A method for determining support parameters of inclined piles based on a corner region of a foundation pit

Abstract

The present application relates to the application technology of inclined pile support, and discloses a kind of inclined pile support parameter determination method based on foundation pit external corner area, first, the boundary support of both sides of external corner is demarcated to lock the support range to be distributed, then the initial position of external corner support is determined, the support span is calculated in combination with horizontal spacing between piles, external corner vertical center distance of foundation pit and support type correction coefficient, the axial force of inclined pile is solved according to this, and the bearing capacity is checked, if not satisfied, adjust the layout parameters to form the support scheme by iteration optimization.The present application divides three kinds of external corner working conditions according to the size of external corner and the number of solid angle support, and uses different reduction parameters to distinguish steel sheet pile and conventional support, which is consistent with the stress characteristics of external corner space;For short pile in design stage and pile encountering obstacle in construction stage, span inversion distribution and pile combination bearing scheme for pile encountering obstacle are respectively proposed;At the same time, support pre-axial force is given, and compensation loading is implemented according to the measured axial force of boundary support, which matches the measured axial force on site, can reduce support rework, and improve the deformation control accuracy of foundation pit.

Description

Technical Field

[0001] This invention relates to inclined pile support application technology, and more specifically to a method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit. Background Technology

[0002] Inclined pile bracing is a type of support system that uses inclined piles to transfer the horizontal load borne by the foundation pit support structure to the lower soil layers. During the design and construction of foundation pit projects, it is typically necessary to determine the support range and axial load borne by each inclined pile brace by considering factors such as the horizontal load borne by the support structure, the spacing of the inclined pile braces, the brace inclination angle, and the bearing capacity of the inclined pile braces.

[0003] In foundation pit engineering, when a corner appears at the boundary of the foundation pit, it is usually called the external corner area. The external corner area is different from the ordinary continuous support section. The support structures on both sides of the external corner area are spatially connected to each other, forming a stress area with spatial effect.

[0004] For inclined pile supports continuously arranged along a straight section of the foundation pit, the force boundaries between adjacent supports are relatively clear, and the calculated span borne by each inclined pile support can be allocated according to the arrangement relationship between adjacent supports. However, in the external corner area of ​​the foundation pit, since the two adjacent sides of the foundation pit meet at the corner, a spatial force relationship is formed between the inclined pile supports in the external corner area. The horizontal support range borne by the target inclined pile support is not only affected by the distance between it and the adjacent inclined pile supports, but also by the geometric dimensions of the external corner and the support structure characteristics of the external corner area.

[0005] In addition, different external corner areas may have different arrangements such as small external corners, single horizontal corner bracing, or multiple horizontal corner bracing. The lateral deformation characteristics of different support structures also differ, which may lead to deviations between the design calculation results and the actual stress state when a unified calculation span allocation method is adopted. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for determining the parameters of inclined pile supports in the external corner area of ​​a foundation pit. This method first determines the supports on both sides of the external corner area, thereby defining the range to be allocated for support. Then, within the range to be allocated for support, the calculated span and support parameters of the target external corner support are determined. This method ensures that the parameter determination of the target external corner support has a clear spatial boundary and allows for adjustments to the arrangement or configuration of the target external corner support based on different external corner support conditions and the influence of obstacles.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit includes: S1. Obtain the geometric parameters and support parameters of the target external corner area, first determine the planar positions of the first boundary support and the second boundary support set on both sides of the target external corner area, and limit the support range to be allocated by the two. S2. Determine the initial position of the target corner support within the range to be allocated, obtain the first horizontal distance between the target corner support and the first boundary support, and the second horizontal distance between the target corner support and the second boundary support, and determine the center distance reduction parameter according to the support structure type. The center distance reduction parameter is specifically a correction coefficient used to adjust the influence of the center distance of the corner in the vertical direction of the foundation pit on the calculated span of the target corner support. S3. Based on the first horizontal spacing, the second horizontal spacing, the center distance of the external corner perpendicular to the foundation pit and the center distance reduction parameter, determine the calculation span of the target external corner support according to the calculation span determination rule; S4. Determine the standard value of axial load based on the calculated span, horizontal load parameters and target external corner support inclination angle, and determine whether the preset bearing conditions are met based on the standard value of axial load, the standard value of single pile axial compressive ultimate bearing capacity and the foundation pit safety level. S5. If the preset bearing conditions are not met, keep the planar position of the two boundary supports unchanged, adjust the arrangement parameters and / or support configuration of the target corner support, and redetermine the calculated span and judge the preset bearing conditions until the preset bearing conditions are met. S6. Based on the target corner support parameters and the support parameters of the two boundary supports that meet the preset bearing conditions, a sloping pile support scheme for the target corner area is formed.

