Internal force and displacement analysis method of double-row steel sheet pile support structure

Abstract

The invention discloses an internal force and displacement analysis method for a double-row steel sheet pile supporting structure. The method calculates the initial forces of the front-row piles and the rear-row piles according to the relative position relationship between the rear-row piles and the active earth pressure fracture surface. The method also iterates and calculates the final displacement and corresponding internal force of the double-row steel sheet piles under the condition that the displacements of the pile tops of the front-row piles and the front-row piles are equal by ignoring the tensile elongation of the tension rod. The method thus determines whether the design parameters of the supporting structure are safe and reasonable, whether the modeling process complies with the force law, and whether the final state is convergent, stable, and in line with the actual engineering practice. The method has negligible limitations for solving engineering technical problems.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and in particular to an internal force and displacement analysis method for a double-row steel sheet pile support structure. Background Art

[0002] The steel sheet pile support structure has the advantages of reliable quality, fast construction speed and low cost, but the rigidity of a single row of steel sheet piles is relatively small, and the applicable geological conditions and foundation pit depth are limited. It often needs to be supplemented with anchor rods or internal supports to play a greater role. In order to increase the support capacity of a single row of steel sheet piles, a double row of steel sheet pile support structure has appeared in recent years, that is, a row of steel sheet piles is constructed on the side of the single row of steel sheet piles away from the foundation pit, and the two rows of steel sheet piles are connected by tie rods to play a role in jointly resisting soil pressure.

[0003] Double-row steel sheet piles have a higher support capacity, so they can be used in worse geological conditions and deeper foundation pits without internal support, and their application scenarios have been further expanded. In engineering practice, finite element algorithms can be used for this relatively new support structure, but finite element algorithms are relatively complex and the criteria for judging the calculation results are unclear. It is currently in the stage of accumulating experience.

[0004] The national standard "Technical Code for Building Foundation Pit Support" JGJ120-2012 and the local standard Guangdong Provincial Standard "Technical Code for Building Foundation Pit" DBJ / T15-20-2016 proposed a double-row bored pile calculation model, but the model has some defects: (1) No matter how far the rear row of piles is from the front row of piles, they are subject to the same active earth pressure, but in reality, the farther the rear row of piles is from the foundation pit, the smaller the active earth pressure they are subject to; (2) The force exerted by the soil between the front and rear rows of piles on the piles is theoretically the internal force of the structural system that achieves self-balance through the connecting beam, and should not be calculated as an external force of the structural system. Through trial calculations, the calculated displacement of this model when applied to double-row steel sheet piles is obviously too large, and the displacement size is significantly affected by the stiffness of the cap beam and the connecting beam.

[0005] In response to the above problems, the Guangdong Provincial Standards and Regulations also proposed in the appendix that the active earth pressure is distributed by the front and rear rows of piles through the distribution coefficient. The distribution coefficient adopts the relevant assumptions of the limit equilibrium method in traditional classical soil mechanics when deriving it. It has certain logical rationality, but it has not been verified. Another method is to regard the double-row piles as a rigid portal frame, reduce the portal frame stiffness and calculate it according to the single-row pile, but there is no basis for the reduction coefficient. Summary of the invention

[0006] In view of the current lack of mature force distribution calculation method for double-row steel sheet pile support structure, the present invention proposes an internal force and displacement analysis method for double-row steel sheet pile support structure, which mainly solves the problems of background technology.

[0007] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0008] A method for analyzing internal forces and displacements of a double-row steel sheet pile support structure comprises the following steps:

[0009] The double-row steel sheet piles include the front row piles and the rear row piles. The tops of the two piles are connected by tie rods. The tensile elongation of the tie rods is ignored. According to the relative position relationship between the rear row piles and the active earth pressure rupture surface, the modified earth pressure at the bottom of the front row pile foundation pit and the active earth pressure resultant of the rear row piles are calculated respectively.

