Foundation pit support design and deformation evaluation method considering obstruction influence of existing underground structure

Abstract

The invention discloses a foundation pit supporting design and deformation evaluation method considering the existing underground structure obstruction influence. The method comprises the steps that an out-pit ground surface settlement curve function is constructed at a plurality of target areas; defining an out-pit surface settlement curve form of each target area; all the out-pit ground surface settlement curves are integrated, the position with the maximum out-pit ground surface settlement is predicted through multiple preset working condition models, and the distance between the position with the maximum out-pit ground surface settlement and the edge of the foundation pit is calculated; determining a settlement influence range represented in the out-pit ground surface settlement curve under each working condition model; according to a double-row spring model, solving a side displacement area value of the enclosure structure; and establishing a linear relation model between the settlement area value of the ground surface outside the pit and the lateral displacement area value of the enclosure structure so as to predict the settlement of the ground surface outside the pit. According to the method, the accuracy of predicting the deformation of the ground surface outside the pit is improved, the deformation condition of the ground surface outside the pit can be accurately predicted, and technical support is provided for reasonable construction design.

Description

Technical Field

[0001] The present invention specifically relates to the technical field of foundation pit settlement prediction, and in particular is a foundation pit support design and deformation evaluation method that takes into account the barrier effect of existing underground structures. Background Art

[0002] With the rapid development of cities, the development of underground space has received more and more attention. The construction of high-rise buildings, super high-rise buildings and subways will involve deep foundation pit projects. Due to the high technical requirements and strong comprehensiveness of deep foundation pit projects, serious engineering accidents are very likely to occur in some deep foundation pit projects. During the excavation of deep foundation pits, if the groundwater level drops too much or the retaining structure of the foundation pit is greatly deformed, the ground around the foundation pit may have a large settlement effect. If there is a large uneven change in the settlement near the foundation pit excavation area, it will also cause major problems such as foundation tilting, wall cracking, and serious damage to roads and underground pipelines. With the increase in excavation depth, it is inevitable to involve foundation pit dewatering, especially in areas with high groundwater levels. When excavating foundation pits, it is bound to involve the problem of dewatering within the excavation range to meet the requirements of dry operations on the foundation pit excavation surface. The decrease in groundwater level will cause changes in the seepage field and stress field in the excavation area, resulting in a decrease in pore water pressure and an increase in effective stress in the soil, which will eventually lead to consolidation and settlement of the soil, causing the strata around the foundation pit to settle, threatening the safety of the structures around the foundation pit. Excavating foundation pits in densely populated urban areas will inevitably affect the foundations of the buildings, causing uneven settlement and affecting the safety of the buildings, which makes the control of strata settlement more stringent. In areas with abundant groundwater, precipitation seepage will cause varying degrees of damage to surrounding underground pipelines and buildings, and may even cause sand flow, pipe bursts, instability at the bottom of the pit, and collapse of the pit wall, posing a great challenge to the stability of the foundation pit.

[0003] When a foundation pit project in a city is adjacent to an existing subway station, precipitation before excavation of the foundation pit will have a significant impact on the surrounding environment due to the barrier effect of the subway station. At present, the research focus in the foundation pit field is mainly on the excavation stage, and the precipitation stage before excavation has not received enough attention. At the same time, the current foundation pit design manual does not propose a prediction technology for the surface settlement outside the pit caused by precipitation before excavation under the barrier effect of the existing subway station. Summary of the invention

[0004] The purpose of the present invention is to provide a foundation pit support design and deformation evaluation method taking into account the barrier effect of existing underground structures, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A foundation pit support design and deformation evaluation method considering the barrier effect of existing underground structures includes the following steps:

[0007] Based on the deformation law of the surface settlement curve outside the pit, the surface settlement curve function outside the pit is constructed at multiple target areas;

[0008] Using a normal distribution function to define the form of the surface settlement curve outside the pit at each target area;

[0009] Comprehensively analyzing all the surface settlement curves outside the pit, using the preset multiple working condition models to predict the location of the maximum surface settlement outside the pit, and calculating the distance between the location of the maximum surface settlement outside the pit and the edge of the foundation pit;

[0010] Determine the settlement impact range represented in the surface settlement curve outside the pit under each operating model;

[0011] Based on the double-row spring model, the interaction between soil bodies is simulated, and the lateral displacement area of ​​the retaining structure is calculated according to the change in soil pressure inside and outside the foundation pit represented by the change in spring stiffness.

