Stiffness correction analysis method for optimization design of pile-anchor-soil combined system

Abstract

The application discloses a two-stage stiffness correction method based on a pile-anchor-soil pressure-pulling composite system optimization, and steps are as follows: 1, basic parameter preparation; the column net of the underground engineering needing correction is divided into blocks; wherein, the area shared by each single column is determined as a calculation area; when any calculation area is a column pressure-bearing area, pressure-bearing piles are arranged according to the pressure-bearing calculation needs; when any calculation area is a plate span area, anti-floating components are arranged; 2, process calculation parameters of punching cone, anchor composite elastic modulus and pile-anchor pressure-pulling bearing capacity are determined; 3, an analysis model is established; 4, preliminary estimation analysis; 5, model refinement analysis, the analysis model and its boundary conditions are corrected by using the parameter variables corrected by the preliminary estimation analysis; the analysis model is updated by relying on a general finite element software and is solved again. The application can realize internal force redistribution between the pile foundation in the pressure-bearing area, the anti-floating component in the plate span area and the bottom plate, and solves the defects of the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of computer-aided design, in particular to a stiffness correction analysis method for optimization design of pile-anchor-soil pressure-pulling composite system. BACKGROUND

[0002] Anti-uplift pile and anti-float anchor are commonly used components for anti-floating of underground engineering. The existing design methods for anti-floating components of underground engineering mainly include:

[0003] 1) Uniform arrangement method. The number of anti-floating components is calculated according to the unbalanced force of the whole calculated area of underground engineering resisting the floating force. This method assumes that each anti-floating component uniformly shares the uplift force, each component has the same design parameter, and the anti-floating components are uniformly arranged in the anti-floating area of the bottom plate of underground engineering.

[0004] However, the above-mentioned first method has the following disadvantages:

[0005] (1) The load-carrying capacity of each component cannot be fully utilized according to the actual stress condition;

[0006] (2) The thickness of the bottom plate of underground engineering does not reflect the different stress characteristics of the column compression zone and the plate span area under compression and anti-floating conditions.

[0007] 2) Non-uniform arrangement method. The column compression zone is provided with compression zone pile foundation which does not participate in anti-floating, and only the anti-floating component is arranged in the plate span area. This method assumes that the column pile foundation plays a load-carrying role under compression condition, and the anti-floating component in the plate span area plays an anti-floating role under anti-floating condition.

[0008] However, the above-mentioned second method has the following disadvantages:

[0009] The column pile foundation and the anti-floating component independently play their respective roles under their respective conditions, and the load-carrying capacity of each is not fully utilized.

[0010] Due to the differences between the assumptions of the above two existing design methods and the actual stress state of underground engineering structure, the load-carrying capacity of the anti-floating component and the bottom plate of underground engineering is not fully utilized, and the anti-floating design and engineering measures are not economical.

[0011] Therefore, how to solve the defects of the traditional anti-floating design method of underground engineering, that is, the load-carrying capacity of the anti-floating component and the bottom plate of underground engineering is not fully utilized, and the anti-floating design and engineering measures are not economical, has become a technical problem to be solved by the technical personnel in the field. SUMMARY

[0012] In view of the above defects of the prior art, the present application provides a stiffness correction analysis method for pile-anchor-soil compression-pulling composite system optimization design, which realizes the redistribution of internal forces between the pile foundation in the pressure zone, the anti-floating member in the plate span zone and the bottom plate, forms a compression-pulling composite system which fully develops the bearing capacity of each component, and solves the defects of the prior art.

[0013] To achieve the above-mentioned purpose, the present application discloses a stiffness correction analysis method for pile-anchor-soil compression-pulling composite system optimization design, which comprises the following steps:

[0014] Step 1, basic parameter preparation;

[0015] The column grid of the underground engineering which needs to be corrected is divided into blocks;

[0016] Each single column shares an area which is determined as a calculation area;

[0017] The length of each calculation area is L and the width is B;

[0018] When any calculation area is the pressure zone under the column, pressure piles are arranged according to the pressure calculation needs;

[0019] When any calculation area is the plate span zone, anti-floating members are arranged;

[0020] Step 2, determining the process calculation parameters of the punching cone, the composite elastic modulus of the anchor rod and the compression-pulling bearing capacity of the pile and anchor;

[0021] Step 3, establishing an analysis model;

[0022] Step 4, preliminary estimation analysis;

[0023] Step 5, model refinement analysis, using the parameter variables corrected by the preliminary estimation analysis, correcting the analysis model and its boundary conditions; relying on the general finite element software to update the analysis model established in step 3 and solve it again.

[0024] Preferably, any pressure pile under the anti-floating working condition is also used as an anti-pulling pile.

[0025] Preferably, the anti-floating member is an anti-floating anchor rod or an anti-pulling pile.