[0010] The front row of piles is regarded as a single row of piles, a tension force is set, and the distributed modified earth pressure is applied to the front row of piles to calculate the displacement of the top of the front row of piles;

[0011] The rear row piles are regarded as ordinary piles that are cantilevered above the intersection of the fracture surfaces, the tension rod force acts on the pile top, and the distributed active earth pressure resultant force acts on the rear row piles to calculate the displacement of the rear row pile tops;

[0012] Ignoring the influence of the tension rod deformation, the tension rod force is adjusted through repeated iterations until the displacement of the top of the front row piles is equal to the displacement of the top of the rear row piles. The iteration is terminated and the top displacement of the double row of steel sheet piles and the corresponding internal force state are output.

[0013] In some embodiments, the calculation method of the modified earth pressure is:

[0014] q'2=2(Ea 总 -Ea 后 ) / (h1+h2);

[0015] In the formula, Ea 总 is the active earth pressure force on the double-row steel sheet piles, Ea 后 is the resultant of active earth pressure on the rear row piles, h1 is the height from the bottom of the foundation pit to the intersection of the rupture surface and the rear row piles; h2 is the height from the ground to the intersection of the rupture surface and the rear row piles.

[0016] In some embodiments, the calculation method of the displacement of the top of the front row of piles is:

[0017]

[0018] Where x0 is the horizontal displacement at the bottom of the front row of pile foundation pit, is the rotation angle at the bottom of the foundation pit of the front row piles, h1 is the height from the bottom of the foundation pit to the intersection of the fracture surface and the rear row piles, h2 is the height from the ground to the intersection of the fracture surface and the rear row piles, Δ 前0 It is the displacement of the pile top caused by the elastic deflection of the front row of piles above the pit bottom.

[0019] In some embodiments, the calculation method of the displacement of the top of the rear row piles is:

[0020]

[0021] Where x0 is the horizontal displacement at the bottom of the front row of pile foundation pit, is the rotation angle at the bottom of the front row pile foundation pit, h2 is the height from the ground to the intersection of the fracture surface and the rear row pile, Δ 后0 It is the displacement of the pile top caused by the elastic deflection of the rear row of piles above the pit bottom.

[0022] In some embodiments, the pile top displacement of the double-row steel sheet piles is:

[0023] Δ=γΔ 前 or γΔ 后 ;

[0024] In the formula, γ is the correction coefficient, Δ 前 is the displacement of the top of the front row piles, Δ 后 is the displacement of the top of the rear row of piles.

[0025] The beneficial effects of the present invention are as follows: the initial forces of the front row piles and the rear row piles are calculated through the relative position relationship between the rear row piles and the active earth pressure rupture surface, and the final displacements and corresponding internal forces of the double row steel sheet piles are iteratively calculated by ignoring the tensile elongation of the tie rod and the condition that the displacements of the tops of the front and rear row piles are equal, so as to judge whether the design parameters of the support structure are safe and reasonable, the modeling process conforms to the force law, and the final state is convergent, stable, and conforms to the actual engineering situation. For solving engineering technical problems, its limitations can be ignored. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic flow chart of an internal force and displacement analysis method for a double-row steel sheet pile support structure disclosed in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a double-row steel sheet pile model disclosed in an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the force analysis of the front row piles disclosed in an embodiment of the present invention;

[0029] Figure 4 A schematic diagram of force analysis of the rear row piles disclosed in an embodiment of the present invention;

[0030] Figure 5 It is a schematic diagram of the deformation of a pile at the bottom surface of a foundation pit when a unit shear force acts on the bottom surface of a foundation pit according to an embodiment of the present invention;

[0031] Figure 6 It is a schematic diagram of the deformation of a pile at the bottom surface of a foundation pit when a unit bending moment acts on the bottom surface of a foundation pit according to an embodiment of the present invention;

[0032] Figure 7It is a schematic diagram of displacement calculation of double-row steel sheet piles disclosed in a specific example;

[0033] Figure 8 A schematic diagram of the calculation of the displacement of the top of the front row piles disclosed in a specific example;

[0034] Fig. 9 It is a schematic diagram of the displacement calculation of the top of the rear row piles disclosed in a specific example;

[0035] Fig.10 This is a schematic diagram of the calculation parameter settings of Lizheng Deep Foundation Pit 7.0BP5 software;

[0036] Fig.11 This is a schematic diagram of the displacement calculation results of the Lizheng deep foundation pit 7.0BP5 software;

[0037] Fig.12 This is a schematic diagram of the displacement data monitored on site. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the content of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the contents.

