CN113175007B - Method for calculating additional force of bridge pile steel sleeve construction - Google Patents
Method for calculating additional force of bridge pile steel sleeve construction Download PDFInfo
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- E02D17/08—Bordering or stiffening the sides of ditches trenches or narrow shafts for foundations
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- E—FIXED CONSTRUCTIONS
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- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
- E02D31/10—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against soil pressure or hydraulic pressure
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
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Abstract
The invention discloses a method for calculating additional force of bridge pile steel sleeve construction, which relates to the technical field of underground engineering and comprises the following steps: establishing a calculation model for steel sleeve construction; according to the calculation model, pile end pressure p is calculated; according to the calculation model, calculating pile side radial pressure q; calculating the vertical frictional resistance f of the pile side according to the calculation model; introducing a soil plug height reduction coefficient zeta according to the pile end pressure p, and calculating a corrected pile end pressure p'; and introducing four-section correction according to the pile side radial pressure q and the pile side vertical frictional resistance f, and calculating the corrected pile side radial pressure q 'and the pile side vertical frictional resistance f'. The method aims to solve the problems that in the related technology, the steel sleeve segmental construction in the actual engineering is neglected when the additional force of the steel sleeve construction is calculated, and the final result and the actual engineering come in and go out due to the influence of the soil squeezing effect within the steel sleeve construction depth range.
Description
Technical Field
The invention relates to the technical field of underground engineering, in particular to a method for calculating additional force of bridge pile steel sleeve construction.
Background
The cast-in-situ bored pile has the characteristics of high construction speed, high bearing capacity, wide application range and the like, so that the cast-in-situ bored pile can be widely applied to large-diameter bridge pile engineering. However, due to the diversity and complexity of the construction process, the quality control is prone to deviation, and construction and quality accidents of the cast-in-situ bored pile occur frequently. Particularly, the construction of large-diameter bridge piles close to an operating subway tunnel easily generates large disturbance on surrounding soil, so that the tunnel generates overlarge deformation, and the operating safety of the subway is seriously threatened if effective engineering measures are not taken. The full casing cast-in-place pile is constructed by organically combining the measures of casing wall protection, advanced hole protection, punching and grabbing hole formation, concrete cast-in-place in the casing and the like, has the advantages of high quality of formed holes and piles, no hole wall collapse, pile breakage, necking risk and the like, and has good applicability in the process of bridge pile close-to-subway tunnel construction in soft soil areas.
The full-rotation casing pipe bored concrete pile construction method is one large diameter bridge pile construction method utilizing full-rotation casing pipe drilling machine to drill through the casing protecting wall and combining with a flushing grab bucket or a rotary drilling machine to take earth to form hole. In the construction process, the full-hole casing pipe retaining wall and the final casing pipe are not pulled out generally, drilling and soil taking and concrete pouring are carried out in the casing pipe, the full-hole casing pipe retaining wall blocks the way of stratum deformation transmission, and the transmission of the pile side additional stress is obviously slowly released. Therefore, the disturbance of the bridge pile construction constructed by adopting the full-length sleeve full-rotation construction method mainly comes from the pressing-in process of the steel sleeve.
In order to further discuss the application of the full casing cast-in-place bridge pile construction process in the adjacent subway tunnel engineering, it is necessary to deeply research the mechanical characteristics of the steel casing construction process, establish a simplified mechanical model, and understand the additional force action of the full casing cast-in-place bridge pile construction process on the existing subway tunnel through stress analysis. However, at present, the analysis of the additional force of steel casing construction does not combine the characteristics of steel casing segmental construction in actual engineering, and the influence of the soil compaction effect in the construction depth range is considered to be deficient. Especially in soft soil areas, because the underground water level is higher, larger excess pore water pressure is generated in the casing pipe construction process, and a certain softening effect exists on the pile-soil interface. Obviously, the pile side additional force in different depth ranges of the steel sleeve construction has obvious nonlinear change rules and is related to the characteristics of the soil around the pile. Therefore, how to obtain the mechanical characteristics of the construction process of the full-casing cast-in-place bridge pile is one of the important points of research.