[0026] Preferably, step 1 comprises the following steps:

[0027] Step 1.1, model analysis and determination of basic dimensions for each calculation area; the length of the calculation area under each single column is L and the width is B; the column section of each single column is bz x bh; the diameter of the pile foundation in each pressure zone is dp;

[0028] Step 1.2, load calculation, specifically: calculating the total anti-floating force standard value W of each calculation area, calculating the bottom plate floating force standard value Ff of each calculation area, the column bottom axial force standard value Fn of the corresponding single column, and the bottom plate weight Gjk of the corresponding column bearing area when the corresponding calculation area is a column bearing area;

[0029] Step 1.3, determining physical parameters, specifically: determining the elastic modulus Es of the anti-floating anchor rod body as the anti-floating member, the elastic modulus Em of the grouting consolidation body, and determining the elastic modulus Ec of the pile body as the bearing pile;

[0030] Step 1.4, determining foundation parameters, including foundation bearing capacity [fa], foundation base coefficient Kso, pile side friction resistance qsk, and pile tip resistance qpk;

[0031] Step 1.5, preliminary variable parameters, including the size bd×bd of the bearing area corresponding to each single column, the structural thickness hb of the bearing area, and the structural thickness ht when the corresponding calculation area is a plate span area, the diameter dp, pile end area Ap, pile length hp, and pile spacing sp when the bearing pile serves as an anti-pulling pile, the anchor rod body cross-sectional area As of the anti-floating anchor rod as the anti-floating member, the grouting consolidation body cross-sectional area Aj, the anchor rod free section length lf, the anchor rod length lr, and the anchor rod spacing sr;

[0032] Step 1.6, determining safety guarantee coefficients, including permanent load sub-item coefficient γg, structure importance coefficient γ0, and anti-floating safety coefficient K.

[0033] More preferably, in step 2, the process calculation parameters of the punching cone are as follows:

[0034] The effective section height of the column punching cone hb0 = hb - as;

[0035] Where as is the distance from the main stress steel to the nearest concrete surface;

[0036] The bottom surface side length of the column punching cone bq = bz + 2hb0, hq = hz + 2hb0;

[0037] The bottom surface area of the column punching cone Aq = bq × hq;

[0038] The critical section side length of the column punching cone bm and hm, i.e. the side length at the position of half of the effective section height hb0 of the column punching cone bm = bz + hb0, hm = hz + hb0,

[0039] The critical section area of the column punching cone Am = bm × hm;

[0040] The weight of the column punching cone Gm = γc × Am × hb;

[0041] wherein γc is the unit weight of reinforced concrete;

[0042] The composite elastic modulus of the anchor rod Esm = [Es × As + Em × (Aj- As)] / Aj;

[0043] The pile, anchor, and pressure-pulling bearing capacity include the anchor rod uplift bearing capacity Tr, the single pile uplift bearing capacity Tp, and the single pile pressure bearing capacity Rp.

[0044] More preferably, step 3 comprises the following steps:

[0045] Step 3.1, component model, specifically: a finite element model is established according to the designed size of the underground structure top plate, middle plate, bottom plate, column, and each layer beam;

[0046] The bottom plate is divided into a column pressure bearing area and a plate span area;

[0047] The side length of the column pressure bearing area is bd, and the structure height is hb;

[0048] The plate thickness of the plate span area is ht;

[0049] Step 3.2, determine the load, specifically: load is applied according to the self-weight of the underground structure beam, plate, and column, the load is applied in the form of load on the top plate according to the soil depth, the live load above the ground is converted into an overload to apply load, the middle plate and the bottom plate are paved according to the paving load to apply load, and the bottom plate is subjected to a buoyancy load according to the underground water level;

[0050] Step 3.3, boundary condition, specifically: for each calculation area, the modeling range is expanded, the boundary is constrained by a connecting rod; the vertical constraint of the corresponding pressure bearing area foundation to the bottom plate is simulated by a compression spring only, and the spring stiffness is taken as the foundation stiffness Kj; the pressure bearing area pile foundation is simulated by a linear spring, and the spring stiffness is taken as the single pile shaft stiffness Kp; the corresponding plate span area uplift component is simulated by a linear spring, and the spring stiffness is taken as the elastic stiffness Kr of a single anchor rod.

[0051] More preferably, step 4 comprises the following steps:

[0052] Step 4.1, determine the number of calculation area anti-floating components;

[0053] The overall unbalanced force of each calculation area resisting the floating force is calculated, that is, the total uplift force Fb of the corresponding calculation area K × Ff-W; if Fb ≤ 0 is satisfied, no anti-floating component is needed;

[0054] If Fb≤0 is not met, it is assumed that the bearing area and the plate span area each bear 1 / 2 of the total uplift force Fb, the number of bearing piles as uplift piles n1=Fb / (2Tp), and the pile spacing sp∈(2d, 3d); the number of uplift anchor bars arranged in the plate span area n2=(Fb-n1*Tp) / Tr, and the anchor bar spacing sr is 1.2m to 1.5m;

[0055] Step 4.2, determine the bearing area pile foundation stiffness, anti-floating component stiffness and foundation stiffness, as follows:

[0056] The calculation formula of the elastic stiffness Kr of a single anchor bar is as follows:

[0057] Kr=3Es×Esm×As×Aj / [3Esm×Aj×Lf+Es×As×(lr-lf)];

[0058] The single pile shaft stiffness Kp=Ec×Ap / hp;

[0059] The foundation stiffness K2=Kj=Kso×(Ad-Ap*n1);

[0060] The total stiffness of the bearing pile K1=n1×Kp;