[0039] This embodiment proposes a method for analyzing the internal force and displacement of a double-row steel sheet pile support structure. Figure 1 As shown, the following steps S1-S4 are included:

[0040] S1, double-row steel sheet piles include front row piles and rear row piles. The tops of the two piles are connected by tie rods. The tensile elongation of the tie rods is ignored. According to the relative position relationship between the rear row piles and the active earth pressure rupture surface, the corrected earth pressure at the bottom of the front row pile foundation pit and the active earth pressure resultant of the rear row piles are calculated respectively.

[0041] In the double-row steel sheet pile support structure described in this embodiment, the pile tops of the front and rear rows of piles are connected by tie rods. It is assumed that the tie rods are not deformed, that is, the displacements of the front and rear rows of piles at the pile tops are equal, and the tie rods and steel sheet piles are hinged. The calculation model is as follows: Figure 2 shown.

[0042] The active earth pressure on the double-row steel sheet piles is related to the spacing between the rows of piles. When the distance between the rear row of piles and the front row of piles is zero, the active earth pressure acts on the rear row of piles first; when the rear row of piles is far away from the front row of piles and outside the range of the active earth pressure rupture surface, the active earth pressure on the rear row of piles is zero; when the rear row of piles is within the range of the active earth pressure rupture surface, the front row of piles bears the active earth pressure below the intersection of the rear row of piles and the rupture surface, such as Figure 3-4As shown in the figure, the front row piles are subjected to the soil pressure below the intersection of the active soil pressure rupture surface and the rear row piles, and the rear row piles are subjected to the active soil pressure above the intersection of the active soil pressure rupture surface and themselves. The soil pressures on the front and rear row piles are both triangularly distributed. The front and rear row piles eventually reach their final stress and deformation states under the coordination of the tie rods. The effects are shown in the figure below. Figure 5-6 shown.

[0043] Figure 3-6 In: W is the spacing between the double rows of piles, h is the embedding depth of the front row of piles, h+h1 is the embedding depth of the rear row of piles, h1 is the height from the bottom of the foundation pit to the intersection of the fracture surface and the rear row of piles, h2 is the height from the ground to the intersection of the fracture surface and the rear row of piles, L is the length of the steel sheet pile, is the internal friction angle of the soil, H is the tension of the tie rod, q1 is the active earth pressure at a depth of h2 below the ground; q'2 is the modified earth pressure at the bottom of the foundation pit, Ea 前 is the resultant earth pressure on the front row of piles, Ea 后 is the active earth pressure force on the rear row of piles, Δ 前 is the displacement of the top of the front row of piles, Δ 后 is the displacement of the top of the rear row of piles, x0 is the horizontal displacement of the steel sheet pile at the bottom of the foundation pit, The corner of the steel sheet pile at the bottom of the foundation pit.

[0044] First, after the foundation pit is excavated to the bottom of the pit, the front row of piles are subjected to the soil pressure below the intersection of the active soil pressure rupture surface and the rear row of piles, as well as the force of the pull rod. The pile top displacement and the internal force and displacement of the pile body can be calculated using the m method or other suitable theoretical methods. In the example of the present invention, the m method is used to calculate the horizontal displacement of the pile top of the front row of piles. The m method is a method used to calculate the horizontal displacement and action effect of elastic piles, which was first proposed by Matlock and Reese in 1956. Compared with other methods such as the constant method and the parabola method, the m method has its unique application scenarios and advantages.