[0012] A linear relationship model between the surface settlement area outside the pit and the lateral displacement area of ​​the retaining structure is established to predict the surface settlement outside the pit.

[0013] As a further solution of the present invention: a prediction formula model based on the normal distribution function is obtained according to the maximum settlement value of the surface outside the pit and the normal distribution function to predict the settlement area of ​​the surface outside the pit.

[0014] As a further solution of the present invention: the multiple target areas include the front side of the subway station, the subway station and the back side of the subway station, and the surface settlement curve function outside the pit includes the curve segment in front of the subway station, the curve segment at the subway station and the curve segment behind the subway station.

[0015] As a further solution of the present invention: the surface settlement curve function outside the pit at each section in the target area is:

[0016]

[0017] In the formula, δ max Indicates the maximum value of surface settlement; x m Indicates the maximum position of surface settlement; x indicates the horizontal distance from the foundation pit; r indicates the impact radius, r = x0-x m ; x0 represents the settlement influence range.

[0018] As a further solution of the present invention, a relationship between the maximum settlement values ​​of the three target areas, namely, the front side of the subway station, the subway station and the rear side of the subway station, is established:

[0019]

[0020] Where D is the distance between the foundation pit and the subway station; δmax(1), δmax(2), and δmax(3) are the maximum settlement values ​​of the surface settlement curve outside the pit in front of the subway station, at the subway station, and behind the subway station, respectively.

[0021] As a further solution of the present invention: using a normal distribution function to define the form of the surface settlement curve outside the pit at each target area: obtaining historical surface settlement data outside the pit at different locations;

[0022] The parameters of the normal distribution are estimated based on the acquired data and the normal distribution function is constructed to form the surface settlement curve outside the pit.

[0023] As a further solution of the present invention: determining the settlement influence range under each working condition model specifically includes:

[0024] Preset and divide the main and secondary areas of settlement, and determine the critical positions of the main and secondary areas;

[0025] According to the position of the critical point, define the relationship between the settlement amount at the critical point and the maximum settlement value of the surface outside the pit and obtain the settlement value at the position of the critical point according to the corresponding relationship;

[0026] Taking the settlement value at the critical position as the entry point, combined with the settlement distribution under each working condition model, all positions in the settlement distribution where the settlement exceeds a preset threshold are identified to obtain the settlement influence range.

[0027] As a further solution of the present invention: calculating the distance between the position of the maximum surface settlement outside the pit and the edge of the foundation pit specifically includes:

[0028] According to the distance between the foundation pit and the subway station, calculate the distance between the maximum settlement position in front of the station and the edge of the foundation pit, and the distance between the maximum settlement position in the rear of the station and the edge of the foundation pit;

[0029] The formula for the distance from the maximum position of the surface settlement outside the pit to the edge of the foundation pit under different spacings is:

[0030]

[0031] Where D represents the distance between the foundation pit and the subway station, Xm1 represents the distance between the maximum settlement position in front of the station and the edge of the foundation pit, Xm2 represents the distance between the maximum settlement position at the station and the edge of the foundation pit, and Xm3 represents the distance between the maximum settlement position at the rear of the station and the edge of the foundation pit.

[0032] As a further solution of the present invention: establishing a linear relationship model between the surface settlement area value outside the pit and the lateral displacement area value of the enclosure structure specifically includes: analyzing the surface settlement area value outside the pit and the lateral displacement area value of the enclosure structure in each working condition model; according to the surface settlement area value outside the pit and the lateral displacement area value of the enclosure structure obtained in different working condition models, establishing a unified linear relationship between the two: A w =αA sν Among them, A sν A is the surface settlement area outside the pit; w is the lateral displacement area value of the enclosure structure; α is the proportional relationship.