[0061] The total stiffness of the uplift anchor bar in the plate span area K3=n2×Kr;

[0062] Step 4.3, determine the bearing area range, as follows:

[0063] Column under bearing area range estimation: Ad=Fn / ([fa]-γc×hb)

[0064] The column under bearing area side length bd=sqrt(Ad), if bd≤min(B / 3, L / 3) is met, when the column under bearing area can not be provided with bearing piles, n1=0;

[0065] The punching load Fqd=γ0×γg×(Fn+Gm-p×Aq);

[0066] Then, check whether the column under anti-punching section meets the anti-punching requirement, if not, increase hb and repeat step 4.3 until the anti-punching requirement is met;

[0067] Step 4.4, bearing area pile foundation initial variable parameter correction, if the column under bearing area side length does not meet bd≤min(B / 3, L / 3), the load of the bearing area pile foundation and the foundation under the bearing condition is distributed according to the stiffness ratio, as follows:

[0068] The bearing pile shares the total load F1=Fjk*k1 / (k1+k2),

[0069] The single bearing pile shares the load F1s=F1 / n1;

[0070] Total load of foundation Fjk=Fn+Gjk,

[0071] The pressure zone foundation reaction p=(Fjk-F1) / (Ad-Ap*n1);

[0072] If the requirements of F1s≤Rp and p≤[fa] are not met, modify hp and dp, and repeat steps 2 to 4.4 to recalculate Rp until the requirements of F1s≤Rp and p≤[fa] are met;

[0073] Step 4.5, initial variable parameter correction of the anti-floating member in the plate span area, if the pile foundation in the pressure zone determined according to step 4.4 is considered to be used as an anti-pulling pile together with the anti-floating member in the plate span area to distribute the total uplift force Fb according to the stiffness ratio described in 4.1, the specific steps are as follows:

[0074] The total anti-pulling force of the pile foundation T1=Fb*k1 / (k1+k3);

[0075] The anti-pulling force of a single pile T1s=T1 / n1;

[0076] The total anti-pulling force of the anti-floating anchor T2=Fb-T1,

[0077] The anti-pulling force of a single anchor T2s=T2 / n2;

[0078] If the requirement of T2s≤Tr is not met, modify As and lr, and repeat steps 2 to 4.5 to recalculate Tp and Tr until the requirements of T1s≤Tp and T2s≤Tr are met;

[0079] Step 4.6, re-perform step 4.2 to obtain new Kp, Kr and Kj.

[0080] More preferably, step 5 includes the following steps:

[0081] Step 5.1, checking the bearing capacity of the pressure zone foundation and the bearing capacity of the pressure pile under pressure working condition, the specific steps are as follows:

[0082] Extract the analysis results of the foundation node reaction Rji and the pressure zone pile node reaction Rci;

[0083] Check the bearing capacity of the foundation, the bearing capacity of the foundation p=∑Rji / (Ad-Ap*n1), which needs to meet the requirement of p≤[fa];

[0084] Check the single pile bearing capacity, which needs to meet the requirement of Rci≤Rp;

[0085] If not, adjust dp and hp, and repeat steps 2 to 5.1 to recalculate Rp until Rci≤Rp is met;

[0086] Step 5.2, the bearing capacity of the pile foundation in the pressure area under the anti-floating working condition, and the bearing capacity of the anti-floating component in the slab span area is checked, and the specific steps are as follows:

[0087] The node reaction force Rpi of the anti-floating pile foundation in the pressure area and the node reaction force Rri of the anti-floating anchor in the slab span area are extracted for analysis;

[0088] For checking the bearing capacity of the pile foundation in the pressure area, Rpi must satisfy Tp.

[0089] For checking the bearing capacity of the anti-floating anchor in the slab span area, Rri must satisfy Tr.

[0090] For checking the uniformity of the uplift force shared by the pile foundation in the pressure area and the anti-floating anchor in the slab span area, 0.75≤∑Rpi / ∑Rri≤1.25 must be satisfied.

[0091] If Rpi≤Tp, Rri<=Tr, and 0.75≤∑Rpi / ∑Rri≤1.25 cannot be satisfied at the same time, adjust (As, lr) and n2, and repeat steps 2 to 5.2 to recalculate Kr until the conditions are satisfied.

[0092] Step 5.3, the thickness ht of the slab span structure is optimized, and the specific steps are as follows: the bending moment M and shear force Q of each node in the slab span are extracted, the crack vi is calculated, and the cross-sectional height ht that satisfies the bearing requirements and normal use requirements is selected.

[0093] The beneficial effects of the present application are as follows:

[0094] The present application can achieve internal force redistribution between the pile foundation in the pressure area, the anti-floating component in the slab span area, and the bottom plate, and solve the defects of the prior art.

[0095] The concept, specific structure, and technical effects of the present application will be further described below with reference to the accompanying drawings to fully understand the purpose, features, and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0096] Figure 1 A flowchart of an embodiment of the present application is shown.

[0097] Figure 2 A flowchart of steps 1 to 4.1 in an embodiment of the present application is shown.

[0098] Figure 3 A flowchart of steps 4.2 to 4.5 in an embodiment of the present application is shown.