[0045] The soil pressure is triangularly distributed, and the modified soil pressure q'2 at the bottom of the front row pile foundation pit can be calculated based on the distribution form, as shown in the following S101-S103.

[0046] S101, calculate the active earth pressure resultant of double-row steel sheet piles:

[0047]

[0048] In the formula, Ea 总 is the resultant active earth pressure on the double-row steel sheet piles, h1 is the height from the bottom of the foundation pit to the intersection of the rupture surface and the rear row of piles; h2 is the height from the ground to the intersection of the rupture surface and the rear row of piles, and q2 is the active earth pressure at a depth of h1+h2 below the ground.

[0049] S102, calculate the active earth pressure resultant of the rear row of piles:

[0050]

[0051] In the formula, Ea 后 is the active earth pressure on the rear row of piles, h2 is the height from the ground to the intersection of the rupture surface and the rear row of piles, and q1 is the active earth pressure at a depth of h1 below the ground.

[0052] S103, according to equations (1) and (2), the calculation method of the modified earth pressure is:

[0053] q'2=2(Ea 总 -Ea 后 ) / (h1+h2) (3);

[0054] In the formula, Ea 总 is the active earth pressure force on the double-row steel sheet piles, Ea 后 is the resultant of active earth pressure on the rear row piles, h1 is the height from the bottom of the foundation pit to the intersection of the rupture surface and the rear row piles; h2 is the height from the ground to the intersection of the rupture surface and the rear row piles.

[0055] S2, regard the front row of piles as a single row of piles, set a tension force, and act on the front row of piles with the distributed modified earth pressure, and calculate the displacement of the top of the front row of piles.

[0056] In this embodiment, the horizontal displacement of the top of the front row of piles is calculated according to Appendix L of the "Code for Design of Highway Bridge and Culvert Foundations and Substructures". See S201-S206 below for details.

[0057] S201, determine the deformation coefficient of the front row of piles:

[0058]

[0059] In the formula, α is the deformation coefficient of the pile (1 / m); m is the proportional coefficient of the horizontal resistance coefficient of the non-rock foundation, which is determined by experiments. When there is a lack of test data, it can be checked according to Table L.0.2-1 of the "Code for Design of Highway Bridge and Culvert Foundations" based on the classification and state of the soil; b1 is the calculated width of the steel sheet pile; EI is the bending stiffness of the pile.

[0060] S202, requirements for the embedding depth of the front row piles:

[0061] αh>2.5(5);

[0062] Where h is the embedment depth of the pile.

[0063] S203, the effect of the front row of piles at the bottom of the foundation pit:

[0064]

[0065] Where M0 is the bending moment of the steel sheet pile at the bottom of the foundation pit; H0 is the shear force of the steel sheet pile at the bottom of the foundation pit; h1 is the height from the bottom of the foundation pit to the intersection of the rupture surface and the rear row of piles; h2 is the height from the ground to the intersection of the rupture surface and the rear row of piles; q'2 is the corrected earth pressure at the bottom of the foundation pit; H is the tension of the tie rod, which is positive toward the foundation pit side.

[0066] S204, displacement of the section when a unit force acts on the bottom of the foundation pit:

[0067] When H0=1:

[0068] Horizontal displacement

[0069] Angle (rad)

[0070] When M0=1:

[0071] Horizontal displacement

[0072] Angle (rad)

[0073] Where: coefficient A i , B i , C i , D i (i=1、2、3、4) values, in calculation When, according to Refer to Table L.0.8 of the Code for Design of Highway Bridge and Culvert Foundations; When calculate; Physical meaning Figure 4 , Figure 5 ;

[0074] S205, displacement of the front row of piles at the bottom of the foundation pit:

[0075] Horizontal displacement

[0076] Angle (rad)

[0077] S206, the calculation method of the displacement of the top of the front pile is:

[0078]

[0079] Where x0 is the horizontal displacement at the bottom of the front row of pile foundation pit, is the rotation angle at the bottom of the foundation pit of the front row piles, h1 is the height from the bottom of the foundation pit to the intersection of the fracture surface and the rear row piles, h2 is the height from the ground to the intersection of the fracture surface and the rear row piles, Δ 前0It is the displacement of the pile top caused by the elastic deflection of the front row of piles above the pit bottom.

