynamic load H of that excavation step. i Horizontal displacement response S caused by slope excavation ni As the displacement response of this excavation step, the dynamic load displacement response rate of any subsequent excavation step of the slope can be calculated according to equation (4), and the calculation results are shown in Table 2.

[0134]

[0135] Table 2 Displacement Response Rate under Dynamic Loading

[0136]

[0137]

[0138] Step Six: Determination of the Evaluation Model for Dynamic Loading Displacement Response Ratio of Composite Foundation Slope

[0139] Based on the calculation results of step three, the dynamic load displacement response rate λ under any subsequent excavation step of the slope is calculated. i The initial dynamic load displacement response rate λ of the slope n0 The ratio is defined as the slope dynamic load displacement response ratio for that excavation step. An evaluation model for the slope dynamic load displacement response ratio is established, namely:

[0140]

[0141] In the formula: ΔS n1 ΔS ni These are the displacement values ​​for the initial excavation step and subsequent excavation steps; H1, H i The dynamic load values ​​are for the initial excavation step and subsequent excavation steps.

[0142] Therefore, the dynamic load displacement response ratio of the slope is used as the stability evaluation parameter of the slope to predict and evaluate its stability. The calculation results are shown in Table 3.

[0143] Table 3 Displacement Response Ratio under Dynamic Loading

[0144]

[0145] Step 7: Determination of Instability Criteria for Slope Dynamic Loading Displacement Response Ratio Evaluation Parameters

[0146] By consulting relevant technical specifications such as the "Technical Specification for Design and Construction of Landslide Prevention Engineering" (DZ / T0219-2006) and the "Code for Geotechnical Investigation" (GB50021-2009), the maximum safety factor K of the slope was determined. cr A value of 1.3 is used to satisfy the stable state with sufficient safety margin. According to principle 3, K... cr Substituting into formula (25), the slope dynamic loading displacement response ratio stability criterion based on the maximum safety factor is determined, and η can be obtained. cr It is 4.33.

[0147]

[0148] When the displacement response ratio parameter η is increased by dynamic loading ni Less than or equal to η cr When the slope is in a stable state, it indicates that the slope is in a stable state; when the dynamic load displacement response ratio parameter ηni Greater than η cr This indicates that the slope is in an unstable state and there is a possibility of landslide.

[0149] Step 8: Determine and evaluate the stability of composite foundation slopes by comparing dynamic load displacement response.

[0150] The dynamic load displacement response ratio of the slope is used as a dynamic evaluation parameter for monitoring and early warning of slope stability. This parameter is then used to monitor and evaluate slope stability, based on the dynamic load displacement response ratio η under any excavation step. ni With the instability criterion value η cr Comparing the two, it is clear that the dynamic load displacement response under any excavation step is better than η. ni Both are more than the instability criterion value η cr A small value indicates that the slope is in a stable state.

[0151] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining an excavation dangerous slip surface of a stone column composite foundation, characterized by, Comprising the following steps: Step one, using geotechnical in-situ test or indoor geotechnological test to determine the cohesion C of the composite soil of the slope body of the gravel pile composite foundation c , the internal friction angle of the composite soil and the cohesion C of the gravel g , the internal friction angle of the gravel Step two, formula (1), (2), and the measured stone pile composite foundation slope soil and stone pile shear strength parameters, the cohesion and internal friction angle of composite soil are calculated, the stone pile composite foundation slope is regarded as a homogeneous rock-soil body, and the most dangerous sliding surface is calculated by the classical circular arc method, wherein: C c C is the cohesion of the composite soil, g C is the cohesion of the crushed stone, sc C is the cohesion of the foundation, m is the area replacement ratio. m is the area replacement ratio. m is the area replacement ratio.

2. A method for determining the stability of a dangerous slip surface of a stone column composite foundation during excavation, wherein the method of claim 1 is used to determine the slip surface, and the deformation monitoring includes measuring the horizontal displacement of the slope top and the horizontal displacement of the slope body to reflect the stability state of the slope; characterized in that, Comprising the following steps: Step three: selection of slope excavation displacement monitoring points and installation and arrangement of monitoring equipment; Step four: real-time monitoring and data processing of slope excavation depth and slope displacement; Step five: determination of dynamic load increment displacement response rate of composite foundation slope excavation; Step six: determination of dynamic load increment displacement response ratio evaluation parameter of composite foundation slope; Step seven: determination of dynamic load increment displacement response ratio evaluation parameter instability criterion of slope; Step eight: determination and evaluation of the stability of the composite foundation slope by using the dynamic load increment displacement response ratio.

3. The method according to claim 2, wherein the method is characterized by, In step three, high-performance vibrating string displacement sensors are used to monitor the horizontal displacement of the slope. The number of monitoring points is one per L meters of total excavation depth. At the same depth, the same number of displacement monitoring points are arranged inside the slope. Distributed GPRS node wireless data acquisition system is used for monitoring data acquisition.

4. The method according to claim 2, wherein the method is characterized by, The depth of each excavation of the composite foundation slope and the horizontal displacement response caused thereby are monitored in real time; the horizontal displacement is transmitted by a radio collection device of a monitoring device to a host computer, the excavation depth is directly obtained from a construction scheme, and then the monitoring data is preprocessed and entered into an Excel table; the excavation depth of the slope is denoted as H i , and the horizontal displacement caused by excavation is denoted as S ni , wherein i is an excavation stage, and n is a monitoring point label.

5. The method according to claim 2, wherein the method is characterized by, In the fifth step, in the process of excavation of the stone pile composite foundation slope, the excavation is the main dynamic factor affecting and controlling the displacement and stability of the slope, and the excavation depth and the slope displacement have a one-to-one correspondence. The initial excavation depth H1 of the slope is taken as the initial load increment, and the horizontal displacement S n1 As the initial displacement response, the initial dynamic load increment displacement response rate of the slope top can be calculated according to formula (3): The excavation depth of the slope after any subsequent excavation step is taken as the dynamic load increment H of the slope for that excavation step i The horizontal displacement S caused by the slope excavation ni According to equation (4), the dynamic load increment displacement response rate of the slope after any subsequent excavation step can be calculated as the displacement response quantity for that excavation step 6. The method according to claim 5, wherein the method is characterized by, In step six, the dynamic load displacement response rate λ under any subsequent excavation step of the slope is calculated. ni The initial dynamic load displacement response rate λ of the slope n0 The ratio is defined as the slope dynamic load displacement response ratio for that excavation step. An evaluation model for the slope dynamic load displacement response ratio is established, namely: wherein: ΔS n1 , ΔS ni is the horizontal displacement value under the initial excavation step and the subsequent excavation step; H i is the dynamic load value under the initial excavation step and the subsequent excavation step, whereby the slope dynamic load displacement response ratio is taken as the stability evaluation parameter of the slope, and the stability of the slope is predicted and evaluated.

7. The method according to claim 5, wherein the method is characterized by, The safety factor K is defined as the ratio of the ultimate damage to the allowable maximum damage, that is: where D cr D is the ultimate damage im D is the ultimate damage i D is the ultimate damage cr D is the ultimate damage cr D is the ultimate damage The above formula shows that there is a one-to-one correspondence between the dynamic load increment displacement response ratio of the slope and the safety factor of the slope, that is, the dynamic load increment displacement response ratio parameter can be used to quantitatively evaluate the stability of the slope; When the dynamic load increment displacement response ratio parameter η ni is less than or equal to η cr , it indicates that the slope is in a stable state; when the dynamic load increment displacement response ratio parameter η ni is greater than η cr , it indicates that the slope is in an unstable state and has the possibility of landslide.

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