In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art:
the calculation of the additional force of the steel sleeve construction neglects the characteristics of steel sleeve segmental construction in the actual engineering and the influence of the soil extrusion effect within the construction depth range of the steel sleeve, so that the final result comes in and goes out of the actual engineering.
Disclosure of Invention
The invention aims to provide a method for calculating the additional force of bridge pile steel sleeve construction, which aims to solve the problems that in the related technology, the steel sleeve segmental construction in actual engineering is neglected when the additional force of the steel sleeve construction is calculated, and the influence of the soil squeezing effect in the steel sleeve construction depth range causes the final result to come in and go out of the actual engineering.
According to the embodiment of the application, the method for calculating the additional force of the bridge pile steel sleeve construction comprises the following steps:
establishing a calculation model of steel sleeve construction;
according to the calculation model, pile end pressure p is calculated;
according to the calculation model, calculating pile side radial pressure q;
calculating the vertical frictional resistance f of the pile side according to the calculation model;
introducing a soil plug height reduction coefficient zeta according to the pile end pressure, and calculating a corrected pile end pressure p';
and introducing four-section correction according to the pile side radial pressure and the pile side vertical frictional resistance, and calculating the corrected pile side radial pressure q 'and the pile side vertical frictional resistance f'.
Further, establishing a calculation model of steel casing construction, comprising:
and establishing a coordinate system by taking the circumferential center of the pile top of the bridge pile as a coordinate origin, wherein the bridge pile is perpendicular to the xoy plane, and constructing along the positive direction of the z axis to obtain a calculation model for steel sleeve construction.
Further, calculating the pile tip pressure p comprises:
calculating the pile end pressure when the soil plug in the steel sleeve spirally slides upwards;
calculating pile end pressure when the soil plug in the steel sleeve slides vertically upwards;
and selecting the pile end pressure calculation formula according to different construction processes, and calculating the pile end pressure p.
Further, calculating the pile tip pressure p comprises:
(1) Calculating the pile end pressure when the soil plug in the steel sleeve spirally slides upwards;
when the soil body is entered by spinning the steel sleeve and before annular shearing damage occurs, the soil plug in the steel sleeve slides upwards relative to the steel sleeve in a spiral mode, and at the moment, the calculation formula of the pile end pressure is as follows:
wherein t is the wall thickness (m) of the steel sleeve; e is the elastic modulus (MPa) of the soil body; d s Is the sum (m) of the diameter of the bridge pile and the wall thickness of the steel sleeve, d s D + t, d is the diameter (m) of the bridge pile; n is the ratio of the relative tangential velocity and the vertical velocity of the inner wall of the steel sleeve and the soil plug; a is the cross-sectional area (m) of the soil plug 2 ) (ii) a v is the poisson's ratio of the soil mass; c. C a The cohesive force (kN/m) of the soil plug and the inner wall of the steel sleeve 2 )，
The friction angle (DEG) between the soil plug and the inner wall of the steel sleeve and the interfacial cohesion force c a Angle of friction with interface
Should be based on cohesive force c and internal friction angle of surrounding soil
Is appropriately reduced, c a ＝R 0 c，
R 0 Is a reduction factor; u is the perimeter (m) of the inner wall of the steel sleeve; gamma is the gravity of the soil body (kN/m) 3 )；z 0 The height (m) of the soil body at the bottommost layer of the soil plug; p is a radical of 1 Is the top stress (kN/m) of the soil body at the bottommost layer of the soil plug 2 )；
(2) Calculating pile end pressure when the soil plug in the steel sleeve slides vertically upwards;
when the soil body is entered by spinning the steel sleeve and after annular shearing damage or entered by vertical static pressure steel sleeve, the soil plug in the steel sleeve slides vertically upwards relative to the steel sleeve, at this moment, the calculation formula of the pile end pressure is:
(3) And selecting the pile end pressure calculation formula according to different construction processes, and calculating the pile end pressure p.