[0080] in,

[0081] S3, the rear row piles are regarded as ordinary piles that are cantilevered above the intersection of the rupture surfaces. The tension force acts on the pile top, and the distributed active earth pressure is applied to the rear row piles to calculate the displacement of the rear row pile tops.

[0082] The top of the rear row pile is located on the ground, and the intersection between the ground and the rupture surface is in a cantilever state. It is subject to the action of the tension rod force and the active earth pressure. The horizontal displacement of the top of the rear row pile is calculated using the m method.

[0083] S301, the effect of the rear piles on the ground:

[0084]

[0085] S302, the deformation coefficient of the rear row of piles, the required embedding depth and the displacement of the cross section caused by the unit force acting on the bottom of the foundation pit. The calculation method refers to equations (4)-(13).

[0086] S303, the calculation method of the displacement of the top of the rear pile is:

[0087]

[0088] Where x0 is the horizontal displacement at the bottom of the front row of pile foundation pit, is the rotation angle at the bottom of the front row pile foundation pit, h2 is the height from the ground to the intersection of the fracture surface and the rear row pile, Δ 后0 It is the displacement of the pile top caused by the elastic deflection of the rear row of piles above the pit bottom.

[0089] in,

[0090] S4, ignoring the influence of the tie rod deformation, adjust the tie rod force through repeated iterations until the displacement of the top of the front row piles is equal to the displacement of the top of the rear row piles, terminate the iteration, and output the top displacement of the double row of steel sheet piles at this time, as well as the corresponding internal force state.

[0091] In this embodiment, due to the particularity of geotechnical engineering, a correction coefficient can be added before the calculated final displacement. The coefficient is determined based on the actual application conditions and local experience of the double-row steel sheet piles. Finally, the pile top displacement of the double-row steel sheet piles is:

[0092] Δ=γΔ 前 or γΔ 后 (20).

[0093] In the formula, γ is the correction coefficient, Δ 前 is the displacement of the top of the front row piles, Δ 后is the displacement of the top of the rear row of piles.

[0094] It should be noted that the above internal force state can also be calculated according to the m method with reference to the above steps S1-S4, and the specific process will not be repeated here.

[0095] The following is a specific example for illustration:

[0096] The foundation pit project of a water plant in Nanzhou, Guangzhou, adopts double-row steel sheet pile cantilever support. The calculation diagram is as follows: Figure 7-9 As shown in the figure, the foundation pit depth is 5m, the spacing between double-row steel sheet piles is 3.5m, the steel sheet pile length is 15m, the steel sheet pile model is Type IV, and the geological conditions are a plain fill layer of 3.1m (γ=18.5kN / m 3 , c = 10 kP, Silt layer 6.4m (γ=16.3kN / m 3 , c = 6kP, Below it is a coarse sand layer (c=0kP, Proportional coefficient of horizontal resistance coefficient of foundation m = 5000kN / m 4 , elastic modulus of steel sheet pile E = 2.05 × 10 8 kPa, section inertia moment I = 3.96 × 10 -4 m 4 , the connecting rod is made of φ32mm steel bar, and the calculated width b1 = 1m. For the convenience of calculation, the weighted average of the plain fill layer and the silt layer is simplified into one soil layer (γ = 17.0kN / m 3 , c=7.31kP, ).