[0099] Figure 4 A flowchart of steps 4.6 to 5.3 in an embodiment of the present application is shown.

[0100] Figure 5 A schematic diagram of the column grid of the underground engineering is shown.

[0101] Figure 6 Fig. 1 shows a schematic diagram of a column grid profile of an underground project in an embodiment of the present application.

[0102] Figure 7 Fig. 2 shows a schematic diagram of a anti-float load distribution of a calculation area in an embodiment of the present application.

[0103] Figure 8 Fig. 3 shows a schematic diagram of a bottom plate plane of a calculation area in an embodiment of the present application.

[0104] Figure 9 Fig. 4 shows a schematic diagram of a bottom layer profile of a calculation area in an embodiment of the present application.

[0105] Figure 10 Fig. 5 shows a schematic diagram of a load distribution of a calculation area in an embodiment of the present application. DETAILED DESCRIPTION

[0106] EMBODIMENT

[0107] As shown in the drawings, the stiffness correction analysis method for the optimization design of a pile-anchor-soil pressure-pulling composite system comprises the following steps: Figure 1

[0108] Step 1, basic parameter preparation;

[0109] The column grid of the underground project that needs to be corrected is divided into blocks;

[0110] Each single column bears an area which is determined as a calculation area;

[0111] The length of each calculation area is L and the width is B;

[0112] When any calculation area is a column pressure-bearing area, pressure-bearing piles are arranged according to the pressure-bearing calculation needs;

[0113] When any calculation area is a plate span area, anti-float members are arranged;

[0114] Step 2, determine the process calculation parameters of the punching cone, anchor composite elastic modulus and pile-anchor pressure-pulling bearing capacity;

[0115] Step 3, establish an analysis model;

[0116] Step 4, preliminary estimation analysis;

[0117] Step 5, model refinement analysis, using the parameter variables corrected by the preliminary estimation analysis, correcting the analysis model and its boundary conditions; relying on the general finite element software to update the analysis model established in step 3 and solve again.

[0118] ​The present application is based on preliminary estimation analysis, and in the pressure working condition, the total pressure load is distributed by the foundation and the pile under the column according to the respective stiffness ratio to determine the range of the pressure zone and the number of the pile under the column in the pressure zone;

[0119] In the buoyancy working condition, the number of the anti-floating member in the plate span zone is determined, and the stiffness of the pile under the column in the pressure zone, the stiffness of the anti-floating member in the plate span zone and the stiffness of the foundation are preliminarily estimated;

[0120] Then, based on the general finite element model, the stiffness of the pile under the column in the pressure zone and the stiffness of the anti-floating member in the plate span zone estimated preliminarily are taken as the boundary conditions of the model refined analysis, the range of the pressure zone is checked based on the model refined analysis, and whether the pile under the column in the pressure zone and the anti-floating member in the plate span zone uniformly bear the uplift force and whether the internal force distribution of the bottom plate of the underground engineering is uniform are taken as the criteria, and the design parameters of the pile under the column in the pressure zone and the anti-floating member in the plate span zone are corrected for many times, and then the stiffness of the pile under the column in the pressure zone and the stiffness of the anti-floating member in the plate span zone are corrected.

[0121] The present application estimates the range of the pressure zone and calculates the number of the anti-floating member in the calculation region in the pressure working condition and the buoyancy working condition respectively, and preliminarily estimates the stiffness of the pile under the column in the pressure zone, the stiffness of the anti-floating member in the plate span zone and the stiffness of the foundation; based on the preliminary calculation stiffness and the model refined analysis, the range of the pressure zone is checked, and the internal force redistribution between the pile under the column in the pressure zone, the anti-floating member in the plate span zone and the bottom plate is realized through the model refined analysis for many times to form the pressure-pull composite system which fully plays the bearing capacity of each part, and the stiffness of the pile under the column in the pressure zone, the stiffness of the anti-floating member in the plate span zone and the thickness of the bottom plate are continuously corrected to ensure that the pile under the column in the pressure zone, the anti-floating member in the plate span zone and the bottom plate fully play the bearing capacity, so that the engineering design is more economical and saving.

[0122] In some embodiments, any of the pressure piles also functions as the anti-pull pile in the buoyancy working condition.

[0123] In some embodiments, the anti-floating member is the anti-floating anchor or the anti-pull pile.

[0124] As shown in Figure 1 and Figures 5 to 9 in some embodiments, step 1 includes the following steps:

[0125] Step 1.1, model analysis is performed on each calculation region and the basic size is determined; the length of the calculation region under each single column is L, and the width is B; the column section of each single column is bz x bh; and the diameter of the pile in each pressure zone is dp;

[0126] Step 1.2, load calculation, specifically: calculating the total anti-floating force standard value W of each calculation region, calculating the plate buoyancy standard value Ff of each calculation region, calculating the column bottom axial force standard value Fn of the corresponding single column, and when the corresponding calculation region is the column pressure zone, calculating the plate weight Gjk of the corresponding column pressure zone;

[0127] Step 1.3, determining physical parameters, specifically: determining the elastic modulus of the anti-float anchor rod body Es as an anti-float member, the elastic modulus of the grouting consolidation body Em, and determining the elastic modulus of the pile body Ec as a pressure-bearing pile;

