A design method of pile-column integrated short pile based on deformation and bearing capacity control

Abstract

The application discloses a design method of pile-column integrated short pile based on deformation and bearing capacity control, determines various working load conditions; judges whether to adopt a pile cap according to site soil layer conditions and pile top deformation control requirements, considers whether to reduce additional load coefficient; determines pile diameter according to engineering actual conditions; calculates foundation part deformation limit value according to pile diameter, load under normal working conditions and column top deformation control requirements; initially determines pile length, respectively calculates pile body internal force and horizontal deformation under normal working conditions and limit load conditions; checks foundation horizontal deformation under normal working conditions, checks foundation horizontal residual deformation under limit load conditions, foundation horizontal bearing capacity under limit load conditions, foundation torsional deformation under normal working conditions and foundation torsional bearing capacity under limit load conditions; determines pile type according to pile bending moment and pile crack resistance bending moment, and the crack resistance bending moment should consider the influence coefficient of horizontal-torsional load coupling effect. The calculation result of the application is reliable and meets design requirements.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of short pile design, and particularly relates to a pile-column integrated short pile design method based on deformation and bearing capacity control. BACKGROUND

[0002] With the continuous development of science and technology, power generation technology is gradually changing, and clean and environmentally friendly solar thermal power generation has become a very popular power generation method and has been widely used at home and abroad.

[0003] Solar thermal power generation is to convert solar radiation energy into heat energy of a heat transfer medium, and then heat water to form steam to drive a steam turbine generator to generate electricity. In the process of solar thermal power generation, the heliostat is the core component of the concentrating system and is the main mechanism for realizing the functions of sun tracking and day tracking. The heliostat concentrating effect directly affects the power generation efficiency, which has a higher requirement for the stiffness of the heliostat foundation, generally several hours of arc.

[0004] The commonly used heliostat support structure is a pile-column integrated foundation, which has large stiffness and low cost, but the part below the ground of this foundation belongs to a short pile foundation. At present, the research on pile foundation mainly focuses on determining the bearing capacity of long piles, and the calculation and research on the bearing capacity and deformation and residual deformation of short piles are less. At the same time, the research on the horizontal-torsional combined load of pile foundation has not formed a unified understanding, which greatly limits the application of pile foundations sensitive to deformation control. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a pile-column integrated short pile design method based on deformation and bearing capacity control. The characteristics and regularities of the short pile foundation under horizontal, torsional and horizontal-torsional coupled loads are analyzed through field tests and numerical simulation, the design method is discussed and researched in combination with the existing horizontal pile and torsional pile theory, and finally a short pile foundation design method mainly controlled by deformation and bearing capacity is proposed.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a pile-column integrated short pile design method based on deformation and bearing capacity control, comprising the following steps:

[0007] S01, determining the column top load under normal working condition SLS and ultimate load condition ULS according to process data;

[0008] S02, determining the allowable torsional angle, allowable deflection angle or allowable displacement of the column top under normal working condition SLS and the allowable residual deformation of the column top under ultimate load condition ULS according to process data;

[0009] S03, according to the site soil conditions and pile top deformation control requirements to determine whether to use pile cap, when the pile cap is set, the pile cap effect is considered, and the load under the normal working condition SLS and the ultimate load condition ULS is reduced;

[0010] S04, according to the load size of the project, the deformation requirement and the geological data to preliminarily select the pile diameter;

[0011] S05, according to the selected pile diameter, the load under the normal working condition SLS and the column top deformation control requirement to determine the foundation part deformation limit value;

[0012] S06, field pile test, determine the soil parameters;

[0013] S07, initially determine the pile length, and calculate the pile internal force and horizontal deformation under the normal working condition SLS and the ultimate load condition ULS according to the elastic foundation reaction method respectively;

[0014] S08, according to the calculation results of S07, check the foundation horizontal deformation under the normal working condition SLS, the foundation horizontal residual deformation under the ultimate load condition ULS, the foundation horizontal bearing capacity under the ultimate load condition ULS, the foundation torsional deformation under the normal working condition SLS, and the foundation torsional bearing capacity under the ultimate load condition ULS;

[0015] S09, if one of S08 does not meet the requirements, increase the pile length until all meet the requirements;

[0016] S10, according to the bending moment of the pile under the ultimate load condition ULS and the pile crack resistance bending moment obtained from S07 to determine the pile type.