[0097] (1) Calculate the corrected earth pressure at the bottom of the front row pile foundation pit

[0098] Calculation of active earth pressure coefficient K a ,

[0099] The height h1 from the bottom of the foundation pit to the intersection of the fracture surface and the rear row of piles,

[0100] The height from the ground to the intersection of the fracture surface and the rear row of piles is h2, h2 = Lh-h1 = 1.022m

[0101] Calculate the active earth pressure q1,

[0102] Calculate the active earth pressure Ea of the rear piles 后 ,

[0103] Calculate the active earth pressure q2,

[0104] Calculation of active earth pressure Ea of double-row piles 总 ,

[0105] Calculate the corrected earth pressure q'2 at the bottom of the front row pile foundation pit,

[0106] q'2=2(Ea 总 -Ea 后 ) / (h1+h2)=52.476kPa

[0107] (2) Calculate the horizontal displacement of the top of the front row of piles

[0108] According to Appendix L of the "Design Code for Highway Bridge and Culvert Foundations and Subgrades", the horizontal displacement of the top of the front row of piles is calculated. The calculation diagram is as follows Figure 8 shown.

[0109] 1) Deformation coefficient of steel sheet pile:

[0110]

[0111] 2) Requirements for embedding depth of steel sheet piles:

[0112] Front pile: αh=0.573×10=5.727>2.5

[0113] 3) Effect of the front row of piles at the bottom of the foundation pit:

[0114] The tension of the pull rod is temporarily taken as H = -10kN;

[0115] Calculate the shear force H0 of the steel sheet pile at the bottom of the foundation pit, Calculate the bending moment M0 of the steel sheet pile at the bottom of the foundation pit,

[0116]

[0117] 4) The displacement of the section when a unit force acts on the bottom of the foundation pit:

[0118]

[0119] A i , B i , C i , D i By looking up the table in Table L.0.8 of the Code for Design of Highway Bridge and Culvert Foundations, we can get:

[0120] i <![CDATA[A i ]]> <![CDATA[B i ]]> <![CDATA[C i ]]> <![CDATA[D i ]]> 3 -1.61428 -11.73066 -17.91860 -15.07550 4 9.24368 -0.35762 -15.61050 -23.14040

[0121] When H0=1:

[0122] Horizontal displacement

[0123] Angle (rad) When M0=1:

[0124] Horizontal displacement

[0125] Angle (rad)

[0126] 5) Displacement of steel sheet piles at the bottom of foundation pit:

[0127] Horizontal displacement

[0128] Angle (rad)

[0129] 6) Horizontal displacement of the front row pile top

[0130]

[0131] (3) Calculate the horizontal displacement of the top of the rear piles. The calculation diagram is as follows: Fig. 9 shown.

[0132] 1) Requirements for embedding depth of steel sheet piles

[0133] Back row piles: α(h+h1)=8.005>2.5

[0134] 2) Effects of rear row piles:

[0135]

[0136] 3) The displacement of the section when a unit force acts on the bottom of the foundation pit.

[0137]

[0138] A i , B i , C i , D i By looking up the table in Table L.0.8 of the Code for Design of Highway Bridge and Culvert Foundations, we can get:

[0139] i <![CDATA[A i ]]> <![CDATA[B i ]]> <![CDATA[C i ]]> <![CDATA[D i <!-- 7 -->]]> 3 -1.61428 -11.73066 -17.91860 -15.07550 4 9.24368 -0.35762 -15.61050 -23.14040

[0140] When H0=1:

[0141] Horizontal displacement

[0142] Angle (rad) When M0=1:

[0143] Horizontal displacement

[0144] Angle (rad)

[0145] 4) Displacement of steel sheet piles at the bottom of foundation pit:

[0146] Horizontal displacement

[0147] Angle (rad)

[0148] 5) Horizontal displacement of the rear row pile top

[0149]

[0150] (4) Iterative calculation of the displacement of the tops of the front and rear rows of piles

[0151] 1)Δ 前 >Δ 后 , increase the rod tension H for iterative calculation;

[0152] 2) After multiple iterations, H = 50.476 kN, Δ 前 =Δ 后 =1.665×10 -2 m.

[0153] γ is set to 1.0, and the final pile top displacement is

[0154] Δ=γΔ 前 or γΔ 后 =1.665×10 -2 m=16.6mm

[0155] The above are the results calculated by the method of the present invention.