[0128] Step 1.4, determining foundation parameters, including foundation bearing capacity [fa], foundation base coefficient Kso, pile side friction resistance qsk, and pile tip resistance qpk;

[0129] Step 1.5, initially determining variable parameters, including the size bd x bd of the pressure-bearing area corresponding to each single column, the structural thickness hb of the pressure-bearing area, and the structural thickness ht when the corresponding calculation area is a slab span area, the diameter dp of the pressure-bearing pile serving as an uplift pile, the pile tip area Ap, the pile length hp, and the pile spacing sp, the anchor rod body cross-sectional area As of the anti-float anchor as an anti-float member, the grouting consolidation body cross-sectional area Aj, the anchor rod free section length lf, the anchor rod length lr, and the anchor rod spacing sr;

[0130] Step 1.6, determining safety assurance coefficients, including the permanent load sub-item coefficient γg, the structure importance coefficient γ0, and the anti-float safety coefficient K.

[0131] In some embodiments, in step 2, the process of punching the cone has the following calculation parameters:

[0132] The effective sectional height of the column under the punched cone hb0 = hb - as;

[0133] Where as is the distance from the main stress reinforcement to the nearest concrete surface;

[0134] The bottom side length of the column under the punched cone bq = bz + 2hb0, hq = hz + 2hb0;

[0135] The bottom area of the column under the punched cone Aq = bq x hq;

[0136] The critical sectional side length of the column under the punched cone bm and hm, i.e., the side length at the position of half the effective sectional height hb0 of the column under the punched cone bm = bz + hb0, hm = hz + hb0,

[0137] The critical sectional area of the column under the punched cone Am = bm x hm;

[0138] The weight of the column under the punched cone Gm = γc x Am x hb;

[0139] Where γc is the unit weight of reinforced concrete;

[0140] The composite elastic modulus of the anchor Esm = [Es x As + Em x (Aj - As)] / Aj;

[0141] The pile, anchor pull-out bearing capacity includes anchor rod uplift bearing capacity Tr, single pile uplift bearing capacity Tp, and single pile pressure bearing capacity Rp.

[0142] The anchor rod uplift bearing capacity Tr, the single pile uplift bearing capacity Tp, and the single pile pressure bearing capacity Rp are calculated by the conventional technique in the art and can be obtained according to the Technical Code for Building Pile Foundation (JGJ94).

[0143] As shown in Figure 1 and Figure 10 In some embodiments, step 3 includes the following steps:

[0144] Step 3.1, component model, specifically: finite element models are established according to the designed sizes of the top plate, the middle plate, the bottom plate, the column, and the beams of each layer of the underground structure;

[0145] The bottom plate is divided into a column pressure bearing area and a plate span area.

[0146] The side length of the column pressure bearing area is bd, and the structure height is hb.

[0147] The plate thickness of the plate span area is ht.

[0148] Step 3.2, load determination, specifically: loads are applied according to the self-weight of the beams, plates, and columns of the underground structure, the load in the form of load is applied according to the earth covering depth above the top plate, the load in the form of overload is applied according to the live load above the ground, the load in the form of paving load is applied according to the paving load above the middle plate and the bottom plate, and the buoyancy load is applied according to the underground water level of the bottom plate.

[0149] Step 3.3, boundary condition, specifically: for each calculation area, the modeling range is expanded, the boundary is constrained by a connecting rod; the vertical constraint of the corresponding pressure bearing area foundation to the bottom plate is simulated by a compression spring, and the spring stiffness is taken as the foundation stiffness Kj; the pressure bearing area pile foundation is simulated by a linear spring, and the spring stiffness is taken as the single pile shaft stiffness Kp; the corresponding plate span area uplift component is simulated by a linear spring, and the spring stiffness is taken as the elastic stiffness Kr of a single anchor rod.

[0150] As shown in Figures 1 to 4 In some embodiments, step 4 includes the following steps:

[0151] Step 4.1, determining the number of anti-floating components of the calculation area;

[0152] The unbalanced force of the whole anti-floating force of each calculation area, i.e., the total uplift force Fb of the corresponding calculation area, is KxFf-W; if Fb≤0 is satisfied, no anti-floating component is needed.

[0153] If Fb≤0 is not met, it is assumed that the bearing area and the plate span area each bear 1 / 2 of the total uplift force Fb, the number of bearing piles as uplift piles n1=Fb / (2Tp), and the pile spacing sp∈(2d, 3d); the number of uplift anchor bars arranged in the plate span area n2=(Fb-n1*Tp) / Tr, and the anchor bar spacing sr is 1.2m to 1.5m;

[0154] Step 4.2, determine the bearing area pile foundation stiffness, anti-floating component stiffness and foundation stiffness, as follows:

[0155] The calculation formula of the elastic stiffness Kr of a single anchor bar is as follows:

[0156] Kr=3Es×Esm×As×Aj / [3Esm×Aj×Lf+Es×As×(lr-lf)];

[0157] The single pile shaft stiffness Kp=Ec×Ap / hp;

[0158] The foundation stiffness K2=Kj=Kso×(Ad-Ap*n1);

