A method for calculating and analyzing uplift stability of a narrow foundation pit adjacent to a river

Abstract

The present application provides a kind of river type narrow foundation pit anti-heave stability calculation method, by considering the blocking effect of circular sliding heave on side soil and supporting structure, introduce topographic related factors slope angle and river distance, and river level variation produces four parameters of force and seepage force to traditional calculation method, obtain the calculation result of river type narrow foundation pit anti-heave stability.The upper part of the soil in the soil outside the pit slope angle and river distance, and river level variation produces force and seepage force to pit.The upper part of the soil in the soil outside the pit slope angle and river distance two parameters are to reflect the uneven terrain problem of calculating the river type narrow foundation pit outside the pit soil, make up the defect that traditional method does not consider the pit outside terrain factor.The river level variation produces force and seepage force two parameters to pit in order to reflect the influence problem of calculating the river type narrow foundation pit outside the river, make up the advantage that traditional method does not consider the pit outside river influence factor.

Description

Technical Field

[0001] This invention relates to the field of foundation pit engineering, and mainly to a method for calculating the heave stability of narrow foundation pits near rivers. Background Technology

[0002] With national development, cities have numerous rivers and lakes, and urban construction projects are constantly being updated and iterated with the times. Due to urban ecological needs, most of these projects are located near urban rivers, inevitably resulting in narrow foundation pits. This is due to two main reasons: firstly, urban development leads to urban space congestion, limiting the space for foundation pit excavation; secondly, these projects are typically narrow and elongated, built along riverbanks. The main failure mode for narrow foundation pits near rivers is circular arc sliding and bottom heave failure, where the soil heave is simultaneously hindered by the opposite soil and the support structure. Furthermore, the soil displacement patterns, support structure stress characteristics, and deformation characteristics of these narrow, elongated foundation pits differ from those of wider foundation pits due to the influence of the upper topography and water level. Currently, relevant national standards, papers, and patents for foundation pit construction lack specific calculation formulas related to the support of narrow foundation pits near urban rivers. Therefore, using traditional calculation methods leads to inconsistencies with actual conditions, potentially causing safety accidents and economic losses. Summary of the Invention

[0003] To address the shortcomings of existing calculation methods, this invention provides a method for calculating the heave stability of narrow, river-adjacent foundation pits. By considering the obstructing effect of circular arc sliding heave on the lateral soil and support structure, it introduces four parameters related to topography: slope angle and distance from the river, as well as the forces and seepage forces exerted on the foundation pit by river level fluctuations. These parameters are then incorporated into the traditional calculation method to obtain the heave stability calculation results for narrow, river-adjacent foundation pits. Compared to traditional calculation methods, this invention adds four parameters: the slope angle of the upper and middle soil outside the pit and the distance from the river, as well as the forces and seepage forces exerted on the foundation pit by river level fluctuations. The slope angle of the upper and middle soil outside the pit and the distance from the river are used to reflect the unevenness of the terrain outside the foundation pit, compensating for the deficiency of traditional calculation methods that do not consider external topographical factors. The forces and seepage forces exerted on the foundation pit by river level fluctuations are used to reflect the influence of external rivers on narrow, river-adjacent foundation pits, providing an advantage over traditional calculation methods by considering the influence of external rivers.

[0004] To achieve the above objectives, this invention provides a method for calculating and analyzing the heave stability of a narrow, river-adjacent foundation pit. The method includes the following steps:

[0005] Step 1: Establish a model of a narrow, river-adjacent foundation pit, including the slope section AC, the straight section CD, the circular section DEF, the circular section FG, the straight section GJ, the upper load q, the upper soil CAPOD region, and the circular sliding section DEKO region; the intersection point C of the circular sliding surface of the upper soil CAPOD region with the riverbank slope, and the river water level at a height h above the ground. w ,

[0006] Among them, when the pile length L ≤ the pit width B, it is defined as a narrow pit;

[0007] Among them, the circular sliding radius of the narrow foundation pit is R=B, the center O is located at the lower part of the intersection of the pit bottom and the support structure, and the buried depth is O=H+LR, where H is the excavation depth of the foundation pit and L is the pile length;

[0008] Step 2: Based on the established model, the following parameters are introduced as calculation parameters for the heave stability calculation and analysis method of narrow foundation pits near rivers: slope angle α, distance from the river b, and the force F generated by river water level fluctuations on the foundation pit. w The seepage force J generated by river water level changes on the foundation pit;