Further, calculating a pile-side radial pressure q, comprising:
the calculation formula of the pile side radial pressure in the steel sleeve pressing-in process is as follows:
q＝K 0 γh (5)
in the formula, K 0 Is the static lateral pressure coefficient, K, of the pile lateral soil body 0 = v/(1-v); h is the depth (m) of the soil body.
Further, the step of calculating the vertical frictional resistance f of the pile side comprises the following steps:
the calculation formula of the pile side vertical frictional resistance in the steel sleeve pressing-in process is as follows:
f＝K 0 γh·tanδ (6)
in the formula, δ is an external friction angle (°) of the steel casing and the soil body.
Further, the step of calculating the corrected pile tip pressure p' by introducing the soil plug height reduction coefficient zeta comprises the following steps:
calculating a soil plug height reduction coefficient zeta;
and calculating the corrected pile end pressure p' according to the soil plug height reduction coefficient zeta.
Further, the step of calculating the corrected pile tip pressure p' by introducing the soil plug height reduction coefficient zeta comprises the following steps:
(1) Calculating a soil plug height reduction coefficient zeta;
simplifying the process of steel sleeve segmental construction, assuming that the height of the soil plug during the construction of each segment of the sleeve is a certain value and is related to the segmental construction height of the sleeve, and establishing the height z of the soil plug s Segmental construction height z with steel sleeve t The relationship between them is:
z s ＝z t ·ζ (7)
(2) Calculating corrected pile end pressure p' according to the soil plug height reduction coefficient zeta;
according to the height z of the soil plug s The height z of the soil body at the bottommost layer of the soil plug in the pile end pressure calculation formula can be calculated 0 The corrected pile tip pressure p' is further calculated.
Further, calculating a corrected pile side radial pressure q 'and a pile side vertical frictional resistance f' includes:
calculating the height of each section corrected by the four sections;
and calculating the corrected pile side radial pressure q 'and the pile side vertical frictional resistance f' according to the heights of all the sections.
Further, calculating a corrected pile side radial pressure q 'and a pile side vertical frictional resistance f' includes:
(1) Calculating the height of each section corrected by the four sections;
dividing the range of the penetration depth of steel sleeve construction in a soft soil area into an upper vacuum pressure section H according to the stratum distribution condition, the strong and weak influence of the soil squeezing effect and the exerting degree of the circumferential frictional resistance of the pile 1 Middle pressure reduction section H 2 Lower soil-rock soft-hard alternating section H 3 And a bottom soil-squeezing pressure section H 4 Four parts in total;
(2) And calculating the corrected pile side radial pressure q 'and the pile side vertical frictional resistance f' according to the heights of all the sections.
In the formula, beta i Is H 2 The softening coefficient of the weakening area of the soil squeezing effect in the middle of the section is similar to the residual frictional resistance f of the pile-soil interface sr And ultimate frictional resistance f u The ratio of (A) to (B); eta i Is H 4 The soil squeezing effect strengthening coefficient of the soil plug area at the bottom of the section.
The technical scheme provided by the embodiment of the application can have the following beneficial effects:
the invention provides a method for calculating additional force for bridge pile steel sleeve construction, which is characterized in that the mechanical characteristics of the steel sleeve construction process are simplified and analyzed, the sleeve segmental construction characteristics and the influence of a soil squeezing effect are considered, a soil plug height reduction coefficient and four-section correction are introduced, and a correction calculation formula of each additional force for steel sleeve construction is provided, so that the method is more in line with the actual construction characteristics and has more engineering applicability. The method has important theoretical significance for further determining the characteristics of additional force of steel sleeve construction and fully knowing the construction influence of the full-sleeve cast-in-place bridge pile, and provides a means for evaluating in advance for the safe construction of subsequent engineering. The calculation method provided by the invention is simple and clear, the calculation is quick and convenient, the calculation can be carried out by using numerical calculation software such as MATLAB (matrix laboratory), the application range is wide, and the method can be suitable for making formula adjustment under different geological conditions and different construction process characteristics. The method optimizes and perfects the calculation method of the steel sleeve construction additional force, provides a quick and effective theoretical means for the influence analysis of the steel sleeve construction, and also lays a theoretical foundation for the influence evaluation of the full-casing cast-in-place bridge pile construction adjacent to the subway tunnel.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.