[0008] In this invention, preferably, the first boundary support and the second boundary support are inclined pile supports located on both sides of the support range to be allocated and whose planar positions have been determined before the target corner support is determined. The calculated span borne by each boundary support is determined based on the horizontal distance between each boundary support and its adjacent support, and the standard value of the axial load of the corresponding boundary support is determined based on the calculated span, the horizontal load parameters, and the inclination angle of the corresponding boundary support.

[0009] In this invention, preferably, the rule for determining the span of the target support at the external angle includes: The initial horizontal support range corresponding to the target corner support is determined based on the first horizontal spacing and the second horizontal spacing. The center distance of the external corner in the direction of the vertical foundation pit is corrected according to the center distance reduction parameter, and the initial horizontal support range is deducted using the corrected center distance of the external corner in the direction of the vertical foundation pit, so as to determine the calculated span borne by the target external corner support. When adjusting the arrangement parameters of the target external corner support, the sum of the first horizontal spacing and the second horizontal spacing and / or the center distance of the external corner in the direction perpendicular to the foundation pit changes.

[0010] In this invention, preferably, when the target corner support is supported by short inclined piles due to obstacles during the design phase, the calculated span that the short inclined pile support can bear is determined according to the standard value of the single pile axial compressive ultimate bearing capacity, horizontal load parameters, support inclination angle, and foundation pit safety level of the short inclined pile support, and the short pile calculation span inversion rule; the short pile calculation span inversion rule refers to the calculation process of using the bearing capacity of the short inclined pile support as a constraint and solving the allowable calculated span of the short inclined pile support in reverse according to the bearing judgment relationship. The remaining calculated span in the support area to be allocated, excluding the calculated span borne by the short inclined pile support, is allocated to the long inclined pile support adjacent to the short inclined pile support.

[0011] In this invention, preferably, when the target corner support encounters an obstacle during the construction phase and forms an obstacle pile, a supplementary pile is set in the area corresponding to the obstacle pile, and the obstacle pile and the supplementary pile are determined as a combined support; The combined bearing parameters of the combined support are determined based on the standard values ​​of the axial compressive ultimate bearing capacity of the single piles of the obstacle piles and the supplementary piles, and the bearing conditions of the combined support are judged according to the calculated span corresponding to the original support position of the target corner support.

[0012] In this invention, preferably, the center distance reduction parameter is determined based on the statistical results of the axial force ratio of multiple external corner inclined pile support samples; the axial force ratio is determined based on the maximum measured axial force of each external corner inclined pile support sample during the foundation pit excavation stage and the standard value of axial load determined according to the corresponding calculated span, and the first reduction parameter and the second reduction parameter are determined respectively based on the statistical results of the axial force ratio corresponding to different support structure types.

[0013] In this invention, preferably, when the target external angle area is a non-sheet pile supported area, the center distance reduction parameter is determined as a first reduction parameter; when the target external angle area is a sheet pile supported area, the center distance reduction parameter is determined as a second reduction parameter that is less than the first reduction parameter.

[0014] In this invention, preferably, the horizontal corner bracing configuration information of the target external corner area is obtained, and the external corner type is determined according to the center distance of the external corner in the direction perpendicular to the foundation pit and the horizontal corner bracing configuration information; When the center distance of the external corner perpendicular to the foundation pit is not greater than the preset center distance threshold and no horizontal corner bracing is provided, it is determined to be a small external corner; When the center distance of the external corner in the direction perpendicular to the foundation pit is greater than the preset center distance threshold and a horizontal corner brace is set, it is determined to be an external corner with a single corner brace. When at least two horizontal corner braces are installed, it is determined that the corner is an external corner with multiple corner braces.

[0015] In this invention, preferably, when forming the inclined pile support scheme, the corresponding target preload axial force is determined according to the standard value of the axial load of the first boundary support, the second boundary support and the target corner support, and the target preload axial force is 80% to 100% of the standard value of the corresponding axial load.

[0016] In this invention, preferably, after applying a pre-applied axial force to the target external corner support, the actual axial forces of the first boundary support and the second boundary support are obtained, and it is determined whether to perform compensation loading based on the axial force deviation between the actual axial force of each boundary support and the corresponding target axial force; when the axial force deviation meets the preset compensation condition, compensation loading is performed on the corresponding boundary support.

[0017] The beneficial effects of this invention are: The present invention first determines the first boundary support and the second boundary support, and uses the two boundary supports to limit the range of support to be allocated for the target corner support, so that the calculated span and support parameters of the target corner support are configured within the determined spatial boundary, thereby establishing the parameter transfer relationship between the two boundary supports and the target corner support.

[0018] This invention determines the calculated span of the target corner support based on the horizontal distance between the target corner support and the supports on both sides, the center distance of the corner in the direction perpendicular to the foundation pit, and the type of support structure. This allows the spatial geometric characteristics of the corner area and different support structure conditions to participate in the determination of the calculated span of the target support, thereby improving the matching degree between the support parameters of the corner area and the actual stress state.