[0033] As a further solution of the present invention: obtaining a prediction formula model based on the normal distribution function according to the maximum value of the surface settlement outside the pit and the normal distribution function specifically includes:

[0034] Substitute the maximum value of the surface settlement outside the pit into the assumed normal distribution function to solve the prediction formula for the surface settlement area outside the pit:

[0035]

[0036] X 车站 Where erf is the error function, Indicates the horizontal distance between the station and the foundation pit;

[0037] Based on the relationship between the surface settlement area outside the pit and the area of ​​the enclosure structure A w =αA sν The relationship between the maximum settlement values ​​of the three target areas, namely, the front side of the subway station, the subway station and the rear side of the subway station, is calculated to obtain the maximum surface settlement δmax(1) outside the pit in front of the subway station and the lateral displacement area of ​​the enclosure A. w relationship;

[0038] The prediction formula for the maximum value of the surface settlement outside the pit in front of the subway station, δmax(1), is obtained as follows:

[0039]

[0040] Based on the prediction formula of the maximum value of the surface settlement outside the pit δmax(1) in front of the subway station and the relationship between the maximum settlement values ​​of the three target areas in front of the subway station, at the subway station and behind the subway station, the prediction formula of the maximum value of the surface settlement outside the pit δmax(2) at the subway station and the prediction formula of the maximum value of the surface settlement outside the pit δmax(3) at the back of the subway station are respectively obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of foundation pit support design and deformation evaluation method considering the barrier effect of existing underground structures.

[0042] Figure 2 The present invention is a flow chart for defining the form of the surface settlement curve outside the pit at the target area by using the normal distribution function. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In the embodiments of the present invention, the surface settlement outside the pit refers to the phenomenon that the ground around the foundation pit sinks due to the unloading of the soil, the change of the groundwater level, the lateral deformation of the surrounding structure and other reasons during the foundation pit excavation construction.

[0045] The surface settlement curve outside the pit is a graphical representation of the change in surface settlement around the foundation pit with position during the construction of the foundation pit. This curve usually uses the horizontal distance (such as the distance from the edge of the foundation pit) as the horizontal coordinate and the settlement as the vertical coordinate.

[0046] See also Figure 1-Figure 2 The present invention provides a foundation pit support design and deformation evaluation method considering the barrier effect of existing underground structures, that is, a method for predicting surface settlement outside the pit caused by precipitation before excavation under the barrier effect of existing subway stations, wherein the foundation pit support design can be understood as the calculation of the lateral displacement of the enclosure structure, and the deformation evaluation can be understood as the prediction of surface settlement outside the pit, including the following steps:

[0047] Step S101: constructing a surface settlement curve function outside the pit at multiple target areas based on the deformation law of the surface settlement curve outside the pit.

[0048] It should be noted that the deformation law of the surface settlement curve outside the pit is usually affected by many factors, including the excavation depth of the foundation pit, the design of the retaining structure, geological conditions, etc. Take the above factors as an example to further explain:

[0049] The maximum surface settlement outside the pit is usually between 0.04%H and 0.24%H, with an average value of about 0.10%H (H is the excavation depth of the foundation pit). This shows that the surface settlement value is proportional to the excavation depth of the foundation pit.

[0050] In most cases, the surface settlement outside the pit is distributed in a groove shape, and the affected area can reach 3.5H. The maximum surface settlement usually occurs outside the retaining wall, mainly concentrated in the range of 0.13H to 0.6H from the retaining wall, with an average value of about 0.4H.

[0051] The ratio of the maximum surface settlement outside the pit to the maximum lateral deformation of the retaining wall ranges from 0.25 to 1.62, with an average value of about 0.58. This shows that there is a certain correlation between the surface settlement and the lateral deformation of the retaining structure, but the maximum surface settlement is generally smaller than the maximum lateral deformation of the retaining structure.

[0052] In addition, the deformation law of the surface settlement curve outside the pit also includes factors such as time, which will not be elaborated here.