[0017] In S03, when the load under the normal working condition SLS and the ultimate load condition ULS is reduced, the reduction factor α m The calculation formula is as follows:

[0018]

[0019] Wherein, B is the width of the pile cap; D is the diameter of the foundation, B is the width of the pile cap.

[0020] In S05, the column top deformation is decomposed into the deformation above the ground and the deformation below the ground, and the calculation formula is as follows:

[0021] [ φ f ]= [φ]- φ p

[0022] [ θ f ]= [ θ ]-θ p

[0023] wherein, φ f is the inclination limit value of the foundation part under the normal working condition SLS, θ f is the torsion angle limit value of the foundation part under the normal working condition (SLS), φ p is the inclination calculation value of the above-ground part column, θ p is the torsion angle calculation value of the above-ground part column,

[0024] In S07, the proportional coefficient m of the horizontal base bed coefficient used in the horizontal deformation calculation is the site test pile result m δ f The m value corresponding to the horizontal displacement limit value in the curve is multiplied by 0.4.

[0025] In S08, the following formula is used to calculate the horizontal deformation to reflect the influence of the cyclic load effect and the horizontal-torsion load coupling effect on the foundation horizontal deformation, and the foundation horizontal deformation calculation formula when calculating the cyclic load effect and the horizontal-torsion load coupling effect is as follows:

[0026]

[0027] wherein, γ c is the cyclic load effect influence coefficient, taking 1.1; γ t is the horizontal-torsion load coupling effect influence coefficient, taking 1.05, φ f is the inclination calculation value of the foundation top surface.

[0028] In S08, the horizontal residual deformation corresponding to the horizontal deformation is obtained through the residual deformation ratio, that is, the foundation horizontal residual deformation under the checking limit load condition ULS is converted into the foundation horizontal deformation under the checking limit load condition ULS.

[0029] Residual deformation ratio λ r :

[0030]

[0031] wherein, is the coefficient related to the soil properties, which is determined by the test pile, and when there is no measured data, the sand takes 0.22, the layered soil takes 0.19, and the loess takes 0.16; is the residual deformation value;

[0032] The calculation of the horizontal residual deformation limit value corresponding to the horizontal deformation limit value is as follows:

[0033]

[0034] wherein, is the rotation point depth, taking 2 L / 3, φ f,r is the residual inclination limit value of the short pile foundation after the ultimate load working condition ULS.

[0035] In S10, the foundation horizontal bearing capacity is calculated as follows:

[0036] Loess:

[0037]

[0038]

[0039] Sand:

[0040]

[0041]

[0042] wherein, h is is the column height, D is the foundation diameter, L is the foundation length, is the horizontal ultimate bearing capacity, c u is the undrained shear strength of the foundation soil; K p is the passive earth pressure coefficient, γ is the weighted average value of the pile side soil unit weight.

[0043] In S08, the foundation torsional deformation is calculated as follows:

[0044] For homogeneous soil:

[0045] For double-layer soil:

[0046] wherein, L 1 is the thickness of the first layer of soil; L 2 is the depth of the foundation inserted into the second layer of soil; G s1 is the shear modulus of the first layer of soil;

[0047] G s2Gs is the shear modulus of the second layer of soil, Rb is the radius of the foundation, θ is the calculated value of the top torsion angle of the column, L is the length of the foundation.

[0048] In S08, the ultimate torsion bearing capacity of the foundation is calculated as follows:

[0049]

[0050] wherein, T t is the bottom torsion resistance of the foundation, and the calculation formula is:

[0051]

[0052] Ts is the side torsion resistance of the foundation, and the calculation formula is:

[0053] .

[0054] In S08, the crack-resistant moment considers the horizontal-torsional load coupling effect, and the crack-resistant moment of the pile considering the horizontal-torsional load coupling effect is calculated as follows:

[0055] is the crack-resistant moment of the corresponding section of the prestressed concrete pipe pile in the drawing 10G409, T ULS is the torsion load value under the ultimate load working condition ULS.