[0009] Step 3: Based on the model from Step 1 and the parameters from Step 2, calculate the anti-sliding moment MR1 generated by slope segment AC on the circular sliding surface; calculate the anti-sliding moment MR2 generated by the straight section CD of the foundation pit on the circular sliding surface; calculate the anti-sliding moment MR3 generated by the circular sliding surface DEF of the foundation pit on the circular sliding surface; calculate the anti-sliding moment MR4 generated by the circular sliding surface FG of the foundation pit on the circular sliding surface; calculate the sliding moment MS1 generated by the upper load q at the distance b from the river and the self-weight of the upper soil CAPOD region; calculate the sliding moment MS2 generated by the self-weight of the soil DEKO region of the circular sliding segment; and calculate the riverbank force F. W Sliding torque MSW F The sliding moment MSW of the river on the seepage force J of the foundation pit f ;

[0010] Step 4: Based on the parameters MR1, MR2, MR3, MR4, MS1, MS2, and MSW calculated in Step 3... F and MSW f The total anti-sliding moment MR and the total sliding moment MS were calculated, and finally the heave stability coefficient k of the narrow excavation pit near the river was obtained. s ;

[0011] Among them, the sliding moment is mainly provided by the upper load q acting at the distance b from the river, the self-weight of the upper soil CAPOD region, and the self-weight of the soil DEKO region of the circular sliding section.

[0012] The slope angle α and the distance to the river b can be used to quantitatively calculate the degree of unevenness of the soil outside the narrow foundation pit near the river.

[0013] The parameters for calculating the sliding torque also include: The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle;

[0014] Among them, the slope angle α and the distance to the river b are used to quantitatively calculate the degree of unevenness of the soil outside the narrow foundation pit near the river, and the calculation formulas are as follows:

[0015] Distance from Linhe Upper load The sliding moment generated by the self-weight of the CAPOD region of the upper soil:

[0016] ;

[0017] The sliding moment generated by the self-weight of the soil in the DEKO region of the circular sliding segment:

[0018] ;

[0019] in The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle; and δ is the angle between the center of the circle in the model and the lower soil layer.

[0020] The calculation of the anti-sliding moment needs to consider the shear strength of the sliding surface and the passive earth pressure. Specifically, in the model of a narrow, river-adjacent foundation pit, the influencing factors on the anti-sliding moment for each surface segment are as follows:

[0021] The anti-slip moment MR1 generated by the slope segment AC on the circular arc sliding surface is introduced into the shear strength τ1 of the slope segment AC. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle;

[0022] The anti-slip moment MR2 generated by the straight section CD of the foundation pit on the circular arc sliding surface is introduced into the shear strength τ2 of the straight section CD of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle;

[0023] The anti-slip moment MR3 generated by the arc section DEF of the foundation pit on the arc sliding surface is introduced into the shear strength τ3 of the arc section DEF of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle;

[0024] The anti-slip moment MR4 generated by the circular arc section FG of the foundation pit on the circular arc sliding surface is introduced into the shear strength τ4 of the circular arc section FG of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0025] Among them, the degree of unevenness of the soil outside the narrow foundation pit near the river is quantitatively calculated by using the slope angle α and the distance b from the river. The calculation formulas for the anti-sliding moment MR1 generated by the slope section AC on the circular sliding surface and the anti-sliding moment MR2 generated by the straight section CD of the foundation pit on the circular sliding surface are as follows:

[0026] The anti-slip moment MR1 generated by the slope section AC in the upper slope on the circular arc sliding surface is:

[0027] ;

[0028] ;

[0029] ;

[0030] The anti-slip moment generated by the straight section CD of the foundation pit for circular sliding is:

[0031] ;

[0032] ;

[0033] Where τ1 is the shear strength of slope section AC, and τ2 is the shear strength of straight section CD of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0034] Among them, based on the blocking effect on the lateral soil and support structure when the narrow foundation pit slides and heaves, the anti-sliding moment MR3 generated by the circular arc section DEF of the foundation pit on the circular arc sliding is obtained, and the anti-sliding moment MR4 generated by the circular arc section FG of the foundation pit on the circular arc sliding is calculated as follows:

[0035] The anti-slip moment generated by DEF in the circular arc region of the foundation pit due to the circular arc sliding:

[0036] ;

[0037] The anti-slip moment generated by the circular arc section FG of the foundation pit on the circular arc sliding:

[0038] ;

[0039] in This is the passive earth pressure coefficient;

[0040] The shear strength τ3 of the arc section DEF in the foundation pit and the shear strength τ4 of the arc section FG in the foundation pit are specified. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0041] The study employs two parameters—the force exerted on the foundation pit by river level fluctuations and the seepage force—to numerically calculate the impact of an external river on a narrow, river-adjacent foundation pit. This allows for the calculation of the sliding moment in the river-affected area. The circular sliding surface intersects the riverbank at point C, and the river level is [missing information - likely a specific height or value]. From this, we can deduce the extent of the river's influence on the riverbank:

[0042] ;

[0043] Forces exerted by a river on its banks:

[0044] ;

[0045] The force exerted by the riverbank is F. W ρ is the density of the river water, and g is the acceleration due to gravity.

[0046] Among them, the force of the river on the riverbank Sliding torque:

[0047] ;

[0048] River seepage force on foundation pit Sliding torque:

[0049] ;

[0050] in, It is water-weighted.

[0051] The formula for calculating the heave stability coefficient of narrow foundation pits near rivers is as follows:

[0052] The expression for the total anti-slip moment MR is:

[0053] ;

[0054] The expression for the total sliding torque MS is:

[0055] ;

[0056] Therefore, the heave stability coefficient of a narrow, river-adjacent foundation pit is obtained as follows:

[0057] .

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1. The slope angle of the upper part of the soil outside the pit and the distance to the river are two parameters that reflect the problem of uneven terrain of the soil outside the pit when calculating narrow foundation pits near the river, which makes up for the deficiency of traditional calculation methods that do not take into account the terrain factors outside the pit.

[0060] 2. The two parameters of force and seepage force exerted on the foundation pit by river level changes are used to reflect the impact of rivers outside the pit on the calculation of narrow foundation pits near rivers. Compared with traditional calculation methods, this method has the advantage of considering the influence of rivers outside the pit.

[0061] 3. The slope angle of the upper soil mass outside the pit and the distance to the river are two parameters to reflect the uneven terrain of the soil outside the pit in the calculation of narrow foundation pits near rivers, and to make up for the deficiency of traditional calculation methods that do not consider the terrain factors outside the pit. Among them, the parameters of the force and seepage force exerted on the foundation pit by the river water level change are to reflect the influence of the river outside the pit on the calculation of narrow foundation pits near rivers, which has the advantage of considering the influence of the river outside the pit compared with traditional calculation methods. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the calculation method for the heave stability of a narrow foundation pit near a river according to the present invention.

[0063] Figure 2 A schematic diagram of four parameters is introduced to illustrate the method for calculating the heave stability of a narrow river-adjacent foundation pit according to the present invention.

[0064] Figure 3 This is a schematic diagram of a model for calculating the heave stability of a narrow, river-adjacent foundation pit according to the present invention.

[0065] Figure 4 This is a schematic diagram simulating a narrow riverside foundation pit according to the present invention.

[0066] Figure 5 This is a comparative verification diagram of the method for calculating the heave stability of a narrow river-side foundation pit according to the present invention. Detailed Implementation

[0067] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0068] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the river-adjacent section AC is a slope. Considering the influence of the upper terrain, the anti-sliding moment is determined using the limit equilibrium analysis method. This moment is composed of the shear strength of the slope section AC, the shear strength of the straight section CD of the foundation pit, the shear strength of the circular section DEFG of the foundation pit, the passive earth pressure of the straight section GJ, and the ultimate resisting bending moment provided by the wall. Provided jointly. Since the ultimate bending moment resistance of underground walls is difficult to determine due to variations in material structure and thickness, this invention disregards this factor as a safety margin. The sliding moment is mainly determined by the force acting at the distance from the river. Upper load The sliding moment is provided by the self-weight of the upper soil CAPOD region and the self-weight of the soil DEKO region in the circular sliding segment. The self-weight of the soil in region KEF cancels out the self-weight of the soil in region KFG, and its sliding moment is not calculated.

[0069] Step 1: Establish a model of a narrow, river-adjacent foundation pit, including the slope section AC, the straight section CD, the circular section DEF, the circular section FG, the straight section GJ, the upper load q, the upper soil CAPOD region, and the circular sliding section DEKO region; the intersection point C of the circular sliding surface of the upper soil CAPOD region with the riverbank slope, and the river water level at a height h above the ground. w ,

[0070] Among them, when the pile length L ≤ the pit width B, it is defined as a narrow pit;

[0071] When the pile length L > the pit width B, it is defined as a general type of pit.