[0019] When the target corner support is restricted by obstacles and short inclined pile support is used, the present invention can redistribute the calculated span within the range to be allocated support according to the actual bearing capacity of the short inclined pile support, avoiding the allocation of an excessively large support range to the short inclined pile support with limited bearing capacity in the same way.

[0020] When obstacles are encountered during the construction phase, by setting up supplementary piles and using the obstacles and supplementary piles as a combined support, the required support capacity at that location can be restored while maintaining the original support location corresponding to the calculated span. This reduces the impact of readjusting the support layout of the entire external corner area due to the inability of a single inclined pile to continue pile formation.

[0021] Furthermore, after applying pre-loaded axial force to the target corner support, the axial force coupling effect generated during the loading process of adjacent inclined pile supports can be further considered by re-acquiring the axial force of the supports on both sides and performing necessary compensation loading. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of the target support arrangement for the small positive corner in this invention; Figure 3 This is a schematic diagram of the target support arrangement of the external corner + single corner brace in this invention; Figure 4 This is a schematic diagram of the target support arrangement of the external corner + multiple corner braces in this invention; Figure 5 This is a schematic diagram of the calculation span allocation of long and short inclined pile supports in the design phase of this invention; Figure 6 This is a schematic diagram of the pile replacement method when encountering obstacles during the construction phase of this invention; Figure 7 This is a flowchart of the boundary support axial force verification process after the target support is loaded in this invention.

[0023] Attached reference numerals: 1. First boundary support; 2. Second boundary support; 3. Target corner support; 31. Short inclined pile; 32. Obstacle pile; 33. Supplementary pile; 4. Single corner brace; 5. Multiple corner braces. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are used to illustrate the technical solution of the present invention, and are not intended to limit the scope of protection of the present invention.

[0025] like Figure 1 As shown, this embodiment provides a method for determining the parameters of inclined pile support based on the external corner area of ​​a foundation pit. The method includes the following processes: determining the boundary support, initial configuration of the target external corner support, determining the calculated span of the target external corner support, judging the axial load and bearing conditions, adjusting the target external corner support, and forming the inclined pile support scheme.

[0026] To facilitate the explanation of the support parameter allocation relationship in this embodiment, such as Figure 2 As shown, the inclined pile supports that have completed the determination of planar position and support parameters before the target corner support is determined, and are located on both sides of the target corner area respectively, are defined as the first boundary support and the second boundary support.

[0027] The first and second boundary supports are not required to be the two outermost inclined pile supports in the entire external corner area, but rather refer to the two inclined pile supports used to provide the spatial boundaries on both sides during the determination of the current target external corner support parameters.

[0028] The corner area defined by the planar positions of the first and second boundary supports, which requires further configuration of target corner supports and calculation of span allocation, is defined as the support range to be allocated. The term "support range to be allocated" is a definition used in this embodiment to describe the parameter allocation relationship between supports, and does not indicate the formation of a separate solid structure in the foundation pit support structure.

[0029] The target corner support is located within the area to be allocated for support. The target corner support is not required to be located at the geometric midpoint between the first boundary support and the second boundary support; its specific location is further determined based on the corner geometry, support arrangement conditions, and load-bearing conditions.

[0030] Example 1: This embodiment combines Figures 1-4 Explain the process of determining the support parameters of the target's external angle under normal circumstances.

[0031] S1. Determine the first boundary support and the second boundary support.

[0032] Obtain the geometric parameters and support parameters of the external corner of the target external corner area, and first determine the planar position and support parameters of the first boundary support and the second boundary support.

[0033] The geometric parameters of the external corner include at least the center distance of the external corner in the direction perpendicular to the foundation pit; the support parameters may include the support structure type, horizontal load parameters, support inclination angle, support arrangement position, horizontal corner brace configuration, and the standard value of the axial compressive ultimate bearing capacity of a single pile of the inclined pile support.

[0034] like Figures 2 to 4 As shown, after the first and second boundary supports are determined, they jointly define the support range to be allocated corresponding to the target corner support. This embodiment adopts the method of first determining the two side boundary supports and then determining the target corner support. The reason for this is that the calculation span of the target corner support needs to be determined based on the horizontal distance between it and the adjacent inclined pile supports on both sides. When the two side boundary supports have not yet been determined, the spatial boundaries on both sides corresponding to the target corner support are also not determined, and the corresponding calculation span lacks stable geometric input conditions. Therefore, in this embodiment, the first and second boundary supports not only serve as spatial location references but also as boundary constraints for the subsequent allocation of the target corner support's calculation span.