[0056] Compared with the prior art, the present application has at least the following beneficial effects:

[0057] The short pile design method based on deformation and bearing capacity control provided by the present application gives the relationship formula of residual strain ratio and residual deformation, the calculation formula of the influence coefficient of the pile cap on the internal force and deformation of the pile body, the calculation formula of the bearing capacity of the short pile in loess and sand, the torsional deformation calculation formula of the short pile in double-layer soil, and the influence of torsional load and reciprocating cyclic load on the horizontal deformation of the pile body, etc. through a large number of indoor tests, field tests and numerical values. The short pile design method based on the deformation and bearing capacity of the pile top as control indexes is proposed. The design method considers the conditions of horizontal-torsional load coupling, cyclic load, pile cap reinforcement, etc. It fills the design blank of short pile foundation with deformation and bearing capacity as control indexes, and has universal applicability. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a schematic diagram of the pile-column integrated foundation with a pile cap of the present application;

[0059] Figure 2 is a schematic diagram of the design process of the present application;

[0060] Figure 3 A deformation decomposition schematic view of the pile integrated foundation of the present application;

[0061] Figure 4 A deformation decomposition schematic view of the pile integrated foundation of the present application; m A curve of the value changing with the displacement of the foundation mud surface;

[0062] Figure 5 A curve of the value changing with the displacement of the foundation mud surface; G s A curve of the value changing with the displacement of the foundation mud surface;

[0063] Figure 6 A curve of the value changing with the displacement of the foundation mud surface; DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0065] The pile integrated short pile structure of the present application refers to Figure 1 The present application provides a pile integrated short pile design method based on deformation and bearing capacity control, and the design process of the calculation method is shown in Figure 2 The calculation method comprises the following steps:

[0066] According to the process data, the column top load under the normal working condition SLS and the ultimate load condition ULS is determined respectively;

[0067] According to the process data, the allowable torsion angle, allowable deflection angle or allowable displacement of the column top under the normal working condition SLS and the allowable residual deformation of the column top under the ultimate load condition ULS are determined;

[0068] According to the site soil layer condition and the pile top deformation control requirement, it is determined whether to use a pile cap, if the pile cap is used, the design load should be multiplied by the load reduction coefficient ;

[0069] According to the engineering actual situation, the pile diameter is preliminarily selected;

[0070] According to the selected pile diameter, the load under the normal working condition (SLS) and the column top deformation control requirement, the deformation limit value of the foundation part is calculated;

[0071] The site test pile is determined, and the soil parameters are determined, such as drawing m A curve of the value changing with the displacement of the foundation mud surface;G s the curve of the change of the shear displacement of the pile-soil interface and the curve of the change of the residual deformation ratio and the residual displacement of the mud surface, etc.

[0072] Preliminary determination of the pile length, calculation of the internal force and horizontal deformation of the pile under the normal working condition SLS and the ultimate load condition ULS respectively according to the elastic foundation counterforce method, wherein the proportional coefficient m value of the horizontal base coefficient used in the calculation of the horizontal deformation should be taken as the site test pile result m δ f The m value corresponding to the horizontal displacement limit in the curve is multiplied by 0.4;

[0073] The horizontal deformation of the foundation under the normal working condition SLS should be checked according to the calculation result of the elastic foundation counterforce method, and the influence of the cyclic load effect and the horizontal-torsional load coupling effect on the horizontal deformation of the foundation should be considered;

[0074] The horizontal residual deformation of the foundation under the ultimate load condition ULS should be checked according to the calculation result of the elastic foundation counterforce method, and the horizontal residual deformation of the foundation under the ultimate load condition ULS is converted into the horizontal deformation of the foundation under the ultimate load condition ULS through the residual deformation ratio;

[0075] The horizontal bearing capacity of the foundation under the ultimate load condition ULS is checked;

[0076] The torsional deformation of the foundation under the normal working condition SLS is checked;

[0077] The torsional bearing capacity of the foundation under the ultimate load condition ULS is checked;

[0078] If one of the above checking results does not meet the requirements, the pile length is increased and rechecked until all the requirements are met;

[0079] The pile type is determined according to the bending moment of the pile under the ultimate load condition ULS and the crack-resistant bending moment of the pile obtained by the elastic foundation counterforce method, and the influence coefficient of the horizontal-torsional load coupling effect should be considered for the crack-resistant bending moment.