[0156] According to the method of "Technical Code for Building Foundation Pit Support" JGJ120-2012, the double-row pile module in the Lizheng Deep Foundation Pit 7.0BP5 software is used for calculation. In this example, the steel sheet pile is replaced by C30 concrete pile according to the bending stiffness, with a cross-sectional size of 0.4*0.433m (width*height), and the connecting rod φ32mm steel bar is replaced by a concrete connecting beam according to the EA stiffness, with a cross-sectional size of 0.045*0.045m. The crown beam is set to none. The calculation parameter settings and calculation results are shown as follows: Fig.10 and 11 shown.

[0157] The above is the calculation result of the standard method, and the pile top displacement is 113.7mm.

[0158] According to the actual monitoring results of the foundation pit, Fig.12As shown in the figure, the displacement value of the foundation pit is between 6.3 and 26.2 mm, and the middle value is about 11.8-22.4. The displacement value calculated by the present invention is 16.6 mm, which is very close to the actual project. However, the displacement result calculated by the software using the standard method is 113.7 mm, which is seriously deviated from the actual project and has basically no reference value.

[0159] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for analyzing internal forces and displacements of a double-row steel sheet pile support structure, characterized in that: The following steps are involved: The double-row steel sheet piles include the front row piles and the rear row piles. The tops of the two piles are connected by tie rods. The tensile elongation of the tie rods is ignored. According to the relative position relationship between the rear row piles and the active earth pressure rupture surface, the modified earth pressure at the bottom of the front row pile foundation pit and the active earth pressure resultant of the rear row piles are calculated respectively. The front row of piles is regarded as a single row of piles, a tension force is set, and the distributed modified earth pressure is applied to the front row of piles to calculate the displacement of the top of the front row of piles; The rear row piles are regarded as ordinary piles that are cantilevered above the intersection of the fracture surfaces, the tension rod force acts on the pile top, and the distributed active earth pressure resultant force acts on the rear row piles to calculate the displacement of the rear row pile tops; Ignoring the influence of the tension rod deformation, the tension rod force is adjusted through repeated iterations until the displacement of the top of the front row piles is equal to the displacement of the top of the rear row piles, the iteration is terminated, and the displacement of the top of the double row of steel sheet piles at this time and the corresponding internal force state are output; The calculation method of the modified earth pressure is: ； In the formula, is the active earth pressure force on the double-row steel sheet piles, is the active earth pressure force on the rear row piles, It is the height from the bottom of the foundation pit to the intersection of the fracture surface and the rear row of piles; It is the height from the ground to the intersection of the rupture surface and the rear row of piles.

2. The internal force and displacement analysis method of the double-row steel sheet pile support structure according to claim 1 is characterized in that: The calculation method of the displacement of the top of the front row piles is: ； In the formula, is the horizontal displacement at the bottom of the front row pile foundation pit, is the corner at the bottom of the front row of pile foundation pit. It is the height from the bottom of the foundation pit to the intersection of the fracture surface and the rear row of piles. is the height from the ground to the intersection of the fracture surface and the rear row of piles, It is the displacement of the pile top caused by the elastic deflection of the front row of piles above the pit bottom.

3. The internal force and displacement analysis method of the double-row steel sheet pile support structure according to claim 1 is characterized in that: The calculation method of the displacement of the top of the rear row piles is: ； In the formula, is the horizontal displacement at the bottom of the front row pile foundation pit, is the corner at the bottom of the front row of pile foundation pit. is the height from the ground to the intersection of the fracture surface and the rear row of piles, It is the displacement of the pile top caused by the elastic deflection of the rear row of piles above the pit bottom.

4. The internal force and displacement analysis method of the double-row steel sheet pile support structure according to claim 1 is characterized in that: The pile top displacement of the double-row steel sheet pile is: ； In the formula, is the correction factor, is the displacement of the top of the front row piles, is the displacement of the top of the rear row of piles.

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