[0053] In one embodiment, the plurality of target areas include the front side of a subway station, the area at the subway station, and the back side of the subway station.

[0054] According to the deformation law of the surface settlement curve outside the pit, the surface settlement curve function outside the pit is constructed in three places: in front of the subway station, at the subway station and behind the subway station. It is used to mathematically express the law of settlement changing with position. That is, mathematical expressions are used to describe and simulate the spatial distribution characteristics of surface settlement caused by foundation pit construction.

[0055] In this way, by constructing the surface settlement curve function outside the pit to predict the surface settlement that may occur at different locations during the foundation pit construction, it can help engineers evaluate the potential impact of construction activities on surrounding buildings, infrastructure and the environment, and take preventive measures to reduce damage.

[0056] In this step of the present invention, the surface settlement curve function outside the pit is:

[0057]

[0058] In the formula, δ max Indicates the maximum value of surface settlement; x m Indicates the maximum position of surface settlement; x indicates the horizontal distance from the foundation pit; r indicates the impact radius, r = x0-x m ; x0 represents the settlement influence range.

[0059] Establish the relationship between the maximum settlement values ​​of the three target areas: the front side of the subway station, the subway station, and the back side of the subway station:

[0060]

[0061] Where D is the distance between the foundation pit and the subway station; δmax(1), δmax(2), and δmax(3) are the maximum settlement values ​​of the surface settlement curve outside the pit in front of the subway station, at the subway station, and behind the subway station, respectively.

[0062] Through these relationships, the settlement of the first section can be used to predict the settlement of the second and third sections under specific precipitation conditions and correlate them with the settlement of the first section.

[0063] Step S102: using a normal distribution function to define the surface settlement curves outside the pit at a plurality of target areas.

[0064] The graph of the normal distribution function is a symmetrical bell-shaped curve, which is used to approximate the distribution of surface settlement with location. The normal distribution function is used to simulate the probability distribution of surface settlement in different regions. The settlement curve of each region can be defined by the normal distribution function, which has a specific mean (μ) and standard deviation (σ), where the mean represents the location with the largest settlement.

[0065] The normal distribution function not only defines the probability density of settlement, but can also be used to calculate the probability of a specific settlement. Using the normal distribution function, it is possible to predict the settlement that may occur at different locations and the probability of these settlements. This is very important for assessing the impact of settlement on the surrounding environment and risk management.

[0066] Specifically, the form of the surface settlement curve outside the pit at the target area is defined by using a normal distribution function, including:

[0067] Step S102-1, obtaining surface settlement data outside the pit at different locations during previous foundation pit construction.

[0068] Step S102-2: Estimate the parameters of the normal distribution, namely the mean (μ) and the standard deviation (σ), based on the collected data. The mean can represent the location with the largest sedimentation, while the standard deviation can reflect the degree of variation of the sedimentation.

[0069] Step S102-3: Use the estimated parameters to construct a normal distribution function to fit the actual observed settlement data to form a surface settlement curve outside the pit.

[0070] Through the normally distributed surface settlement curve outside the pit, the spatial distribution characteristics of surface settlement can be analyzed, the possible settlement amount at different locations can be predicted, and the impact of settlement on the surrounding environment can be evaluated. The method of using the normal distribution function to define the settlement curve can provide theoretical support for foundation pit engineering design and construction, helping engineers to better understand and control the surface settlement phenomenon during the construction process.

[0071] It should be noted that when applying it, it may be necessary to combine it with other statistical methods or experience judgment for adjustment and optimization.

[0072] Step S103, synthesizing all the surface settlement curves outside the pit, using a preset plurality of working condition models to predict the location of the maximum surface settlement outside the pit, and calculating the distance between the location of the maximum surface settlement outside the pit and the edge of the foundation pit.