[0072] Among them, the circular sliding radius of the narrow foundation pit is R=B, the center O is located at the lower part of the intersection of the pit bottom and the support structure, and the buried depth is O=H+LR, where H is the excavation depth of the foundation pit and L is the pile length;

[0073] Step 2: Based on the established model, considering the obstruction effect of circular arc sliding heave on the lateral soil and support structure during narrow foundation pit heave, and taking into account topographic factors, the following parameters are introduced as calculation parameters for the stability analysis method of river-adjacent narrow foundation pit heave: slope angle α, distance from the river b, and the force F generated by river water level fluctuations on the foundation pit. w The seepage force generated by changes in river water level on the foundation pit;

[0074] Step 3: Based on the model from Step 1 and the parameters from Step 2, calculate the anti-sliding moment MR1 generated by slope segment AC on the circular sliding surface; calculate the anti-sliding moment MR2 generated by the straight section CD of the foundation pit on the circular sliding surface; calculate the anti-sliding moment MR3 generated by the circular sliding surface DEF of the foundation pit on the circular sliding surface; calculate the anti-sliding moment MR4 generated by the circular sliding surface FG of the foundation pit on the circular sliding surface; calculate the sliding moment MS1 generated by the upper load q at the distance b from the river and the self-weight of the upper soil CAPOD region; calculate the sliding moment MS2 generated by the self-weight of the soil DEKO region of the circular sliding segment; and calculate the riverbank force F. W Sliding torque MSW F The sliding moment MSW of the river on the seepage force J of the foundation pit f ;

[0075] Step 4: Based on the parameters MR1, MR2, MR3, MR4, MS1, MS2, and MSW calculated in Step 3... F and MSW fThe total anti-sliding moment MR and the total sliding moment MS were calculated, and finally the heave stability coefficient k of the narrow excavation pit near the river was obtained. s .

[0076] The calculation of the anti-sliding moment needs to consider the shear strength of the sliding surface and the passive earth pressure. Specifically, in the model of a narrow foundation pit near a river, the influencing factors of the anti-sliding moment for each surface segment are as follows:

[0077] The anti-slip moment MR1 generated by the slope segment AC on the circular sliding surface needs to be considered in the formula, taking into account the shear strength τ1 of the slope segment AC. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0078] The anti-slip moment MR2 generated by the straight section CD of the foundation pit on the circular arc sliding surface needs to be considered in the formula, taking into account the shear strength τ2 of the straight section CD of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0079] The anti-slip moment MR3 generated by the arc section DEF of the foundation pit on the arc sliding surface needs to be considered in the formula, taking into account the shear strength τ3 of the arc section DEF of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0080] The anti-slip moment MR4 generated by the circular arc section FG of the foundation pit on the circular arc sliding surface needs to be considered in the formula, taking into account the shear strength τ4 of the circular arc section FG of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0081] The slope angle α and the distance to the river b are used to quantitatively calculate the degree of unevenness of the soil outside the narrow foundation pit near the river. The formulas for calculating the anti-sliding moment MR1 generated by the slope section AC on the circular sliding surface and the anti-sliding moment MR2 generated by the straight section CD of the foundation pit on the circular sliding surface are as follows:

[0082] The anti-slip moment MR1 generated by the slope section AC in the upper slope on the circular arc sliding surface is:

[0083] ;

[0084] ;

[0085] ;

[0086] The anti-slip moment generated by the straight section CD of the foundation pit for circular sliding is:

[0087] ;

[0088] ;

[0089] Where τ1 is the shear strength of slope section AC, and τ2 is the shear strength of straight section CD of the foundation pit. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0090] Among them, based on the blocking effect on the lateral soil and support structure when the narrow foundation pit slides and heaves, the anti-sliding moment MR3 generated by the circular arc section DEF of the foundation pit on the circular arc sliding is obtained, and the anti-sliding moment MR4 generated by the circular arc section FG of the foundation pit on the circular arc sliding is calculated as follows:

[0091] The anti-slip moment generated by DEF in the circular arc region of the foundation pit due to the circular arc sliding:

[0092] ;

[0093] The anti-slip moment generated by the circular arc section FG of the foundation pit on the circular arc sliding:

[0094] ;

[0095] in This is the passive earth pressure coefficient;

[0096] The shear strength τ3 of the arc section DEF in the foundation pit and the shear strength τ4 of the arc section FG in the foundation pit are specified. The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0097] The sliding moment is mainly provided by the upper load q acting at the distance b from the river, the self-weight of the upper soil CAPOD region, and the self-weight of the soil DEKO region of the circular sliding section.