Fig. 1 is a flow chart illustrating a method for calculating additional force for steel casing construction of a bridge pile according to an exemplary embodiment.
FIG. 2 is a schematic diagram of a computational model shown in accordance with an exemplary embodiment, wherein (a) is a three-dimensional schematic diagram of the computational model and (b) is a two-dimensional schematic diagram of the computational model.
FIG. 3 is a schematic illustration of a steel casing construction additional force profile, according to an exemplary embodiment.
Detailed Description
The invention is further described below with reference to examples and figures. The following examples are carried out on the premise of the technical solution of the present invention, and the description of the examples is only for helping understanding of the present invention, but not for limiting the present invention. It will be apparent to those skilled in the relevant art that various modifications and variations can be made in the present invention without departing from the principles of the invention. Such modifications and variations are intended to fall within the scope of the appended claims.
Fig. 1 is a flowchart illustrating a method of calculating additional force for steel casing construction of a bridge pile according to an exemplary embodiment, and referring to fig. 1, the method may include the steps of:
s11, establishing a calculation model of steel sleeve construction;
step S12, calculating pile end pressure p according to the calculation model;
step S13, calculating pile side radial pressure q according to the calculation model;
step S14, calculating the vertical frictional resistance f of the pile side according to the calculation model;
step S15, according to the pile end pressure, introducing a soil plug height reduction coefficient zeta, and calculating corrected pile end pressure p';
and S16, introducing four-section correction according to the pile side radial pressure and the pile side vertical frictional resistance, and calculating corrected pile side radial pressure q 'and pile side vertical frictional resistance f'.
According to the embodiment, the mechanical characteristics of the steel sleeve construction process are simplified and analyzed, the sleeve segmental construction characteristics and the soil squeezing effect influence are considered, the soil plug height reduction coefficient and the four-section correction are introduced, the correction calculation formula of each additional force of the steel sleeve construction is provided, the actual construction characteristics are better met, and the engineering applicability is better. The method has important theoretical significance for further determining the characteristics of additional force of steel sleeve construction and fully knowing the construction influence of the full-sleeve cast-in-place bridge pile, and provides a means for evaluating in advance for the safe construction of subsequent engineering. The calculation method provided by the invention is simple and clear, the calculation is quick and convenient, the calculation can be carried out by using numerical calculation software such as MATLAB (matrix laboratory), the application range is wide, and the method can be suitable for making formula adjustment under different geological conditions and different construction process characteristics. The method optimizes and perfects the calculation method of the steel sleeve construction additional force, provides a quick and effective theoretical means for the influence analysis of the steel sleeve construction, and also lays a theoretical foundation for the influence evaluation of the full-casing cast-in-place bridge pile construction adjacent to the subway tunnel.
The method provided by the embodiment of the invention is explained in detail by taking a certain bridge test pile construction project in Hangzhou city as an example.
In the specific implementation of the step S11, a calculation model of steel sleeve construction is established;
specifically, a coordinate system is established by taking the circumferential center of the pile top of the bridge pile as the origin of coordinates, as shown in fig. 2, the bridge pile is perpendicular to the xoy plane, and construction is performed along the z-axis in the forward direction, so that a calculation model for steel sleeve construction is obtained. In the calculation model, the acting force of steel sleeve construction on the surrounding soil body is mainly pile end pressure p, pile side radial pressure q and pile side vertical frictional resistance f. In the calculation model, the diameter of the bridge pile is d, and the thickness of the steel sleeve is t, r s = d/2+t, steel casing length H.