[0080] Symbols related to the resistance and stress of the foundation: m is the proportional coefficient of the horizontal base coefficient; m 0 is the proportional coefficient of the vertical base coefficient; E is the elastic modulus of the soil; E s is the compression modulus of the soil; E 0 is the deformation modulus of the soil; G s is the shear modulus / generalized shear modulus of the soil; μ is the Poisson's ratio of the soil; c u is the undrained shear strength of the soil; φ is the internal friction angle of the soil.

[0081] Signs related to the action and its effect: [φ p ] is the limit value of the column top inclination angle under the normal working condition SLS; θ p ] is the limit value of the column top torsion angle under the normal working condition SLS; φ f ] is the limit value of the foundation part inclination angle under the normal working condition SLS; θ f ] is the limit value of the foundation part torsion angle under the normal working condition SLS; φ f,r ] is the residual inclination angle limit value of the short pile foundation after the ultimate load condition ULS; φ is the column top inclination angle calculation value; φ f is the inclination angle calculation value of the foundation top surface; φ p is the inclination angle calculation value of the above-ground part of the stand column; θ is the column top torsion angle calculation value; θ f is the torsion angle calculation value of the foundation top surface; θ p is the torsion angle calculation value of the above-ground part of the stand column; H SLS is the horizontal load value under the normal working condition SLS; T SLS is the torsion load value under the normal working condition SLS; M SLS is the bending moment load value under the normal working condition SLS; H ULS is the horizontal load value under the ultimate load condition ULS; T ULS is the torsion load value under the ultimate load condition ULS; M ULS is the bending moment load value under the ultimate load condition ULS; M ] is the cross-section bending resistance of the selected pipe pile model; Q ] is the cross-section shear resistance of the selected pipe pile model; Mp, max is the maximum bending moment of the stand column; Qp, max is the maximum shear force of the stand column ; Mf, max is the maximum bending moment of the foundation; Qf, max is the maximum shear force of the foundation ; φ f is the foundation top inclination angle calculation value; θ f is the foundation top torsion angle calculation value; δ t is the shear displacement between the foundation and the soil interface;δ r is the shear displacement between the foundation and soil interface; δ f is the calculated value of the foundation top displacement (mud surface displacement).

[0082] Geometric dimension related symbols: h is the column height; D p is the outer diameter of the pipe pile; d p is the inner diameter of the pipe pile; I p is the moment of inertia of the pipe pile cross section; I p,p is the polar moment of inertia of the pipe pile cross section; D is the foundation diameter; L is the foundation length; B is the pile cap width; b 1 is the calculated width of the foundation;

[0083] Parameter and coefficient related symbols:

[0084] E p is the elastic modulus of the pipe pile concrete; G p is the shear modulus of the pipe pile concrete; γ c is the coefficient considering the effect of cyclic load; λ r is the residual deformation ratio; γ ht is the coefficient considering the influence of lateral-torsional load coupling effect on foundation deformation; βht is the reduction coefficient considering the lateral-torsional load coupling effect on the bearing capacity of the pipe pile.

[0085] Embodiment

[0086] Combined with the drawings Figure 1 , the present application provides a short pile design method based on deformation and bearing capacity control. The embodiment is described by taking the design of the mirror field column and foundation in a certain tower type solar thermal power station as an example. The implementation steps are as follows:

[0087] Determine the load of each working condition:

[0088] For example, according to the process data, the load of each working condition is respectively H SLS = 3 kN, M SLS = 12.4 kN.m, T SLS = 3.4 kN.m, H ULS= 9.2 kN, M ULS = 21.2 kN.m, T ULS = 14.3 kN.m.