[0098] The slope angle α and the distance to the river b can be used to quantitatively calculate the degree of unevenness of the soil outside the narrow foundation pit near the river.

[0099] The remaining calculation parameters for the sliding torque include: The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0100] The slope angle α and the distance to the river b are used to quantitatively calculate the degree of unevenness of the soil outside the narrow foundation pit near the river. The calculation formulas for the sliding moment MS1 caused by the self-weight of the upper soil CAPOD region and the sliding moment MS2 caused by the self-weight of the soil DEKO region in the circular sliding section are as follows:

[0101] Distance from Linhe Upper load The sliding moment generated by the self-weight of the CAPOD region of the upper soil:

[0102] ;

[0103] The sliding moment generated by the self-weight of the soil in the DEKO region of the circular sliding segment:

[0104] ;

[0105] in The soil weight; This is the distance between the contact point between the slip surface and the slope surface and the top of the slope; Distance to the river; Upper load; This is the active earth pressure coefficient; For effective internal cohesion; α is the effective internal friction angle; α is the slope angle.

[0106] The study uses two parameters—the force exerted on the foundation pit by river level fluctuations and the seepage force—to numerically calculate the impact of a river on a narrow, river-adjacent foundation pit. This allows for the calculation of the sliding moment in the river-affected area. The circular sliding surface intersects the riverbank at point C, and the river level is [missing information - likely a height measurement]. From this, we can deduce the extent of the river's influence on the riverbank:

[0107] ;

[0108] Forces exerted by a river on its banks:

[0109] ;

[0110] Among them, the force F of the riverbank W .

[0111] Among them, the force of the river on the riverbank Sliding torque:

[0112] ;

[0113] River seepage force on foundation pit Sliding torque:

[0114] ;

[0115] in, It is water-weighted.

[0116] In summary, the formula for calculating the heave stability coefficient of a narrow excavation pit near a river is as follows:

[0117] The expression for the total anti-slip moment MR is:

[0118] ;

[0119] The expression for the total sliding torque MS is:

[0120] ;

[0121] Therefore, the heave stability coefficient of a narrow, river-adjacent foundation pit is obtained as follows:

[0122] . Specific Implementation

[0123] The design conditions are: a foundation pit depth of 7m, an excavation width of 8m, an insertion depth of 9m, a soil unit weight of 18kN / m³, a water unit weight of 10kN / m³, a soil cohesion of 10kPa, an internal friction angle of 20°, a river distance of 4m, a slope angle of 45°, and a foundation pit width of 8m. The water level difference (i.e., the difference between ground elevation and water surface elevation) is incorporated into the calculations. The results of calculations using the method provided in this invention and the standard method are compared as follows: Figure 5 As shown. From Figure 5 As can be seen from this, the method in this paper obtains k s All values ​​are greater than the standard values. Therefore, in practical engineering, the heave stability coefficient of narrow river-side foundation pits calculated using this method is higher than that calculated using the traditional standard method, indicating better stability for such pits. With better stability, the actual pile length driven into the foundation pit can be shortened, which is beneficial for saving engineering costs.

[0124] The present invention has the following advantages:

[0125] 1. The slope angle of the upper part of the soil outside the pit and the distance to the river are two parameters that reflect the problem of uneven terrain of the soil outside the pit when calculating narrow foundation pits near the river, which makes up for the deficiency of traditional calculation methods that do not take into account the terrain factors outside the pit.

[0126] 2. The two parameters of force and seepage force exerted on the foundation pit by river level changes are used to reflect the impact of rivers outside the pit on the calculation of narrow foundation pits near rivers. Compared with traditional calculation methods, this method has the advantage of considering the influence of rivers outside the pit.

[0127] 3. This method is applicable to narrow foundation pit projects constructed near rivers and along riverbanks. By considering the obstruction effect of the soil and support structure on the opposite side of the narrow foundation pit, it introduces four parameters: topographic factors such as slope angle and distance from the river, as well as the force and seepage force generated by river water level changes on the foundation pit. The calculation formula can be used to calculate the heave stability of narrow foundation pits near inland rivers, achieving the application goal of safe calculation and design, conforming to actual conditions, and saving economy. It solves the problem of discrepancies between the results and reality and economic waste caused by current design calculations.