[0073] According to different construction conditions (such as precipitation scheme, excavation depth, support structure, etc.), multiple working condition models are established to simulate different situations that may be encountered during the construction process. Multiple working condition models are used to predict and analyze each surface settlement curve outside the pit, and the position of the maximum surface settlement outside the pit of each curve is obtained. That is, in each working condition model, the position with the largest surface settlement is found by analyzing the normal distribution curve (that is, the position where the mean μ in the normal distribution function is located).

[0074] It should be noted that the position of the maximum value of the surface settlement outside the pit under each set of working conditions will be different. Through analysis of multiple groups, a statistical method is used to obtain the accurate position of the maximum value of the surface settlement outside the pit in multiple curves and multiple working conditions.

[0075] Calculate the distance between the maximum surface settlement position outside the pit and the edge of the foundation pit: According to the distance between the foundation pit and the subway station, calculate the distance between the maximum settlement position in front of the station and the edge of the foundation pit, and the distance between the maximum settlement position in the back of the station and the edge of the foundation pit;

[0076] The formula for the distance from the maximum position of the surface settlement outside the pit to the edge of the foundation pit under different spacings is:

[0077]

[0078] Where D represents the distance between the foundation pit and the subway station, Xm1 represents the distance between the maximum settlement position in front of the station and the edge of the foundation pit, Xm2 represents the distance between the maximum settlement position at the station and the edge of the foundation pit, and Xm3 represents the distance between the maximum settlement position at the rear of the station and the edge of the foundation pit.

[0079] It should be noted that the surface settlement outside the pit (mainly the front and rear sides of the subway station in the subway project embodiment) is closely related to the horizontal displacement of the foundation pit enclosure structure. In the subway station embodiment, based on the statistical analysis of multiple groups of working conditions, the distance from the maximum surface settlement position to the foundation pit edge is found to be different for different subway station depths H and foundation pit widths B. m Basically the same, mainly related to D.

[0080] Step S104: determine the settlement influence range represented by the surface settlement curve outside the pit under each working condition model.

[0081] The implementation process of determining the settlement influence range under each working condition model is:

[0082] Preset and divide the main and secondary areas of settlement, and determine the critical positions of the main and secondary areas;

[0083] According to the position of the critical point, the relationship between the settlement at the critical point and the maximum surface settlement outside the pit is defined, and the settlement value at the critical point is obtained according to the corresponding relationship; in one embodiment, it is assumed that the critical point affecting the primary and secondary areas is at a horizontal position twice the excavation depth of the foundation pit, and its size is determined as half of the maximum surface settlement according to the settlement distribution law of the obtained model.

[0084] Taking the settlement value at the critical position as the entry point, combined with the settlement distribution under each working condition model, all locations in the settlement distribution where the settlement exceeds the preset threshold are identified to obtain the settlement impact range. This threshold is determined based on safety standards, engineering requirements or environmental sensitivity.

[0085] Step S105, the lateral displacement area value of the enclosure structure is calculated based on the double-row spring model. That is, based on the double-row spring model, the interaction between soil bodies is simulated, and the lateral displacement area value of the enclosure structure is calculated according to the change in soil pressure inside and outside the foundation pit represented by the change in spring stiffness.

[0086] The nonlinear double-row spring model is used to solve the problem of lateral displacement of foundation pit enclosures. The model is based on the Winkler foundation beam theory and simulates the interaction between soil bodies by adjusting the spring stiffness, in which the base bed coefficient changes with the lateral displacement and depth of the enclosure. During the dewatering process before excavation, the change in soil pressure inside and outside the foundation pit is replaced by springs. It is assumed that the enclosure structure completely blocks the hydraulic connection inside and outside the foundation pit, and the pore water pressure is reduced and converted into effective stress of the soil, resulting in a pressure difference on both sides of the enclosure, which in turn causes the lateral displacement of the enclosure.

[0087] The nonlinear double-row spring model is: ΔP = K h δ(z);

[0088] Among them, ΔP represents the pressure difference on both sides of the enclosure, K h It represents the horizontal base coefficient of foundation soil, and δ(z) represents the lateral displacement value at the depth z of any enclosure structure calculation point.