[0035] During the determination of the target external corner support parameters, it is preferable to keep the planar positions of the first boundary support and the second boundary support unchanged. It should be noted that keeping the planar positions unchanged does not mean that all operating parameters of the first boundary support and the second boundary support remain unchanged. For example, after the pre-applied axial force is applied subsequently, the pre-applied axial force of the boundary support can still be adjusted to compensate for changes in the actual axial force.

[0036] For the first and second boundary supports themselves, their calculated span can be determined based on the distance between the location of the inclined pile support and the adjacent inclined pile support.

[0037] When the inclined pile support is located at the boundary with the horizontal support scheme and is rigidly connected to the capping beam, or when the inclined pile support is located in the middle area of ​​a continuous arrangement of inclined pile supports, its calculated span can be determined as follows: , When the inclined pile support is located in an area where the end is cantilevered or disconnected from other support forms, i.e., a non-rigid connection, its calculated span can be determined as follows: , in, For the calculation span corresponding to the inclined pile support, , , and The horizontal spacing is determined based on the planar positional relationship between the corresponding inclined pile support and the adjacent support.

[0038] S2. Determine the initial parameters of the target external corner support.

[0039] Set the initial position of the target corner support within the support area to be allocated, defined by the first boundary support and the second boundary support.

[0040] like Figures 2 to 4 As shown, the first horizontal spacing is determined based on the planar positional relationship between the target corner support and the first boundary support. The second horizontal spacing is determined based on the planar positional relationship between the target corner support and the second boundary support. At the same time, the center distance b in the direction perpendicular to the foundation pit at the external corner is obtained.

[0041] Furthermore, the type of external corner is determined based on the center distance of the external corner in the direction perpendicular to the foundation pit and the configuration information of the horizontal corner bracing in the external corner area.

[0042] like Figure 2 As shown, when the center distance b between the external corner and the foundation pit is not greater than 3.5m and no horizontal support is set in the external corner area, the external corner is defined as a small external corner.

[0043] like Figure 3 As shown, when the center distance b between the external corner and the foundation pit is greater than 3.5m and a horizontal corner brace is installed at the external corner, the external corner is defined as an external corner with a single corner brace.

[0044] like Figure 4 As shown, when two or more horizontal corner braces are installed at the external corner, the external corner is defined as an external corner with multiple corner braces.

[0045] The above three types of external angle configurations can use a unified method for determining the external angle span, but different center distance reduction parameters are used for different support structure types.

[0046] In this embodiment, when the target external corner area is not a sheet pile supported area, the center distance reduction parameter η is taken as 1.0; when the target external corner area is a sheet pile supported area, the center distance reduction parameter is... Take 0.6.

[0047] S3. Determine the span of the target external corner support.

[0048] The calculated span of the target external corner support is determined according to the following formula: , in: The calculated span for the support of the target external corner; The first horizontal distance between the target corner support and the first boundary support; b is the second horizontal distance between the target corner support and the second boundary support; b is the center distance of the corner in the direction perpendicular to the foundation pit. This is the center distance reduction parameter.

[0049] It should be noted that the calculation object in the original calculation relationship was the calculation span of the corner inclined pile support. To distinguish the target corner support from other inclined pile supports in this embodiment, the calculation span of the target corner support is denoted as... This symbol adjustment is only used to distinguish the calculation objects and does not change the original calculation relationship.

[0050] The above relationship indicates that the calculated span borne by the target corner support is not simply distributed equally according to the distance between the first boundary support and the second boundary support, but simultaneously considers the first horizontal spacing, the second horizontal spacing, and the center distance of the corner in the direction perpendicular to the foundation pit.

[0051] For the sheet pile supported area, the center distance reduction parameter is 0.6. Compared with the non-sheet pile supported area, the effect of the center distance of the external corner in the direction perpendicular to the foundation pit in the deduction item is reduced, thereby increasing the calculated span and correspondingly increasing the standard value of the axial load of the target external corner support determined according to the calculated span, so as to reflect the influence of the low lateral stiffness of the sheet pile supported area and the external corner spatial effect on the actual support axial force.

[0052] Furthermore, based on the above calculation relationship, it can be determined that when only the position of the target corner support within a certain fixed interval is changed, while the sum of the first horizontal spacing and the second horizontal spacing and the center distance of the corner perpendicular to the foundation pit remain unchanged, the calculated span obtained according to the above relationship also remains unchanged.

[0053] Therefore, the change in the calculated span of the target corner support by adjusting the plane arrangement in this embodiment means that the plane arrangement adjustment causes the sum of the first horizontal spacing and the second horizontal spacing and / or the center distance of the corner perpendicular to the foundation pit to change, rather than simply changing the position of the target corner support.

[0054] The above conclusions are mathematical results obtained directly from the relationship determined by calculating the span of the target support at the positive angle, and do not belong to the empirical calculation model introduced separately.

[0055] S4. Determine the axial load of the target external corner support and perform load-bearing assessment.