[0089] Determine the column top stiffness control index under each working condition:

[0090] For example, according to the process data, the pile top deformation limit under each working condition is [phi p ]= 1.5 mrad, θ p ]= 1.0 mrad, φ f,r ]= 0.5°.

[0091] Determine whether to use pile cap according to site soil conditions and pile top deformation control requirements:

[0092] For example, according to the survey data, the physical and mechanical properties of the foundation soil are shown in Table 1. According to the research results, the pile cap effect is not obvious in the medium dense round gravel, so the pile cap is not used.

[0093] Table 1 Main physical and mechanical property index results

[0094]

[0095] Select the pile diameter according to the actual situation of the project:

[0096] Reference Figure 3 , for example, according to the load size, deformation requirements and geological data, after preliminary calculation, it is recommended to use PC-500-*-100 pile type, and the reaming diameter is 800 mm.

[0097] Determine the foundation part deformation limit value according to the selected pile diameter, load under normal working condition SLS and column top deformation control requirements:

[0098] For example, according to the process data, h = 3.65 m, then the column deformation above the ground is:

[0099] φp = H SLS h 2 / (2 EpIp )+ M SLS h / ( EpIp ) =0.68 mrad,

[0100] θp = T SLS h / ( GpIp,p=0.155mrad

[0101] but:[ φ f ]=[φ]- φ p =1.5mrad-0.68mard=0.82 mard,

[0102] [ θ f ]=[ θ ]- θ p =1mrad-0.155 mard=0.845 mard,

[0103] On-site pile testing was conducted to determine soil parameters.

[0104] For example, based on field test pile data, a curve showing the variation of the m value with the displacement of the foundation mud surface is plotted. (Reference) Figure 4 , Figure 5 as well as Figure 6 The curves showing the variation of Gs with the shear displacement of the pile-soil contact surface and the variation of the residual deformation ratio with the residual mud surface displacement are used. According to Table 5.3.5-1 of the "Code for Design of Building Pile Foundations" (JGJ 94-2008), the lower limit of the standard value of the ultimate lateral resistance of dense gravelly soil is taken as 135 kPa.

[0105] The initial pile length was determined, and the internal forces and horizontal deformations of the pile under normal working condition SLS and ultimate load condition ULS were calculated respectively using the elastic foundation reaction method:

[0106] For example, based on process data, preliminary selection L =1.85 m The depth of the rotation point is approximately taken as L c =0.667×1.85=1.23m.

[0107] The allowable mud surface displacement under normal operating conditions SLS is [ 0]= L c [ φ f =1.23×0.82=1.01 mm.

[0108] according to Figure 4 When the displacement is 1.01 mm m The value is 175 MN / m 4 Considering that wind load is a long-term or frequent load, the value of m is reduced by 0.4. m= 175 × 0.4 = 70 MN / m 4 .

[0109] According to the elastic foundation reaction method, the allowable value of the displacement of the foundation under the normal working condition SLS is:

[0110] = 0.7 mm, φ = 0.6 mrad, M.max = 25 kN.m;

[0111] The allowable value of the displacement of the foundation under the ultimate load condition ULS is: r = 10.7 mm. L c φ f,r = 1.23 x 8.7 = 10.7 mm.

[0112] According to the fitting of the field test, a = 0.16, and the residual deformation ratio is: = 0.61;

[0113] The limit value of the horizontal residual deformation corresponds to the limit value of the horizontal deformation, which is: = 17.5 mm;

[0114] If the displacement exceeds the range shown in the formula: Figure 4 , the formula in the Technical Specification for Foundation Pit Support can be used:

[0115]

[0116] ϕ — the internal friction angle of the soil (°);

[0117] c — the cohesion of the soil (kPa);

[0118] v b — the horizontal displacement of the foundation (mm);

[0119] The calculation result is m = 12 MN / m 4 . Considering that the wind load is a long-term or frequently occurring load, the value of m is reduced by 0.4, so: m= 12 x 0.4 = 4.8 MN / m 4 .