In a specific implementation of step S12, the pile tip pressure p is calculated from the calculation model, which may include the following sub-steps:
(1) Calculating the pile end pressure when the soil plug in the steel sleeve spirally slides upwards;
specifically, when the steel sleeve is spun to enter the soil body and before annular shearing damage occurs, the soil plug in the steel sleeve slides upwards relative to the steel sleeve in a spiral mode, and at the moment, the calculation formula of the pile end pressure is as follows:
wherein t is the wall thickness (m) of the steel sleeve; e is the modulus of elasticity (MPa) of the soil, E =2.5E in this example s ，E s The compressive modulus (MPa) of the soil body; d s Is the sum (m) of the diameter of the bridge pile and the wall thickness of the steel sleeve, d s D + t, d is the diameter (m) of the bridge pile; n is the ratio of the relative tangential velocity and the vertical velocity of the inner wall of the steel sleeve and the soil plug, and n =1 in the embodiment; a is the cross-sectional area (m) of the soil plug 2 ) (ii) a v is the poisson's ratio of the soil mass; c. C a The cohesive force (kN/m) of the soil plug and the inner wall of the steel sleeve 2 )，
The friction angle (DEG), c, of the soil plug and the inner wall of the steel sleeve a ＝R 0 c，
Reduction factor R in the present embodiment 0 =0.7; u is the perimeter (m) of the inner wall of the steel sleeve; gamma is the gravity of the soil body (kN/m) 3 )；z 0 The height (m) of the soil body at the bottommost layer of the soil plug; p is a radical of 1 Is the top stress (kN/m) of the soil body at the bottommost layer of the soil plug 2 )。
(2) Calculating pile end pressure when the soil plug in the steel sleeve slides vertically upwards;
specifically, when the soil body is entered by spinning the steel sleeve and after the annular shear failure occurs or the soil body is entered by using the vertical static pressure steel sleeve, the soil plug in the steel sleeve vertically slides upwards relative to the steel sleeve, and at the moment, the calculation formula of the pile end pressure is as follows:
(3) And selecting the pile end pressure calculation formula according to different construction processes, and calculating the pile end pressure p.
In the specific implementation of step S13, a pile-side radial pressure q is calculated according to the calculation model;
specifically, the calculation formula of the pile side radial pressure in the steel sleeve pressing-in process is as follows:
q＝K 0 γh (9)
in the formula, K 0 Is the static lateral pressure coefficient, K, of the pile-side soil body 0 = v/(1-v); h is the depth (m) of the soil body.
In the specific implementation of the step S14, a pile side vertical frictional resistance f is calculated according to the calculation model;
specifically, the calculation formula of the pile side vertical frictional resistance in the steel sleeve pressing-in process is as follows:
f＝K 0 γh·tanδ (17)
in the formula, δ is an external friction angle (°) between the steel casing and the soil body, and in this embodiment, values of the external friction angles of the clay, sand, clay-containing grit, and smooth steel interface are 9.0 °, 24.0 ° and 9.5 °, respectively.
In the specific implementation of step S15, the step of calculating the corrected pile tip pressure p' by introducing the soil plug height reduction coefficient ζ according to the pile tip pressure may include the following sub-steps:
(1) Calculating a soil plug height reduction coefficient zeta;
specifically, in the construction process of the steel sleeve, the drilling machine continuously excavates out soil in the sleeve, and the height of the soil plug in the sleeve is always maintained within a certain range. Simplifying the process of steel sleeve segmental construction, assuming that the height of the soil plug during the construction of each segment of the sleeve is a certain value and is related to the segmental construction height of the sleeve, and establishing the height z of the soil plug s Segmental construction height z with steel sleeve t The relationship between them is:
z s ＝z t ·ζ (7)
in the formula, the value range of the soil plug height reduction coefficient ζ in this example is 0.60.