[0056] After determining the calculated span of the target corner support, the standard value of the axial load of the target corner support is determined based on the calculated span borne by the target corner support, the standard value of the horizontal force within the calculated width of the retaining structure, and the inclination angle between the target corner support and the horizontal direction. The standard value of the axial load of the target corner support is determined according to the following formula: , in: The standard value of the axial load for the target external corner support; Calculate the standard value of the horizontal force within the width of the retaining structure; The angle between the target external corner support and the horizontal direction.

[0057] Furthermore, based on the standard value of the ultimate axial compressive bearing capacity of the single pile of the target corner support and the safety level of the foundation pit, it is determined whether the target corner support meets the preset bearing conditions. The target corner support is deemed to meet the preset bearing conditions when the following conditions are met: , in, The standard value of the axial compressive ultimate bearing capacity of a single pile for the target external corner support; This refers to the safety factor corresponding to the safety level of the excavation pit. For Class I, II, and III excavations, We take values ​​of 1.8, 1.6, and 1.4 respectively.

[0058] This embodiment uses the standard value of the axial compressive ultimate bearing capacity of a single pile as an existing support bearing parameter, such as the existing design parameters or bearing capacity test results of the corresponding inclined pile support. This embodiment uses the standard value of the axial compressive ultimate bearing capacity of a single pile to determine the support span and bearing conditions in the corner area, without further limiting the internal calculation method of the standard value of the axial compressive ultimate bearing capacity of the single pile.

[0059] S5. Adjust the target external corner support.

[0060] When the judgment result of S4 indicates that the target corner support meets the preset bearing conditions, the current target corner support parameters can be retained. When the target corner support does not meet the preset bearing conditions, the target corner support is adjusted while keeping the planar positions of the first and second boundary supports unchanged. Under normal corner arrangement conditions, the target corner support arrangement parameters, which can change the first horizontal spacing, the second horizontal spacing, the center distance of the corner in the direction perpendicular to the foundation pit, and / or the support inclination angle, can be adjusted.

[0061] When the adjustment results change the first horizontal spacing, the second horizontal spacing, or the center distance of the external corner perpendicular to the foundation pit, the calculation span of the target external corner support is recalculated using the relationship determined in S3. When the inclination angle of the target external corner support is adjusted, the standard value of the axial load of the target external corner support is recalculated based on the adjusted inclination angle. After each effective parameter adjustment is completed, S3 and S4 are executed again until the target external corner support meets the preset bearing conditions.

[0062] It should be noted that when obstacles exist in the design phase, which means that only short piles can be used for the target corner support, or when obstacles are encountered during the construction phase, the above-mentioned continuous parameter adjustments are not simply made. Instead, the calculation span is redistributed or the combined support is reconstructed according to Example 3 and Example 4, respectively.

[0063] S6. Form a sloping pile support scheme for the external corner area.

[0064] Once the target corner support meets the preset bearing conditions, the corresponding target corner support parameters are determined as valid target support parameters. Based on the planar positions and support parameters of the first boundary support, the second boundary support, and the target corner support, a sloped pile support scheme for the target corner area is formed.

[0065] The inclined pile support scheme may include the planar positions of the first boundary support and the second boundary support, the planar position of the target external corner support, the first horizontal spacing, the second horizontal spacing, the center distance of the external corner in the direction perpendicular to the foundation pit, the center distance reduction parameter, the calculated span of the target external corner support, the inclination angle of the target external corner support, the standard value of the axial load of the target external corner support, and the standard value of the corresponding single pile axial compressive ultimate bearing capacity.

[0066] This leads to the process of determining the support parameters for the corner area by first determining the boundary support, then limiting the range of support to be allocated, configuring the target corner support, determining the calculated span, judging the load-bearing capacity, and adjusting the target corner support.

[0067] Example 2: To determine reasonable values ​​for the center-distance reduction parameter under different support structure types, the method for determining the calculated span can be evaluated based on the measured axial forces of inclined pile supports at external corners in multiple actual foundation pit projects. The axial force ratio of the inclined pile support is determined according to the following formula: , in, This refers to the axial force ratio of the inclined pile support; This represents the maximum measured value of the axial force of the inclined pile support during the foundation pit excavation stage. This represents the standard value of the axial load determined according to the corresponding calculated span. The axial force ratio is used to characterize the degree of matching between the standard value of the axial load obtained according to the corresponding calculated span and the actual maximum axial force.

[0068] In the small positive corner sample in the non-steel sheet pile support area, the standard value of the horizontal force within the calculated width of the retaining structure is 152kN / m, the first horizontal spacing is 6.8m, the second horizontal spacing is 8.1m, the center distance of the positive corner in the direction perpendicular to the foundation pit is 1.3m, and the calculated span is 6.8m after reducing the center distance by 1.0. The corresponding standard value of the axial load is 1462kN, the maximum measured axial force is 1382kN, and the axial force ratio is 0.95.