[0120] According to the elastic foundation reaction method, the allowable value of the displacement of the foundation under the normal working condition SLS is:

[0121] = 25 mm, φ = 22 mrad, M.max = 57 kN.m

[0122] The calculation result of the elastic foundation reaction method is used to check the horizontal deformation of the foundation under the normal working condition SLS:

[0123] For example,​ =0.6 mrad *1.05*1.1=0.693mrad<[ φ f,r ]

[0124] The horizontal deformation then meets the requirements.

[0125] The horizontal residual deformation of the foundation under the ultimate load case (ULS) is verified based on the calculation results of the elastic foundation reaction method:

[0126] For example, =25mm> If the horizontal residual deformation does not meet the requirements, then the horizontal residual deformation will not meet the requirements.

[0127] To verify the horizontal bearing capacity of the foundation under the ultimate limit load case (ULS), for example, it is calculated using the following formula:

[0128]

[0129] have to: L If ≥1.79m>1.85m, then the horizontal bearing capacity meets the requirements.

[0130] Verify the torsional deformation of the foundation under normal operating conditions (SLS); for example, [ 0,t ]=[ θ f ] × 800mm / 2 = 0.34mm; According to Figure 5 The generalized shear modulus can be found. G s Approximately 7.5 MPa. Considering the wind load is a long-term or frequently occurring load, the Gs value is reduced by 0.4. G s =7.5×0.4=3 MPa.

[0131] From the following formula:

[0132] have to: θ = θ 0.28mrad<[ θ f If the torsional deformation meets the requirements, then the torsional deformation is satisfactory.

[0133] To verify the torsional bearing capacity of the foundation under the ultimate limit load case (ULS), for example, it can be calculated using the following formula:

[0134]

[0135] have to: L If ≥0.2m>1.85m, then the torsional bearing capacity meets the requirements.

[0136] If one of the above checking does not meet the requirement, increase the pile length until all meet the requirement,

[0137] In the above checking, the foundation horizontal residual deformation is checked by gradually increasing the foundation length by 0.1 m, and through calculation, when L =2.35 m , the horizontal residual deformation meets the requirement, so L =2.35 m is taken.

[0138] According to the calculation results of the elastic foundation counterforce method, the pile type is determined under the ultimate load working condition (ULS) of the pile body bending moment and the pile crack resistance bending moment, for example, PC-500-A is selected,

[0139] =111kN.m>M.max

[0140] In summary, the selected pile in the example is PC-500-A, L =2.35m.

[0141] The short pile design method proposed in the example meets the process deformation requirement through field engineering pile detection, and the bearing capacity meets the design requirement. Compared with the commonly used ultimate foundation counterforce method, the short pile design method proposed in the example saves about 26% of the engineering quantity under the premise of meeting the bearing capacity and rigidity requirement, and saves about 6% of the engineering quantity under the premise of meeting the residual deformation requirement.

[0142] In summary, the short pile design method based on deformation and bearing capacity control is provided, the relationship between the residual strain ratio and the residual deformation is given, the calculation formula of the influence coefficient of the pile cap on the internal force and deformation of the pile body, the calculation formula of the bearing capacity of the short pile in loess and sand, the calculation formula of the torsional deformation of the short pile in double-layer soil, and the influence of the torsional load and the reciprocating cyclic load on the horizontal deformation of the pile body are considered. The design method considers the horizontal-torsional load coupling, cyclic load, pile cap reinforcement and other conditions, the calculation result is reliable, the precision meets the requirement, and the short pile design of the pile column integrated type can fully meet the requirements of deformation and bearing capacity.

[0143] The above embodiments are only used to illustrate the present application, and are not limited to the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, therefore all equivalent technical solutions also belong to the scope of the present application, and the patent protection scope of the present application should be defined by the claims.