[0159] The total stiffness of the bearing pile K1=n1×Kp;

[0160] The total stiffness of the uplift anchor bar in the plate span area K3=n2×Kr;

[0161] Step 4.3, determine the bearing area range, as follows:

[0162] The bearing area range under the column is estimated as Ad=Fn / ([fa]-γc×hb)

[0163] The column bearing area side length bd=sqrt(Ad), if bd≤min(B / 3, L / 3) is met, the bearing pile under the column can not be set, and n1=0;

[0164] The punching load Fqd=γ0×γg×(Fn+Gm-p×Aq);

[0165] Then, check whether the column anti-punching section meets the anti-punching requirements, if not, increase hb and repeat step 4.3 until the anti-punching requirements are met;

[0166] Step 4.4, bearing area pile foundation initial variable parameter correction, if the column bearing area side length does not meet bd≤min(B / 3, L / 3), the load of the bearing area pile foundation and the foundation under the bearing condition is distributed according to the stiffness ratio, as follows:

[0167] The bearing pile shares the total load F1=Fjk*k1 / (k1+k2),

[0168] The single bearing pile shares the load F1s=F1 / n1;

[0169] Total base load Fjk=Fn+Gjk,

[0170] The soil reaction force in the pressure zone is p = (Fjk - F1) / (Ad - Ap * n1);

[0171] If the requirement of F1s≤Rp and p≤[fa] is not met, correct hp and dp, repeat steps 2 to 4.4, recalculate Rp, until the requirement of F1s≤Rp and p≤[fa] is met;

[0172] Step 4.5: Correction of initial variable parameters for the anti-buoyancy components in the slab span area. If, under anti-buoyancy conditions, the pile foundation in the bearing zone determined in Step 4.4 is considered to also serve as an anti-uplift pile, and together with the anti-buoyancy components in the slab span area, the total uplift force Fb described in 4.1 is distributed according to the stiffness ratio, as follows:

[0173] The total pull-out force shared by the pile foundation is T1 = Fb*k1 / (k1+k3);

[0174] The pull-out force of a single pile foundation is T1s = T1 / n1;

[0175] The anti-buoyancy anchor bolt shares the total pull-out force T2=Fb-T1,

[0176] Pull-out force of a single anchor bolt: T2s = T2 / n2;

[0177] If the requirement T2s≤Tr is not met, correct As and lr, repeat steps 2 to 4.5, recalculate Tp and Tr until the requirements T1s≤Tp and T2s≤Tr are met.

[0178] Step 4.6: Repeat step 4.2 to obtain new Kp, Kr, and Kj.

[0179] In practical applications, the process of verifying whether the punching shear section under the column meets the punching shear requirements in step 4.3 shall be carried out in accordance with the conventional techniques in this field disclosed in the Code for Concrete Structures (GB50010).

[0180] like Figure 4 As shown, in some embodiments, step 5 includes the following steps:

[0181] Step 5.1: Verification of the bearing capacity of the foundation soil in the pressure zone and the bearing capacity of the pressure pile foundation under pressure conditions, as detailed below:

[0182] Extract the analysis results of the ground joint reaction force Rji and the pile joint reaction force Rci in the compression zone;

[0183] The foundation bearing capacity is checked. The foundation bearing capacity p = ∑Rji / (Ad-Ap*n1) must satisfy the requirement that p ≤ [fa].

[0184] The single pile pressure bearing capacity check needs to meet Rci<=Rp;

[0185] If not, adjust dp and hp, repeat steps 2 to 5.1, recalculate Rp, until Rci<=Rp is met.

[0186] Step 5.2, check the uplift bearing capacity of the pile foundation in the pressure zone and the uplift bearing capacity of the anti-floating member in the plate span area under the anti-floating working condition, as follows:

[0187] Extract the analysis results of the reaction force Rpi of the anti-floating pile foundation node in the pressure zone and the reaction force Rri of the anti-floating anchor node in the plate span area.

[0188] Check the uplift bearing capacity of the pile foundation in the pressure zone, which needs to meet Rpi<=Tp;

[0189] Check the uplift bearing capacity of the anti-floating anchor in the plate span area, which needs to meet Rri<=Tr;

[0190] Check the uniformity of the uplift force shared by the pile foundation in the pressure zone and the anti-floating anchor in the plate span area, which needs to meet 0.75<=∑Rpi / ∑Rri<=1.25;

[0191] If Rpi<=Tp, Rri<=>Tr, and 0.75<=∑Rpi / ∑Rri<=1.25 cannot be met simultaneously, adjust (As, lr) and n2, repeat steps 2 to 5.2, recalculate Kr, until it is met.

[0192] Step 5.3, optimize the thickness ht of the plate span structure, which is: extract the bending moment M and shear force Q of each node in the plate span, calculate the crack vi, and optimize the selection of the cross-sectional height ht that meets the bearing requirements and normal use requirements.

[0193] In practical applications, the process of optimizing the selection of the cross-sectional height ht that meets the bearing requirements and normal use requirements in step 5.3 is performed according to the conventional techniques disclosed in the Concrete Structure Specification (GB 50010).

[0194] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the existing technology according to the concept of the present application shall be within the protection scope determined by the claims.

