CN109284538B - Method for reducing length of bridge slope pile foundation - Google Patents

Method for reducing length of bridge slope pile foundation Download PDF

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CN109284538B
CN109284538B CN201810997053.3A CN201810997053A CN109284538B CN 109284538 B CN109284538 B CN 109284538B CN 201810997053 A CN201810997053 A CN 201810997053A CN 109284538 B CN109284538 B CN 109284538B
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pile foundation
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CN109284538A (en
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康俊涛
林光毅
张学强
刘开
齐凯凯
邵光强
秦世强
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Wuhan University of Technology WUT
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Abstract

The invention discloses a method for reducing the length of a slope pile foundation, which comprises the following steps: firstly, specific parameters of a soil layer at the position of a pile foundation are investigated, then numerical models under different slopes are established according to the parameters, and after the numerical models are subjected to operational analysis, the side frictional resistance of each pile is extracted; determining the reduction length of the slope pile under each slope according to the distribution mode of the side friction resistance; and finally, fitting the relation between the reduced length and the gradient, so that the use of similar items is facilitated. The method provides basis for designing the slope pile foundation, improves the safety of pile foundation design, and has higher engineering application value.

Description

Bridge slope pile foundation length reduction method
Technical Field
The invention relates to a bridge design technology, in particular to a method for reducing the length of a bridge slope pile foundation.
Background
The pile on the slope and the flat slope pile are different in stress mode, so that the bearing capacity of the slope pile is reduced relative to a common pile with the same soil penetration depth, however, the concrete reduction mode of the slope pile is not mentioned by each standard at the current stage, and in the actual design, the slope pile is either too conservative or has certain potential safety hazard.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for reducing the length of a bridge slope pile foundation, aiming at the defects in the prior art, the method can effectively reduce the length of the pile foundation, so that the reduced pile foundation is stronger and more reasonable in safety reserve, and has certain guiding significance for the design of the slope pile foundation at the present stage.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for reducing the length of a bridge slope pile foundation comprises the following steps:
1) Determining specific parameters of a slope pile foundation soil layer to be processed, including an internal friction angle, cohesive force, elastic modulus and Poisson ratio;
2) Establishing a series of numerical models according to the obtained soil layer parameters and different gradients; the range of the gradient is 0-60 degrees, and the gradient grade difference is 10 degrees;
3) Carrying out operation analysis on the numerical model, and extracting the pile side frictional resistance of each pile;
4) Analyzing the distribution condition of the side friction resistance of each pile, taking the side friction resistance as an abscissa and the pile foundation burial depth as an ordinate, and determining the starting point of the side friction resistance at each slope, namely the position of the depth to be reduced;
5) Summarizing the slope degree and the depth to be reduced of each pile, and drawing a related graph by taking the slope degree as a horizontal coordinate and the depth to be reduced as a vertical coordinate;
6) And fitting the graph into a specific formula, and checking the pile length by using a standard related formula after obtaining the reduced depth.
According to the scheme, the method for determining the starting point of the side friction resistance in the step 4) comprises the following steps: dividing the pile foundation into a unit every 2m, dividing the pile foundation into a plurality of units, wherein two ends of each unit are nodes, and when the slope of the side friction resistance distribution diagram before two adjacent nodes is more than 40 degrees, the node which starts to be more than 40 degrees is used as a side friction resistance starting point.
According to the scheme, the numerical model in the step 2) is a finite element model or a finite difference model.
The invention has the following beneficial effects:
firstly, the influence of the slope on the length of the bridge pile foundation is considered, and the method is more accurate and effective compared with a method without considering the influence.
Secondly, the method has good compatibility, can be directly butted with a standard calculation method, and only increases the invalid soil range for the standard method.
Thirdly, the numerical simulation establishing method and the data output of the invention can adopt a command stream mode, the modeling is simple, the change is convenient, and the calculation efficiency is high.
Drawings
The invention will be further described with reference to the following drawings and examples, in which:
FIG. 1 is a flow chart of a method of an embodiment of the present invention;
FIG. 2 is a diagram of an exemplary numerical model of an embodiment of the present invention;
FIG. 3 is a pile side friction profile of an embodiment of the present invention;
FIG. 4 is a reduced length trend graph of an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
As shown in fig. 1, the method for determining the length reduction of the slope pile foundation comprises the following steps:
1) Determining specific parameters of a slope pile foundation soil layer to be processed, including an internal friction angle, cohesive force, elastic modulus and Poisson ratio;
this example is based on certain geological survey data, and the rock formation is strongly weathered rock, and the basic parameters are set as follows:
internal friction angle =25 °;
cohesion =2400kPa;
elastic modulus =32.5GPa;
poisson ratio =0.27;
severe weight =25kN/m 3 。
2) According to the obtained soil layer parameters and different gradients, establishing a series of numerical models; the range of the gradient is 0-60 degrees, and the gradient grade difference is 10 degrees; the numerical model is a finite element model or a finite difference model; as shown in FIG. 2;
establishing a series of numerical models according to the obtained soil layer parameters and different gradients; the gradient range is 0-60 degrees, the gradient range is 10 degrees, namely seven models of 0, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees and 60 degrees are established;
3) Carrying out operation analysis on the numerical model, and extracting the pile side frictional resistance of each pile;
4) Analyzing the distribution condition of the side friction resistance of each pile, and determining the starting point (namely the position needing to be reduced in depth) of the side friction resistance at each slope by taking the side friction resistance as an abscissa and taking the pile foundation burial depth as an ordinate; as shown in fig. 3, during modeling, each 2m unit of the pile foundation is divided into a plurality of units, two ends of each unit are nodes (if the pile foundation is longer, the number of units can be increased), and when the slope before two adjacent nodes in the side friction resistance distribution diagram is greater than 40 degrees, the node when the slope is greater than 40 degrees is used as the side friction resistance starting point.
5) And summarizing the slope degree and the depth to be reduced of each pile, drawing a relevant graph by taking the slope degree as a horizontal coordinate and the depth to be reduced as a vertical coordinate, and fitting. As shown in fig. 4, it can be seen that the side friction force acting points increase with increasing burial depth, and the increasing tendency can be regarded as substantially linear.
6) And fitting the graph into a specific formula, and checking the pile length by using a standard related formula after the reduction depth is obtained.
The fitting graph is rewritten into a specific formula, so that the practical design and use are facilitated. The concrete form is as follows:
Figure BDA0001782100890000051
in the formula, L re Representing the depreciation burial depth, in units of diameter (d); s represents the gradient in degrees (°).
When the method is used specifically, if a 45-degree slope is provided, and the formula is substituted, the reduction burial depth can be obtained as follows: l is re =2/5 × 45-8=10m. The side friction resistance above the depth is not considered and is not included in the calculation.
It will be appreciated that modifications and variations are possible to those skilled in the art in light of the above teachings, and it is intended to cover all such modifications and variations as fall within the scope of the appended claims.