(2) And calculating the corrected pile end pressure p' according to the soil plug height reduction coefficient zeta.
In particular, according to the soil plug height z s The height z of the soil body at the bottommost layer of the soil plug in the pile end pressure calculation formula can be calculated 0 The corrected pile tip pressure p' is further calculated.
In the specific implementation of step S16, introducing four-segment correction according to the pile-side radial pressure and the pile-side vertical frictional resistance, and calculating the corrected pile-side radial pressure q 'and the pile-side vertical frictional resistance f' may include the following sub-steps:
(1) Calculating the height of each section corrected by the four sections;
specifically, according to the stratum distribution condition, the influence of the soil squeezing effect and the exertion degree of the friction resistance around the pile, the soil penetration depth range of the steel sleeve construction in the soft soil area is divided into four parts, namely an upper part, a middle part, a lower part and a bottom part. Wherein H represents the length of the bridge pile or the length of the steel sleeve, H 1 、H 2 、H 3 And H 4 Respectively, representing different segment heights.
1)H 1 The section is an upper vacuum pressure section (also called a near-empty load section): as the phenomena of casing pipe connection deviation non-perpendicularity, casing pipe intermittent rotation and repeated pressing and lifting of the casing pipe during initial drilling exist in the construction process of the steel casing pipe, a longer vacuum pressure section is formed between soil bodies adjacent to the ground surface and the casing pipe, the fact that the inner casing pipe of the section is not in contact with surrounding soil bodies is approximately considered, and pile side radial pressure and pile side vertical frictional resistance do not exist. Example H of the present invention 1 The value is 0.10H.
2)H 2 The section is a middle pressure reduction section (also called a softening section): because the engineering middle stratum is generally a water-bearing stratum, the seepage effect of underground water is easily caused in the pressing-in process of the sleeve and the excess pore water pressure generated by construction disturbance soil bodies, when the relative displacement of pile soil exceeds a limit value, the pile-soil interface has a softening effect, and the stratum pressure in the section is relatively reduced. It should be noted that: except for soil bodies with higher water content such as soft clay, such as sandy soil, round gravel, corner gravel and the like, the softening effect of the pile-soil interface is not obvious, and the soft clay can not be considered in calculation. Example H of the present invention 2 Taking the value of 0.30H.
3)H 3 Segment is as followsPart soil-rock soft and hard alternating section (also called stable section): the construction of the large-diameter full-length sleeve full-rotation cast-in-place pile in a soft soil area requires entering a weathered rock stratum, the steel sleeve undergoes a stratum alternation process of hard soil and rock at the lower part of upper soft soil in the pressing-in process, at the moment, the pile body is overall stable, and the pressure and the frictional resistance of the soil body around the pile are obviously greater than those of the middle stratum. Example H of the present invention 3 Taking the value of 0.50H.
4)H 4 The section is a bottom soil-squeezing pressure section (also called a soil plug section): because the soil body in the sleeve is continuously taken out in the pressing-in process of the steel sleeve, the height of a soil plug existing in the sleeve shoe at the bottom of the pile is generally maintained in a certain range, the soil body at the sleeve shoe is deformed by lateral extrusion, the outward extrusion effect is obvious, and the lateral pressure and the vertical frictional resistance of the soil body around the pile are increased. However, plastic deformation of the soil surrounding the casing shoe simultaneously reduces the strength of the soil, resulting in only a limited increase in the pressure on the pile side of the section. Example H of the present invention 4 Taking the value of 0.10H.
(2) And calculating the corrected pile side radial pressure q 'and the pile side vertical frictional resistance f' according to the heights of all the sections.
Specifically, the calculation formula after the section correction is performed on the pile side radial pressure q and the pile side vertical frictional resistance f is as follows:
in the formula, beta i Is H 2 The softening coefficient of the weakening area of the soil squeezing effect in the middle of the section is similar to the residual frictional resistance f of the pile-soil interface sr And ultimate frictional resistance f u The value of the ratio (A) in the embodiment of the invention is 0.66; eta i Is H 4 The soil compaction effect strengthening coefficient of the soil plug area at the bottom of the section is 1.02 in the embodiment of the invention.