[0089] It should be noted that the lateral displacement of the enclosure structure is predicted according to the nonlinear double-row spring model, and the lateral displacement of the enclosure structure is integrated along the depth direction according to the prediction of the lateral displacement by the nonlinear double-row spring model to obtain the area value of the lateral displacement area of ​​the enclosure.

[0090] In the above model, the horizontal base coefficient of foundation soil includes the calculation formulas of the horizontal base coefficient of foundation soil in active zone and passive zone.

[0091] The calculation formula of the horizontal base coefficient of active zone foundation soil is:

[0092]

[0093] The calculation formula for the horizontal base coefficient of passive zone foundation soil is:

[0094] When z≤H d hour:

[0095]

[0096] When z>H d hour:

[0097]

[0098] γ w represents the gravity of water, λ represents the reduction factor, K0 represents the static side pressure coefficient, H d Indicates the precipitation depth, Where ν represents Poisson’s ratio; is the soil parameter; It is the angle between the boundary line between the disturbed area and the non-disturbed area of ​​the soil and the horizontal direction; H is the depth of the enclosure structure; z represents the depth of the calculation point of the enclosure structure.

[0099] Step S106: Establish a linear relationship model between the surface settlement area value outside the pit and the lateral displacement area value of the enclosure structure to predict the settlement of the surface outside the pit.

[0100] Specifically, the values ​​of the surface settlement area outside the pit and the lateral displacement area of ​​the enclosure structure in each working condition model are analyzed;

[0101] According to the surface settlement area outside the pit and the lateral displacement area of ​​the enclosure structure obtained in different working condition models, a unified linear relationship between the two is established: A w =αA sν ;

[0102] Among them, A sν A is the surface settlement area outside the pit; w is the lateral displacement area value of the enclosure structure; α is the proportional relationship.

[0103] It should be noted that the settlement of the surface outside the pit is mainly caused by the lateral displacement of the enclosure structure. In theory, the lateral displacement area of ​​the enclosure should be equal to the surface settlement area. However, due to the influence of other factors, such as the geological conditions of the soil layer and the stiffness of the enclosure structure, the relationship between the two can be expressed by a linear function. The lateral displacement area of ​​the enclosure and the surface settlement area are solved by integration, that is, the area of ​​infinitesimal rectangles is calculated and accumulated. In order to determine the coefficient of the linear function between the two and provide relevant references, the lateral displacement area of ​​the enclosure and the surface settlement area of ​​all working conditions are uniformly analyzed to obtain the surface settlement area A outside the pit. sν The lateral displacement area A of the enclosure structure w The proportional relationship between them, that is, A w =αA sν , and the surface settlement outside the pit is predicted by using the linear relationship between the two.

[0104] In this way, a linear relationship model between the surface settlement area value outside the pit and the lateral displacement area value of the enclosure structure is established, and this linear relationship is used to predict the surface settlement.

[0105] Step S107, obtaining a prediction formula model based on the normal distribution function according to the maximum value of the surface settlement outside the pit and the normal distribution function, so as to predict the settlement of the surface outside the pit.

[0106] Substitute the maximum value of the surface settlement outside the pit into the assumed normal distribution function to solve the prediction formula for the surface settlement area outside the pit:

[0107]

[0108] X 车站 Where erf is the error function, Indicates the horizontal distance between the station and the foundation pit;

[0109] Based on the relationship between the surface settlement area outside the pit and the area of ​​the enclosure structure A w =αA sν The relationship between the maximum settlement values ​​of the three target areas, namely, the front side of the subway station, the subway station and the rear side of the subway station, is calculated to obtain the maximum surface settlement δmax(1) outside the pit in front of the subway station and the lateral displacement area of ​​the enclosure A. w relationship;

[0110] The prediction formula for the maximum value of the surface settlement outside the pit in front of the subway station, δmax(1), is obtained as follows:

[0111]

[0112] Based on the prediction formula of the maximum value of the surface settlement outside the pit δmax(1) in front of the subway station and the relationship between the maximum settlement values ​​of the three target areas in front of the subway station, at the subway station and behind the subway station, the prediction formula of the maximum value of the surface settlement outside the pit δmax(2) at the subway station and the prediction formula of the maximum value of the surface settlement outside the pit δmax(3) at the back of the subway station are respectively obtained.