[0069] In a sample with a single corner bracing at an external corner, the standard value of the horizontal force within the calculated width of the retaining structure is 120 kN / m. The first and second horizontal spacings are both 8.7 m. The center distance between the external corner and the foundation pit is 3.8 m. After reducing the center distance by 1.0, the calculated span is 6.8 m, corresponding to a standard value of 1154 kN for the axial load. The maximum measured axial force is 1213 kN, and the axial force ratio is 1.05.

[0070] In another sample with a single corner brace at an external corner, the first horizontal spacing is 6.1m, the second horizontal spacing is 9.1m, the center distance of the external corner in the direction perpendicular to the foundation pit is 4.6m, the calculated span is 5.3m, the corresponding standard value of axial load is 1199kN, the maximum measured axial force is 1579kN, and the axial force ratio is 1.32.

[0071] In the sample with multiple corner bracing at the external corner, the first horizontal spacing is 7.8m, the second horizontal spacing is 26.7m, the center distance of the external corner in the direction perpendicular to the foundation pit is 17.2m, and the span is calculated to be 8.65m after reducing the center distance by 1.0. The corresponding standard value of axial load is 1345kN, the maximum measured axial force is 1448kN, and the axial force ratio is 1.08.

[0072] Samples of inclined pile supports at external angles in multiple non-sheet pile supported areas show that, when using a center-distance reduction parameter of 1.0, the measured axial force ratio generally reflects the correspondence between the actual force and the calculated value. For sheet pile supported areas, due to their relatively low lateral stiffness and the spatial effect in the external angle area, directly using the same center-distance reduction parameter as in non-sheet pile supported areas may underestimate the actual stress level of the inclined pile supports at external angles.

[0073] In two sheet pile-supported area samples, when the center-distance reduction parameter was 1.0, the axial force ratios reached 1.64 and 2.55, respectively. After adjusting the center-distance reduction parameter corresponding to the center-distance perpendicular to the foundation pit at the external corner to 0.6, the axial force ratios of the two samples were approximately 0.99 and 0.96, respectively, close to 1.0. Therefore, in this embodiment, a center-distance reduction parameter of 1.0 is used for non-sheet pile-supported areas, and a center-distance reduction parameter of 0.6 is used for sheet pile-supported areas.

[0074] It should be noted that the center distance reduction parameter of 0.6 does not mean changing the rigidity of the sheet pile itself, but rather it is used to correct the influence of the center distance in the direction of the external corner perpendicular to the foundation pit in the process of determining the span, so that the standard value of axial load obtained according to the calculated span is more in line with the actual stress state of the external corner area of ​​the sheet pile.

[0075] Example 3: In the aforementioned process of determining the support parameters for the external corner area, when the target external corner support cannot be constructed according to the design length due to underground obstacles, the analysis is still based on the external corner support range defined by the first and second boundary supports, and the calculated span that the target external corner support can bear is re-determined according to the actual bearing capacity of the short inclined piles. For example... Figure 5 As shown, when the design phase has determined that there are engineering piles or other underground obstacles at the target corner support location, making it impossible to set the target corner support according to the predetermined pile length, the target corner support can be designed as a short inclined pile support.

[0076] At this point, since the standard value of the axial compressive ultimate bearing capacity of a single pile of the short inclined pile support may be lower than that of the adjacent long inclined pile support, the method of equally dividing the support area to be allocated by long and short piles is not adopted. Instead, the calculated span that the short inclined pile support can bear is first calculated based on its own standard value of the axial compressive ultimate bearing capacity of a single pile. The calculated span that the short inclined pile support can bear satisfies: , in: This indicates the calculated span that the short inclined pile support can withstand; This represents the standard value of the ultimate axial compressive bearing capacity of a single pile supported by short inclined piles; The safety factor corresponding to the safety level of the foundation pit; Calculate the standard value of the horizontal force within the width of the retaining structure; The angle between the short inclined pile support and the horizontal direction is given. The above formula directly determines the calculated span that the short inclined pile support can bear based on its existing bearing capacity.

[0077] After determining the calculated span that the short inclined pile support can bear, the remaining calculated span in the support range to be allocated is distributed to the long inclined pile support adjacent to the short inclined pile support, thus forming a non-equal calculation span distribution between the long pile and the short pile.

[0078] For example, in the three sets of measured samples of long and short inclined pile supports, their axial force ratios were 1.17, 0.92 and 1.13, respectively, with an average of about 1.07, which is close to the average axial force ratio of 1.05 for inclined pile supports in the normal area. This indicates that the method of inverting the calculated span borne by the short inclined pile support based on the standard value of its ultimate bearing capacity and then distributing the remaining span to the long inclined pile support can better adapt to the situation where the bearing capacities of long and short inclined pile supports are different.