Claims

1. A design method of a pile column integrated short pile based on deformation and bearing capacity control, characterized by, The method comprises the following steps: S01, determining the column top load of the normal working condition SLS and the limit load condition ULS according to the process data; S02, determining the allowable torsion angle, allowable deflection angle or allowable displacement of the column top under the normal working condition SLS and the allowable residual deformation of the column top under the limit load condition ULS according to the process data; S03, according to the site soil conditions and pile top deformation control requirements to determine whether to use pile cap, when the pile cap is set, the pile cap effect is considered, and the load under the normal working condition SLS and the ultimate load condition ULS is reduced; wherein, when the load under the normal working condition SLS and the ultimate load condition ULS is reduced, the reduction factor α m The calculation formula is as follows: where B is the pile cap width; D is the foundation diameter, B B is the pile cap width; S04, preliminarily selecting the pile diameter according to the load size, deformation requirement and geological data of the project; S05, determining the deformation limit value of the foundation part according to the selected pile diameter, load under the normal working condition SLS and column top deformation control requirement; S06, determining the soil parameters through field pile testing; S07, initially determining the pile length, and respectively calculating the internal force and horizontal deformation of the pile under the normal working condition SLS and the limit load condition ULS according to the elastic foundation counterforce method; S08, checking the foundation horizontal deformation under the normal working condition SLS, the foundation horizontal residual deformation under the limit load condition ULS, the foundation horizontal bearing capacity under the limit load condition ULS, the foundation torsion deformation under the normal working condition SLS and the foundation torsion bearing capacity under the limit load condition ULS according to the calculation results of S07; S09, if one of the requirements in S08 is not met, the pile length is increased until all the requirements are met; S10, determining the pile type according to the pile bending moment under the limit load condition ULS and the pile crack-resistant bending moment obtained from S07.

2. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S05, the column top deformation is decomposed into the deformation above the ground and the deformation below the ground, and the calculation formula is as follows: [ φ f ]= [φ]- φ p [ θ f ]= [ θ ]- θ p Wherein, φ f is the basic part inclination limit value under normal working condition SLS, θ f is the basic part torsion angle limit value under normal working condition (SLS), φ p is the inclination calculation value of the ground-above part column, θ p is the torsion angle calculation value of the ground-above part column, is the pile top inclination allowable value under normal working condition SLS, and 3. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S07, the proportional coefficient m of the horizontal base course coefficient used in the horizontal deformation calculation is taken as the field test pile result m δ f The m value corresponding to the horizontal displacement limit value in the curve is multiplied by 0.

4.

4. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S08, the following formula is used to calculate the horizontal deformation to reflect the influence of the cyclic load effect and the horizontal-torsion load coupling effect on the foundation horizontal deformation, and the calculation formula of the foundation horizontal deformation when calculating the cyclic load effect and the horizontal-torsion load coupling effect is as follows: wherein, γ c is the coefficient of cyclic load effect, taken as 1.1; γ t is the coefficient of horizontal-torsional load coupling effect, taken as 1.05, φ f is the calculated value of the inclination of the top surface of the foundation.

5. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S08, the horizontal deformation corresponding to the horizontal residual deformation is obtained through the residual deformation ratio, that is, the checking of the foundation horizontal residual deformation under the limit load condition ULS is converted into the checking of the foundation horizontal deformation under the limit load condition ULS; residual deformation ratio λ r : wherein, is a coefficient related to the soil properties, determined by trial pile, 0.22 for sand, 0.19 for layered soil, and 0.16 for loess when there is no measured data; is the residual deformation value; The calculation of the horizontal deformation limit value corresponding to the horizontal residual deformation limit value is as follows: wherein, is the depth of the point of rotation, taken as 2 L / 3, φ f,r is the limit value of the residual inclination of the short pile foundation after the ultimate load service (ULS).

6. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S10, the foundation horizontal bearing capacity is calculated as follows: Loess: Sandy soil: wherein, h is the column height, D the base diameter, L the base length, the horizontal ultimate bearing capacity, c u the undrained shear strength of the subsoil; K p the passive earth pressure coefficient, γ the weighted average of the unit weight of the soil around the pile.

7. The design method of a short pile based on deformation and bearing capacity control according to claim 1, characterized in that: In S08, the foundation torsion deformation is calculated as follows: For homogeneous soil: For double-layer soil: wherein, L 1 is the thickness of the first layer of soil; L 2 is the depth of the second layer of soil into which the foundation is inserted; G s1 G1 is the shear modulus of the first layer of soil; G s2 G2 = shear modulus of the second layer of soil, R = radius of the foundation, θ θ = calculated value of the top of the column, L L = length of the foundation.

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