[0128] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for calculating and analyzing uplift stability of a narrow foundation pit adjacent to a river, characterized in that, The method comprises the following steps: Step 1: Establish a model of a river-side narrow foundation pit, including a slope section AC, a straight foundation pit section CD, a circular arc foundation pit section DEF, a circular arc foundation pit section FG, a straight foundation pit section GJ, an upper load q, an upper soil CAPOD area, and a circular arc sliding section DEKO area; the intersection point C of the circular arc sliding surface of the upper soil CAPOD area and the river bank, and the height of the river water level from the ground is h w , Wherein, when the pile length L≤width of foundation pit B, it is defined as narrow type foundation pit; Wherein, the radius of the circular arc sliding of the narrow type foundation pit is R=B, the center of the circle O is located at the lower part of the intersection of the pit bottom and the supporting structure, and the position of the buried depth is O=H+L-R, wherein H is the excavation depth of the foundation pit, and L is the pile length; Step 2: On the basis of the model, the following parameters are introduced as the calculation parameters of the anti-heave stability calculation and analysis method of the river-adjacent type narrow foundation pit, including: slope angle a, river-adjacent distance b, force F generated by river water level fluctuation on the foundation pit w , and penetration force J generated by river water level fluctuation on the foundation pit; Step 3: According to the model of step 1 and the parameters of step 2, calculate the anti-sliding moment MR1 generated by the slope section AC on the circular sliding surface, calculate the anti-sliding moment MR2 generated by the straight line area section CD on the circular sliding surface, calculate the anti-sliding moment MR3 generated by the circular arc area section DEF on the circular sliding surface, calculate the anti-sliding moment MR4 generated by the circular arc area section FG on the circular sliding surface, calculate the sliding moment MS1 generated by the upper load q on the distance b from the river and the self-weight of the upper soil CAPOD area, calculate the sliding moment MS2 generated by the self-weight of the soil DEKO area on the circular sliding section, calculate the sliding moment MSW of the river bank force F W F , the sliding moment MSW of the river seepage force J on the foundation pit f ;​ Step 4: According to the parameters MR1, MR2, MR3, MR4, MS1, MS2, MSW calculated in step 3 F and MSW f , the total anti-sliding moment MR and the total sliding moment MS are calculated, and finally the anti-heave stability coefficient k of the river-side narrow foundation pit is obtained s ; Wherein, the sliding torque is mainly provided by the upper load q acting on the river distance b, the self weight of the upper soil CAPOD region, and the self weight of the circular arc sliding section soil DEKO region; Wherein, the slope angle a and the river distance b can be used to quantitatively calculate the degree of unevenness of the soil terrain outside the river type narrow foundation pit; The sliding moment calculation parameters further include: is the bulk density of the soil; is the distance from the contact point of the sliding surface and the slope to the top of the slope; is the distance from the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and is the slope angle. Wherein, the slope angle a and the river distance b are used to quantitatively calculate the degree of unevenness of the soil terrain outside the river type narrow foundation pit, and the calculation formulas of the sliding torque MS1 generated by the self weight of the upper soil CAPOD region and the sliding torque MS2 generated by the self weight of the circular arc sliding section soil DEKO region are respectively: The upper load on the distance from the river The sliding moment generated by the self-weight of the upper soil body CAPOD region: ； The sliding torque generated by the self weight of the circular arc sliding section soil DEKO region: ； wherein γ is the unit weight of the soil; L is the distance from the contact point of the slip surface and the slope surface to the top of the slope; D is the distance from the river; W is the upper load; K is the active earth pressure coefficient; C is the effective internal cohesion; φ is the effective internal friction angle; and α is the slope angle, and δ is the angle between the center of the model and the lower soil layer.