In this embodiment, the foundation soil of the engineering field can be divided into 7 engineering fields according to different cause types and different physical and mechanical propertiesThe geological formation is subdivided into 16 sub-layers, and the distribution and physical and mechanical characteristic parameters of each geotechnical layer are shown in table 1. The engineering design and construction scheme is as follows: the engineering of the embodiment adopts the full-length sleeve full-rotation cast-in-place bridge pile construction, the length of the bridge pile or the length of a steel sleeve H =70.0m, the diameter of the bridge pile d =1.5m, the thickness t =30.0mm of the steel sleeve, and the segmental construction height z of the steel sleeve t ＝8.0m。
Table 1 engineering geological parameter table of the embodiment of the present invention
Based on engineering geological parameters and main engineering calculation parameters, according to the correction formula of the pile end pressure p, the pile side radial pressure q and the pile side vertical frictional resistance f of the steel sleeve construction additional force, calculating through MATLAB numerical calculation software, and obtaining the rule that the numerical value of each additional force changes along with the construction depth of the steel sleeve.
In general, the method for calculating the additional force for the steel sleeve construction of the bridge pile comprehensively considers the characteristics of engineering construction and geological conditions, has better engineering applicability, can effectively predict the disturbance influence of the steel sleeve construction, and provides a theoretical basis for engineering risk evaluation and safety prevention and control of the construction of the full-sleeve cast-in-place bridge pile adjacent to the subway tunnel.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A method for calculating additional force of bridge pile steel sleeve construction is characterized by comprising the following steps:
establishing a calculation model for steel sleeve construction;
according to the calculation model, the pile end pressure is calculated
；
According to the calculation model, the radial pressure of the pile side is calculated
；
According to the calculation model, the vertical frictional resistance of the pile side is calculated
；
According to the pile tip pressure
Introducing the reduction coefficient of the soil plug height
Calculating corrected pile tip pressure
；
According to the pile side radial pressure
Vertical frictional resistance of pile side
Introducing four-segment correction, calculating corrected pile-side radial pressure
Vertical frictional resistance of pile side
；
The height reduction coefficient of the introduced soil plug
Calculating corrected pile tip pressure
The method comprises the following steps:
calculating the reduction coefficient of the soil plug height
；
Simplifying the process of steel sleeve segmental construction, assuming that the height of the soil plug during the construction of each segment of the sleeve is a certain value and is related to the segmental construction height of the sleeve, and establishing the height of the soil plug
Segmental construction height with steel sleevez t The relationship between them is:
according to the height reduction coefficient of the soil plug
Calculating corrected pile tip pressure
；
According to the height of the soil plug
The height of the soil body at the bottommost layer of the soil plug in the pile end pressure calculation formula can be calculated
Further calculating the corrected pile tip pressure
；
Said calculating a corrected pile side radial pressure
Vertical frictional resistance of pile side
The method comprises the following steps:
calculating the height of each section corrected by the four sections;
calculating a corrected pile-side radial pressure from the segment heights
Vertical frictional resistance of pile side
；
Calculating a corrected pile side radial pressure
Vertical frictional resistance of pile side
The method comprises the following steps:
calculating the height of each section corrected by the four sections;
dividing the range of the penetration depth of steel sleeve construction in a soft soil area into an upper vacuum pressure section according to the stratum distribution condition, the strong and weak influence of the soil squeezing effect and the exerting degree of the circumferential frictional resistance of the pile
Middle pressure reduction section
Lower soil-rock soft-hard alternating section
And bottom soil-squeezing pressure section
Four parts in total;
calculating a corrected pile side radial pressure from said each segment height
Vertical frictional resistance of pile side
；
In the formula (I), the compound is shown in the specification,
is composed of
The softening coefficient of the weakening area of the soil squeezing effect in the middle of the section is similar to the residual frictional resistance of the pile-soil interface
Limit frictional resistance
The ratio of (a) to (b);
is composed of
The soil squeezing effect strengthening coefficient of the soil plug area at the bottom of the section.