[0079] Example 4: When the target corner support cannot form a complete single-pile support due to obstacles, a new target corner support system is formed by combining the obstacle pile with the supplementary pile, while maintaining the boundary support relationship of the corner area. For example... Figure 6 As shown, when the target corner support encounters old piles, old foundations, engineering piles, or other underground obstacles at the bottom of the pile during the construction phase, making it impossible for the inclined pile support to continue as originally designed, the support is identified as an obstacle-encounter pile. A supplementary pile is added in the corresponding area of ​​the obstacle-encounter pile. The two short piles, the obstacle-encounter pile and the supplementary pile, are considered as a combined support, and their combined bearing parameters are determined according to the following formula: , in: This refers to the standard value of the ultimate axial compressive bearing capacity of a single pile with combined support. This is the standard value of the axial compressive ultimate bearing capacity of a single pile encountering an obstacle; This refers to the standard value of the axial compressive ultimate bearing capacity of a single pile used for supplementary piles.

[0080] The combined support continues to correspond to the calculated span of the original target corner support location, instead of redividing the entire unallocated support range between the first and second boundary supports due to the obstruction of the construction of one of the inclined piles.

[0081] The bearing capacity is reassessed based on the combined bearing parameters of the combined support and the calculated span corresponding to the original target corner support location. When the combined support meets the corresponding bearing capacity, the obstacle pile and the supplementary pile are included together as the combined support at the original target corner support location in the inclined pile support scheme of the target corner area.

[0082] Therefore, this method can reconfigure the support structure for local pile formation anomalies that occur during the construction phase while keeping the support on both sides of the boundary and the support range corresponding to the original target support position basically unchanged.

[0083] Example 5: like Figure 7As shown, when using preloaded inclined pile supports, the corresponding target preloaded axial force is determined based on the standard values ​​of the axial loads of the first boundary support, the second boundary support, and the target corner support. The target preloaded axial force is preferably determined according to 80% to 100% of the corresponding standard value of the axial load. For foundation pits with sensitive surrounding environments or high deformation control requirements, a target preloaded axial force close to the upper limit of the range can be used. Here, the range of 80% to 100% of the standard value of the axial load is directly used, without introducing a separate formula for calculating the preload ratio.

[0084] After applying a pre-stressed axial force to the target corner support, the actual axial forces of the first and second boundary supports are obtained and compared with the corresponding target axial forces. Since the first boundary support, the target corner support, and the second boundary support are connected by the capping beam and other support structures, loading the target corner support may cause changes in the axial forces of the already loaded boundary supports. When the deviation between the actual axial force and the target axial force of the first or second boundary support reaches a preset compensation condition, compensation loading is applied to the corresponding boundary support.

[0085] In the adjacent inclined pile support loading test, when the adjacent inclined pile supports are loaded to 0.5 times the standard value of the axial compressive ultimate bearing capacity of a single pile, the pre-loaded axial force attenuation coefficient of the loaded inclined pile supports is in the range of 0.87 to 0.95. Approximately 0.9 can be used as an engineering reference value for this loading stage. When loading is performed with an interval of one inclined pile support, the impact on the loaded supports is relatively small. It should be noted that the above-mentioned 0.87 to 0.95 and 0.9 correspond to specific loading test conditions. In this embodiment, it is preferable to determine whether to perform compensatory loading based on the actual monitored axial force deviation, rather than using 0.9 as a fixed compensation parameter for all working conditions.

[0086] Through the above processing, a coordinated control process of target support loading, boundary support axial force verification, and compensation adjustment can be further formed after the target corner support configuration is completed.

[0087] In summary, this invention first uses first and second boundary supports to define the range of support to be allocated in the external corner area, and then determines the target external corner support within the range of support to be allocated. The calculated span of the target external corner support is determined based on the spatial configuration of the external corner and the type of support structure, and the parameters of the target external corner support are judged and adjusted based on the axial load and the support bearing capacity. When affected by obstacles during the design or construction phases, local support configuration adjustments can be made through non-equal span allocation of long and short piles and by supplementing piles to form combined supports, thereby forming a scheme for determining inclined pile support parameters suitable for different external corner configurations and abnormal support conditions.