Claims (2)

1. A method for reducing the length of a bridge slope pile foundation is characterized by comprising the following steps:
1) Determining specific parameters of a slope pile foundation soil layer to be processed, including an internal friction angle, cohesive force, elastic modulus and Poisson ratio;
2) Establishing a series of numerical models according to the obtained soil layer parameters and different gradients; the range of the gradient is 0-60 degrees, and the gradient grade difference is 10 degrees;
3) Carrying out operation analysis on the numerical model, and extracting the pile side frictional resistance of each pile;
4) Analyzing the distribution condition of the side friction resistance of each pile, taking the side friction resistance as an abscissa and the pile foundation burial depth as an ordinate, and determining the starting point of the side friction resistance at each slope, namely the position of the depth to be reduced;
the determination method of the side friction resistance starting exertion point in the step 4) is as follows: dividing the pile foundation into a unit every 2m, dividing the pile foundation into a plurality of units, wherein two ends of each unit are nodes, and when the slope of the side frictional resistance distribution diagram before two adjacent nodes is more than 40 degrees, the node which starts to be more than 40 degrees is used as a side frictional resistance starting point;
5) Summarizing the slope degree and the depth to be reduced of each pile, and drawing a related graph by taking the slope degree as a horizontal coordinate and the depth to be reduced as a vertical coordinate;
6) And fitting the graph into a specific formula, and checking the pile length by using a standard related formula after the reduction depth is obtained.
2. The method for reducing the length of the bridge slope pile foundation according to claim 1, wherein the numerical model in the step 2) is a finite element model or a finite difference model.
CN201810997053.3A 2018-08-29 2018-08-29 Method for reducing length of bridge slope pile foundation Active CN109284538B (en)

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