2. The method of claim 1, wherein building a computational model of steel casing construction comprises:
establishing a coordinate system by taking the circumferential center of the pile top of the bridge pile as the origin of coordinates, wherein the bridge pile is perpendicular to the bridge pile
Plane along
And (5) performing forward construction on the shaft to obtain a calculation model of steel sleeve construction.
3. The method of claim 1, wherein pile tip pressure is calculated
The method comprises the following steps:
calculating the pile end pressure when the soil plug in the steel sleeve spirally slides upwards;
calculating pile end pressure when the soil plug in the steel sleeve slides vertically upwards;
selecting the pile end pressure calculation formula according to different construction processes to calculate the pile end pressure
。
4. The method of claim 1, wherein pile tip pressure is calculated
The method comprises the following steps:
(1) Calculating the pile end pressure when the soil plug in the steel sleeve spirally slides upwards;
when the mode of spinning the steel sleeve pipe is adopted to enter the soil body and before annular shearing damage occurs, the soil plug in the steel sleeve pipe slides upwards relative to the steel sleeve pipe in a spiral mode, and at the moment, the calculation formula of the pile end pressure is as follows:
in the formula (I), the compound is shown in the specification,
wall thickness (m) of the steel casing;
the elastic modulus (MPa) of the soil body;
is the sum (m) of the diameter of the bridge pile and the wall thickness of the steel sleeve,
，
is the diameter (m) of the bridge pile;
the ratio of the relative tangential velocity and the vertical velocity of the inner wall of the steel sleeve and the soil plug is obtained;
is the cross-sectional area (m) of the soil plug 2 )；
The poisson ratio of the soil body;
the cohesive force (kN/m) of the soil plug and the inner wall of the steel sleeve 2 )，
The friction angle (DEG) of the soil plug and the inner wall of the steel sleeve and the interfacial cohesion
Angle of friction with interface
Should be based on cohesive forces of the surrounding soil mass
And angle of internal friction
The proper reduction is carried out, and the thickness of the steel plate is reduced,
is a reduction factor;
is the circumference (m) of the inner wall of the steel sleeve;
is the gravity of the soil body (kN/m) 3 )；
The height (m) of the soil body at the bottommost layer of the soil plug;
is the bottom of the soil plugTop stress of the subsoil (kN/m) 2 )；
(2) Calculating pile end pressure when the soil plug in the steel sleeve slides vertically upwards;
when the soil body is entered by spinning the steel sleeve and after annular shearing damage or entered by vertical static pressure steel sleeve, the soil plug in the steel sleeve slides vertically upwards relative to the steel sleeve, at this moment, the calculation formula of the pile end pressure is:
(3) Selecting the pile end pressure calculation formula according to different construction processes to calculate the pile end pressure
。
5. The method of claim 4, wherein pile side radial pressure is calculated
The method comprises the following steps:
the calculation formula of the pile side radial pressure in the steel sleeve pressing-in process is as follows:
in the formula (I), the compound is shown in the specification,
is the static side pressure coefficient of the soil body on the pile side,
；
the depth (m) of the soil body.
6. The method of claim 5, wherein pile side vertical frictional resistance is calculated
The method comprises the following steps:
the calculation formula of the pile side vertical frictional resistance in the steel sleeve pressing-in process is as follows:
in the formula (I), the compound is shown in the specification,
the external friction angle (°) of the steel casing and the soil body.
7. The method of claim 1, wherein the soil plug height reduction factor is introduced
Calculating corrected pile tip pressure
The method comprises the following steps:
calculating the reduction coefficient of the soil plug height
；
According to the height reduction coefficient of the soil plug
Calculating corrected pile tip pressure
。
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