[0088] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit, characterized in that, include: S1. Obtain the geometric parameters and support parameters of the target external corner area, first determine the planar positions of the first boundary support and the second boundary support set on both sides of the target external corner area, and limit the support range to be allocated by the two. S2. Determine the initial position of the target corner support within the range to be allocated, obtain the first horizontal distance between the target corner support and the first boundary support, and the second horizontal distance between the target corner support and the second boundary support, and determine the center distance reduction parameter according to the support structure type; S3. Based on the first horizontal spacing, the second horizontal spacing, the center distance of the external corner perpendicular to the foundation pit and the center distance reduction parameter, determine the calculation span of the target external corner support according to the calculation span determination rule; S4. Determine the standard value of axial load based on the calculated span, horizontal load parameters and target external corner support inclination angle, and determine whether the preset bearing conditions are met based on the standard value of axial load, the standard value of single pile axial compressive ultimate bearing capacity and the foundation pit safety level. S5. If the preset bearing conditions are not met, keep the planar position of the two boundary supports unchanged, adjust the arrangement parameters and / or support configuration of the target corner support, and redetermine the calculated span and judge the preset bearing conditions until the preset bearing conditions are met. S6. Based on the target corner support parameters and the support parameters of the two boundary supports that meet the preset bearing conditions, a sloping pile support scheme for the target corner area is formed. Wherein, the first boundary support and the second boundary support are inclined pile supports located on both sides of the support range to be allocated and whose planar positions have been determined before the target corner support is determined; The calculated span borne by each boundary support is determined based on the horizontal distance between each boundary support and its adjacent support, and the standard value of the axial load of the corresponding boundary support is determined based on the calculated span, the horizontal load parameters and the inclination angle of the corresponding boundary support. The rules for determining the span of the target support calculation at the positive angle include: The initial horizontal support range corresponding to the target corner support is determined based on the first horizontal spacing and the second horizontal spacing. The center distance of the external corner in the direction of the vertical foundation pit is corrected according to the center distance reduction parameter, and the initial horizontal support range is deducted using the corrected center distance of the external corner in the direction of the vertical foundation pit, so as to determine the calculated span borne by the target external corner support. When adjusting the arrangement parameters of the target corner support, the sum of the first horizontal spacing and the second horizontal spacing and / or the center distance of the corner in the direction perpendicular to the foundation pit changes. When the target corner support encounters an obstacle during the construction phase and forms an obstacle pile, a supplementary pile is set in the area corresponding to the obstacle pile, and the obstacle pile and the supplementary pile are determined as a combined support; The combined bearing parameters of the combined support are determined based on the standard values ​​of the axial compressive ultimate bearing capacity of the single piles of the obstacle piles and the supplementary piles, and the bearing conditions of the combined support are judged according to the calculated span corresponding to the original support position of the target corner support.

2. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 1, characterized in that, When the target corner support adopts short inclined pile support due to obstacle restrictions during the design stage, the calculated span that the short inclined pile support can bear is determined in reverse based on the standard value of the single pile axial compressive ultimate bearing capacity, horizontal load parameters, support inclination angle and foundation pit safety level of the short inclined pile support; The remaining calculated span in the support range to be allocated, excluding the calculated span borne by the short inclined pile support, is allocated to the long inclined pile support adjacent to the short inclined pile support.

3. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 1, characterized in that, The center distance reduction parameter is determined based on the statistical results of the axial force ratio of multiple external angle inclined pile support samples; the axial force ratio is determined based on the maximum measured axial force of each external angle inclined pile support sample during the foundation pit excavation stage and the standard value of axial load determined according to the corresponding calculated span, and the first reduction parameter and the second reduction parameter are determined respectively based on the statistical results of the axial force ratio corresponding to different support structure types.

4. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 3, characterized in that, When the target external angle area is a non-sheet pile supported area, the center distance reduction parameter is determined as the first reduction parameter; when the target external angle area is a sheet pile supported area, the center distance reduction parameter is determined as the second reduction parameter, which is less than the first reduction parameter.

5. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 1, characterized in that, Obtain the horizontal corner bracing configuration information of the target external corner area, and determine the external corner type based on the center distance of the external corner in the direction perpendicular to the foundation pit and the horizontal corner bracing configuration information; When the center distance of the external corner in the direction perpendicular to the foundation pit is not greater than the preset center distance threshold and no horizontal corner bracing is set, it is determined to be a small external corner; When the center distance of the external corner in the direction perpendicular to the foundation pit is greater than the preset center distance threshold and a horizontal corner brace is set, it is determined to be an external corner with a single corner brace. When at least two horizontal corner braces are installed, it is determined that the corner is an external corner with multiple corner braces.

6. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 1, characterized in that, When forming the inclined pile support scheme, the corresponding target preload axial force is determined according to the standard value of the axial load of the first boundary support, the second boundary support and the target corner support. The target preload axial force is determined according to the allowable preload range of the support structure.

7. The method for determining inclined pile support parameters based on the external corner area of ​​a foundation pit according to claim 6, characterized in that, After applying a pre-applied axial force to the target external corner support, the actual axial forces of the first boundary support and the second boundary support are obtained, and it is determined whether to perform compensation loading based on the axial force deviation between the actual axial force of each boundary support and the corresponding target axial force. When the axial force deviation meets the preset compensation conditions, compensation loading is performed on the corresponding boundary support.

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