Claims

1. A stiffness correction analysis method for the optimal design of pile-anchor-soil uplift composite system; characterized in that, It comprises the following steps: Step 1, basic parameter preparation; The underground engineering column grid is divided into blocks according to the need for correction; Each single column area is determined as a calculation area; The length of each calculation area is L and the width is B; When any calculation area is a column pressure zone, a pressure pile is arranged according to the need for pressure calculation; When any calculation area is a plate span area, an anti-floating member is arranged; Step 2, process calculation parameters of punching shear cone and anchor rod composite elastic modulus and pile and anchor pressure bearing capacity are determined; The process calculation parameters of the punching shear cone are as follows: The effective section height of the column punching shear cone hb0=hb-as; Wherein as is the distance from the main stress steel to the nearest concrete surface; The bottom side length of the column punching shear cone bq=bz+2hb0, hq=hz+2hb0; The bottom area of the column punching shear cone Aq=bq×hq; The critical section side length of the column punching shear cone bm and hm, which is located at the position of half of the effective section height of the column punching shear cone hb0, bm=bz+hb0, hm=hz+hb0, The critical section area of the column punching shear cone Am=bm×hm; The weight of the column punching shear cone Gm=γc×Am×hb; Wherein γc is the unit weight of reinforced concrete; The composite elastic modulus of the anchor rod Esm=[Es×As+Em×(Aj-As)] / Aj; The pile and anchor pressure bearing capacity includes anchor rod uplift capacity Tr, single pile uplift capacity Tp, and single pile pressure bearing capacity Rp; Step 3, an analysis model is established; Step 4, preliminary estimation analysis; Step 5, model refinement analysis, using the parameter variables corrected by the preliminary estimation analysis, the analysis model and its boundary conditions are corrected; relying on the general finite element software to update the analysis model established in step 3 and solve again.

2. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 1, characterized in that, Any of the pressure piles in the anti-floating working condition also serves as an uplift pile.

3. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 1, characterized in that, The anti-floating member is an anti-floating anchor rod or an uplift pile.

4. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 1, characterized in that, Step 1 comprises the following steps: Step 1.1, model analysis and determination of basic dimensions are performed for each calculation area; the length of the column calculation area of each single column is L, and the width is B; the column section of each single column is bz×bh; the diameter of the pile foundation in each pressure zone is dp; Step 1.2, load calculation, specifically: calculating the total anti-floating force standard value W of each calculation area, calculating the bottom plate buoyancy standard value Ff of each calculation area, the column bottom axial force standard value Fn of the corresponding single column, and the bottom plate weight Gjk of the corresponding column pressure zone when the corresponding calculation area is a column pressure zone; Step 1.3, physical parameters are determined, specifically: the elastic modulus of the anti-floating anchor rod body Es, the elastic modulus of the grouting consolidation body Em as the anti-floating member, and the pile body elastic modulus Ec as the pressure pile are determined; Step 1.4, foundation parameters are determined, including foundation bearing capacity [fa], foundation bed coefficient Kso, pile side friction resistance qsk, and pile tip resistance qpk; Step 1.5, preliminary variable parameters, including the size bd×bd of the bearing area corresponding to each single column, the structural thickness hb of the bearing area, and the structural thickness ht when the corresponding calculation area is a slab span area, the diameter dp of the bearing pile serving as a uplift pile, the pile end area Ap, the pile length hp and the pile spacing sp, the anchor rod body cross-sectional area As of the anti-floating anchor rod as the anti-floating component, the grouting consolidation body cross-sectional area Aj, the anchor rod free section length lf, the anchor rod length lr and the anchor rod spacing sr; Step 1.6, determine the safety guarantee coefficient, including the permanent load sub-item coefficient γg, the structural importance coefficient γ0 and the anti-floating safety coefficient K.

5. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 4, characterized in that, Step 3 includes the following steps: Step 3.1, component model, specifically: a finite element model is established according to the designed size through the underground structure top plate, middle plate, bottom plate, column and each layer beam; Wherein, the bottom plate is divided into a column bearing area and a slab span area; The side length of the column bearing area is bd, and the structural height is hb; The slab thickness of the slab span area is ht; Step 3.2, determine the load, specifically: load is applied according to the self-weight of the underground structure beam, plate and column, the load is applied in the form of load on the top plate according to the depth of the overburden, the superload is applied in the form of load by converting the live load above the ground, the load is applied according to the paving load on the middle plate and the bottom plate, and the buoyancy load is applied to the bottom plate according to the underground water level; Step 3.3, boundary conditions, specifically: for each calculation area, the modeling range is expanded, and the boundary is constrained by a connecting rod; the vertical constraint of the corresponding bearing area foundation to the bottom plate is simulated by a compression spring only, and the spring stiffness is taken as the foundation stiffness Kj; the pile foundation of the bearing area is simulated by a linear spring, and the spring stiffness is taken as the single pile shaft stiffness Kp; the corresponding slab span area anti-floating component is simulated by a linear spring, and the spring stiffness is taken as the single anchor rod elastic stiffness Kr.

6. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 5, characterized in that, Step 4 includes the following steps: Step 4.1, determine the number of anti-floating components of the calculation area; Calculate the overall unbalanced force of each calculation area resisting the floating force, that is, the total uplift force Fb=K×Ff-W of the corresponding calculation area; if Fb≤0, no anti-floating component is needed; If Fb≤0 is not met, it is assumed that the bearing area and the plate span area each bear 1 / 2 of the total uplift force Fb, the number of bearing piles as uplift piles n1=Fb / (2Tp), pile spacing sp (2d, 3d); the number of uplift anchor rods arranged in the plate span area n2=(Fb-n1*Tp) / Tr, and the anchor rod spacing sr is 1.2m to 1.5m; Step 4.2, determine the bearing area pile foundation stiffness, anti-floating component stiffness and foundation stiffness, specifically as follows: The calculation formula of the single anchor rod elastic stiffness Kr is as follows: Kr=3Es×Esm×As×Aj / [3Esm×Aj×Lf+Es×As×(lr-lf)]; The single pile shaft stiffness Kp=Ec×Ap / hp; The foundation stiffness K2=Kj=Kso×(Ad-Ap*n1); The total stiffness of the bearing pile K1=n1×Kp; The total stiffness of the slab span area anti-floating anchor rod K3=n2×Kr; Step 4.3, determine the bearing area range, specifically as follows: Column bearing area range estimation: Ad=Fn / ([fa]-γc×hb) The side length of the column bearing area bd=sqrt(Ad), if bd≤min(B / 3, L / 3) When the column bearing area can not be provided with bearing piles, n1=0; The punching load Fqd=γ0×γg×(Fn+Gm-p×Aq); Then, check whether the punching shear section under the column meets the punching shear requirement, if not, increase hb and repeat step 4.3 until the punching shear requirement is met; Step 4.4, initial variable parameter correction of the pile foundation in the bearing area, if the side length of the bearing area under the column does not meet bd≤min(B / 3, L / 3), the load of the pile foundation and the foundation in the bearing condition is distributed according to the stiffness ratio, which is as follows: The total load F1 of the bearing pile is F1=Fjk*k1 / (k1+k2), The single bearing pile F1s shares the load F1 / n1; The total load Fjk of the foundation is Fn+Gjk, The reaction force p of the foundation in the bearing area is (Fjk-F1) / (Ad-Ap*n1); If the requirements of F1s≤Rp and p≤[fa] are not met, adjust hp and dp, and repeat steps 2 to 4.4 to recalculate Rp until the requirements of F1s≤Rp and p≤[fa] are met; Step 4.5, initial variable parameter correction of the anti-floating member in the plate span area, if the pile foundation in the bearing area determined in step 4.4 is considered as an anti-pulling pile and is distributed with the anti-floating member in the plate span area according to the stiffness ratio, the total uplift force Fb in step 4.1 is distributed as follows: The total uplift force T1 of the pile foundation is T1=Fb*k1 / (k1+k3); The single pile T1s shares the uplift force T1 / n1; The anti-floating anchor T2 shares the total uplift force Fb-T1, The single anchor T2s shares the uplift force T2 / n2; If the requirement of T2s≤Tr is not met, adjust As and lr, and repeat steps 2 to 4.5 to recalculate Tp and Tr until the requirements of T1s≤Tp and T2s≤Tr are met; Step 4.6, re-execute step 4.2 to obtain new Kp, Kr and Kj.

7. The stiffness correction analysis method for the optimization design of pile-anchor-soil pressure composite system according to claim 6, characterized in that, Step 5 includes the following steps: Step 5.1, bearing capacity of the foundation in the bearing area and bearing capacity of the pile foundation in the bearing condition are checked, which is as follows: Extract the analysis results of the foundation node reaction force Rji and the bearing area pile node reaction force Rci; Check the bearing capacity of the foundation, the bearing capacity of the foundation p=∑Rji / (Ad-Ap*n1) should meet the requirement of p≤[fa]; Check the single pile bearing capacity, Rci≤Rp should be met; If not, adjust dp and hp, and repeat steps 2 to 5.1 to recalculate Rp until Rci≤Rp is met; Step 5.2, check the anti-floating bearing capacity of the pile foundation in the bearing area and the anti-floating member in the plate span area, which is as follows: Extract the analysis results of the anti-floating pile node reaction force Rpi in the bearing area and the anti-floating anchor node reaction force Rri in the plate span area; Check the anti-floating bearing capacity of the pile foundation in the bearing area, Rpi≤Tp should be met; Check the anti-floating bearing capacity of the anchor in the plate span area, Rri≤Tr should be met; Check the uniformity of the uplift force shared by the pile foundation in the bearing area and the anti-floating anchor in the plate span area, 0.75≤∑Rpi / ∑Rri≤1.25 should be met; If Rpi≤Tp, Rri<=Tr, 0.75≤∑Rpi / ∑Rri≤1.25 cannot be met simultaneously, adjust (As, lr) and n2, and repeat steps 2 to 5.2 to recalculate Kr until the conditions are met. Step 5.3, slab span structure thickness ht optimization, specifically: extract the bending moment M and shear force Q of each node of the slab span, calculate the crack vi, and optimize the selection of the section height ht that meets the bearing requirements and normal use requirements.

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