[0113] For example, the scope of the impact of surface settlement outside the pit in front of the station is determined as follows:

[0114] First, it is assumed that the critical point of influence of the primary and secondary areas is at a horizontal position twice the depth of the foundation pit excavation, and its size is determined as half of the maximum surface settlement according to the settlement distribution law of the obtained model. Substitute the coordinates (2Hi, 0.5δmax) into the following formula (1) to obtain formula (2). Then, according to the relationship between the critical points of influence of the primary and secondary areas in the surface settlement curve, formula (3) is obtained. Then, formula (2) and (3) are combined to obtain (4). According to r = x0-x m, combining (3) and (4) to obtain formula (5), finally the foundation pit excavation depth Hi and the obtained x m Substituting into equation (5), the impact range x0 of precipitation in front of the subway station before excavation can be calculated.

[0115]

[0116] According to the geometric relationship of special positions in the above surface settlement curve, we can get:

[0117] x m +x p =2H i (3)

[0118] Among them, x p It is the horizontal distance between the maximum surface settlement and the critical point of influence of the primary and secondary areas; Hi is the excavation depth of the foundation pit.

[0119] Combining equations (2) and (3), we can get:

[0120] x p =0.47r (4)

[0121] Then according to r = x0-x m , and combining equations (3) and (4) we can get:

[0122] 0.5x m +0.47x0=2H i (5)

[0123] Finally, according to the relationship between the maximum settlement values ​​of the three target areas in front of the subway station, at the subway station and at the back of the subway station, the influence range of the surface settlement outside the pit at the subway station and at the back of the subway station can be determined.

[0124] This application determines several related parameters that need to be sought through an assumed function; then determines the relationship between the various parameters through special position coordinates and the established numerical model; then determines the maximum value of the surface settlement outside the pit through the relationship between the area of ​​the retaining structure and the surface settlement area outside the pit in the stratum loss method; finally, by substituting the obtained maximum surface settlement into the assumed function, the surface settlement values ​​outside the pit at different distances from the retaining structure can be predicted.

[0125] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0126] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole.

[0127] The solutions may also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims

1. A foundation pit support design and deformation evaluation method considering the barrier effect of existing underground structures, characterized in that: The following steps are involved: Based on the deformation law of the surface settlement curve outside the pit, the surface settlement curve function outside the pit is constructed at multiple target areas; Using a normal distribution function to define the form of the surface settlement curve outside the pit at each target area; Comprehensively analyzing all the surface settlement curves outside the pit, using the preset multiple working condition models to predict the location of the maximum surface settlement outside the pit, and calculating the distance between the location of the maximum surface settlement outside the pit and the edge of the foundation pit; Determine the settlement impact range represented in the surface settlement curve outside the pit under each operating model; Based on the double-row spring model, the interaction between soil bodies is simulated, and the lateral displacement area of ​​the retaining structure is calculated according to the change in soil pressure inside and outside the foundation pit represented by the change in spring stiffness. A linear relationship model between the surface settlement area outside the pit and the lateral displacement area of ​​the retaining structure is established to predict the surface settlement outside the pit.

2. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 1 is characterized in that: Also includes: A prediction formula model based on the normal distribution function is obtained according to the maximum value of the surface settlement outside the pit and the normal distribution function to predict the settlement area of ​​the surface outside the pit.

3. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 2 is characterized in that: The multiple target areas include the front side of the subway station, the subway station and the back side of the subway station, and the surface settlement curve function outside the pit includes a curve segment in front of the subway station, a curve segment at the subway station and a curve segment behind the subway station.

4. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 3 is characterized in that: The surface settlement curve function outside the pit at each section of the target area is: In the formula, δ max Indicates the maximum value of surface settlement; x m Indicates the maximum position of surface settlement; x indicates the horizontal distance from the foundation pit; r indicates the impact radius, r = x0-x m ; x0 represents the settlement influence range.

5. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 4 is characterized in that: Establish the relationship between the maximum settlement values ​​of the three target areas: the front side of the subway station, the subway station, and the back side of the subway station: Where D is the distance between the foundation pit and the subway station; δmax(1), δmax(2), and δmax(3) are the maximum settlement values ​​of the surface settlement curve outside the pit in front of the subway station, at the subway station, and behind the subway station, respectively.

6. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 1 is characterized in that: The normal distribution function is used to define the surface settlement curve form outside the pit at each target area: historical surface settlement data outside the pit at different locations are obtained; The parameters of the normal distribution are estimated based on the acquired data and the normal distribution function is constructed to form the surface settlement curve outside the pit.

7. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 1 is characterized in that: Determine the settlement influence range under each working condition model specifically including: Preset and divide the main and secondary areas of settlement, and determine the critical positions of the main and secondary areas; According to the position of the critical point, define the relationship between the settlement amount at the critical point and the maximum settlement value of the surface outside the pit and obtain the settlement value at the position of the critical point according to the corresponding relationship; Taking the settlement value at the critical position as the entry point, combined with the settlement distribution under each working condition model, all positions in the settlement distribution where the settlement exceeds a preset threshold are identified to obtain the settlement influence range.

8. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 1 is characterized in that: The distance between the position of the maximum surface settlement outside the pit and the edge of the foundation pit is calculated as follows: According to the distance between the foundation pit and the subway station, calculate the distance between the maximum settlement position in front of the station and the edge of the foundation pit, and the distance between the maximum settlement position in the rear of the station and the edge of the foundation pit; The formula for the distance from the maximum position of the surface settlement outside the pit to the edge of the foundation pit under different spacings is: Where D represents the distance between the foundation pit and the subway station, Xm1 represents the distance between the maximum settlement position in front of the station and the edge of the foundation pit, Xm2 represents the distance between the maximum settlement position at the station and the edge of the foundation pit, and Xm3 represents the distance between the maximum settlement position at the rear of the station and the edge of the foundation pit.

9. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 5 is characterized in that: The linear relationship model between the surface settlement area outside the pit and the lateral displacement area of ​​the enclosure structure is established by analyzing the surface settlement area outside the pit and the lateral displacement area of ​​the enclosure structure in each working condition model; according to the surface settlement area outside the pit and the lateral displacement area of ​​the enclosure structure obtained in different working condition models, a unified linear relationship between the two is established: A w =αA sν Among them, A sν A is the surface settlement area outside the pit; w is the lateral displacement area value of the enclosure structure; α is the proportional relationship.

10. The method for foundation pit support design and deformation evaluation considering the barrier effect of existing underground structures according to claim 9, characterized in that: Obtaining a prediction formula model based on the normal distribution function according to the maximum value of the surface settlement outside the pit and the normal distribution function specifically includes: Substitute the maximum value of the surface settlement outside the pit into the assumed normal distribution function to solve the prediction formula for the surface settlement area outside the pit: X 车站 Where erf is the error function, Indicates the horizontal distance between the station and the foundation pit; Based on the relationship between the surface settlement area outside the pit and the area of ​​the enclosure structure A w =αA sν The relationship between the maximum settlement values ​​of the three target areas, namely, the front side of the subway station, the subway station and the rear side of the subway station, is calculated to obtain the maximum surface settlement δmax(1) outside the pit in front of the subway station and the lateral displacement area of ​​the enclosure A. w relationship; The prediction formula for the maximum value of the surface settlement outside the pit in front of the subway station, δmax(1), is obtained as follows: Based on the prediction formula of the maximum value of the surface settlement outside the pit δmax(1) in front of the subway station and the relationship between the maximum settlement values ​​of the three target areas in front of the subway station, at the subway station and behind the subway station, the prediction formula of the maximum value of the surface settlement outside the pit δmax(2) at the subway station and the prediction formula of the maximum value of the surface settlement outside the pit δmax(3) at the back of the subway station are respectively obtained.

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