2. The river type narrow foundation pit anti-heave stability calculation and analysis method according to claim 1, characterized in that, The calculation of the anti-sliding torque needs to consider the shear strength of the sliding surface involved and the passive earth pressure; wherein the influencing factors of the anti-sliding torque of each surface section in the model of the river type narrow foundation pit are as follows: Where the anti-sliding moment MR1 generated by the slope section AC to the circular arc sliding surface is introduced into the shear strength τ1 of the slope section AC, is the soil bulk density; is the distance between the contact point of the sliding surface and the slope and the slope top; is the distance to the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and α is the slope angle. wherein the anti-sliding moment MR2 generated by the straight area segment CD of the foundation pit on the circular arc sliding surface is introduced into the shear strength τ2 of the straight area segment CD of the foundation pit, is the bulk density of the soil; is the distance between the contact point of the sliding surface and the slope and the top of the slope; is the distance from the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and α is the slope angle. Wherein the anti-sliding moment MR3 generated by the foundation pit circular arc area segment DEF to the circular arc sliding surface, the shear strength τ3 of the foundation pit circular arc area segment DEF is introduced, is the soil bulk density; is the distance between the contact point of the sliding surface and the slope and the top of the slope; is the distance from the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and α is the slope angle. Wherein the foundation pit circular arc region segment FG produces the anti-sliding moment MR4 to the circular arc sliding surface, the shear strength τ4 of the foundation pit circular arc region segment FG is introduced, The bulk density of the soil; The distance between the contact point of the sliding surface and the slope top and the slope top; The distance from the river; The upper load; The active earth pressure coefficient; The effective internal cohesion; The effective internal friction angle; and α is the slope angle.

3. The river type narrow foundation pit anti-heave stability calculation and analysis method according to claim 2, characterized in that, The slope angle a and the river distance b are used to quantitatively calculate the degree of unevenness of the soil terrain outside the river type narrow foundation pit, and the calculation formulas of the anti-sliding torque MR1 generated by the slope section AC on the circular arc sliding surface and the anti-sliding torque MR2 generated by the straight line region section CD on the circular arc sliding are respectively: Wherein, the anti-sliding torque MR1 generated by the slope section AC on the circular arc sliding surface in the upper slope is: ； ； ； Wherein, the anti-sliding torque MR2 generated by the straight line region section CD on the circular arc sliding is: ； ； where τ1 is the shear strength of the slope segment AC, τ2 is the shear strength of the straight segment CD of the foundation pit, is the bulk density of the soil; is the distance from the contact point of the sliding surface and the slope to the top of the slope; is the distance from the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and α is the slope angle.

4. The river type narrow foundation pit anti-heave stability calculation and analysis method according to claim 2, characterized in that, According to the blocking effect of the narrow foundation pit circular arc sliding heave on the side soil and the supporting structure, the calculation formulas of the anti-sliding torque MR3 generated by the foundation pit circular arc region section DEF on the circular arc sliding and the anti-sliding torque MR4 generated by the foundation pit circular arc region section FG on the circular arc sliding are: Wherein, the anti-sliding torque MR3 generated by the foundation pit circular arc region section DEF on the circular arc sliding is: ； Wherein, the anti-sliding torque MR4 generated by the foundation pit circular arc region section FG on the circular arc sliding is: ； wherein Kp is the passive earth pressure coefficient; Wherein the foundation pit circular arc region section DEF shear strength τ3, foundation pit circular arc region section FG shear strength τ4, is the soil bulk density; is the distance between the contact point of the sliding surface and the slope and the top of the slope; is the distance from the river; is the upper load; is the active earth pressure coefficient; is the effective internal cohesion; is the effective internal friction angle; and α is the slope angle.

5. The river type narrow foundation pit anti-heave stability calculation and analysis method according to claim 1, characterized in that, The numerical calculation of the influence of river on the narrow foundation pit is carried out by using the two parameters of the force and the seepage force of the river level variation on the foundation pit, and then the sliding torque calculation of the area affected by the river is completed. The intersection C exists between the circular arc sliding surface and the river bank slope, and the height of the river level from the ground is Therefore, the range of the river on the river bank is obtained. ； The force of the river on the river bank: ； where F is the bank force W , p is the density of the river water, and g is the acceleration of gravity.

6. The river type narrow foundation pit anti-heave stability calculation and analysis method according to claim 5, characterized in that, River force on bank Moment of sliding force: ； River to the foundation pit permeability of sliding moment: ； wherein is the water density.

7. The method for calculating and analyzing the uplift stability of a narrow foundation pit adjacent to a river according to any one of claims 1 to 6, characterized in that, Wherein, the calculation formula of the river type narrow foundation pit anti-heave stability coefficient is as follows: The expression of the total anti-sliding torque MR is: ； The expression of the total sliding torque MS is: ； Therefore, the river type narrow foundation pit anti-heave stability coefficient is: 。

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