Journal of Jilin University(Engineering and Technology Edition) ›› 2020, Vol. 50 ›› Issue (2): 621-630.doi: 10.13229/j.cnki.jdxbgxb20181130

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Applicability analysis of two dimensional modelingmethods for wide embankment composite foundation in high speed railway stations

Yang LI1,2(),Lian-jun WANG1,2()   

  1. 1.School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
    2.Beijing Key Laboratory of Track Engineering, Beijing Jiaotong University, Beijing 100044, China
  • Received:2018-11-13 Online:2020-03-01 Published:2020-03-08
  • Contact: Lian-jun WANG E-mail:liyang6@bjtu.edu.cn;ljwang@bjtu.edu.cn

Abstract:

Three dimensional (3D) modeling of some complex pile composite foundations in high speed railway can be very complicated and time-consuming. So it is a common way to simplify 3D models into two dimensional (2D) models in current research, however, the applicability of different 2D modeling methods remains unclear. In this research, taking Ji'nanxi station in Beijng-Shanghai high speed railway as an example, five different 2D models are established to study their applicability by comparing the results of 2D models with that of 3D models and site measurement data. The study shows that 2D models can provide acceptable results for the development of settlements, stress of pile and soil, as well as lateral displacements. The method which remains the same elastic module and area replacement ratio yields the best results out of all 2D models. But a 3D model is necessary for the generation and dissipation of excess pore water pressures in foundation and bending moments of pile close to the toe of embankment, because 2D models give incorrect results.

Key words: highway and railway engineering, composite foundation, two dimensional model, settlement

CLC Number: 

  • U213.1

Fig.1

Foundation treatment and monitoring scheme"

Fig.2

Construction sequence of embankment"

Fig.3

Modeling of composite foundation in two dimension"

Fig.4

Top view of composite foundation unit model"

Table 1

Parameters of continuous wall"

方法原桩型为CFG桩原桩型为PHC桩
dw/mEw/GPadw/mEw/GPa
恒定参数法0.5025.500.0839.20
等弹性模量法0.1325.500.0239.20
等桩径法0.506.690.083.17
等抗压刚度法0.503.770.085.15
等抗弯刚度法0.502.110.080.81

Table 2

Parameters of brick element"

材料名称重度γ/(kN·m-3弹性模量E/MPa泊松比υ粘聚力c/kPa内摩擦角φ/(°)渗透系数k/(cm·s-1
粉质粘土19.5150.314518.58×10-5
细砂19.0300.281532.03×10-3
粘土19.5210.354021.02×10-6
卵石21.8800.301045.05×10-3
碎石垫层22.01000.22045.04×10-1
筏板25.030 0000.15---
桩(连续墙)25.0见表10.15---

Table 3

Parameters of geogrid element"

参数
弹性模量E/GPA67
泊松比υ0.33
厚度t/mm5
耦合弹簧单位面积上刚度K/(N·m-32.3×106
耦合弹簧内聚力c/kPa0

Fig.5

Three dimensional model for wide embankment composite foundation in high speed railway station"

Fig.6

Calculated and measured settlement at pile head"

Table 4

Calculated and measured final settlement at end of monitoring period"

方法桩A/mm桩B/mm
桩顶桩间土桩顶桩间土
恒定参数法49.642.257.544.8
等弹性模量法60.548.468.755.4
等桩径法53.343.260.146.7
等抗压刚度法52.045.262.947.3
等抗弯刚度法57.244.263.648.2
三维模型63.849.271.155.7
实测结果60.452.274.661.2

Fig.7

Calculated and measured settlement at soil surface"

Fig.8

Calculated and measured stress distribution at pile A"

Fig.9

Calculated and measured stress distribution at pile B"

Table 5

Calculated and measured final pressure on pile top and soil surface at end of monitoring period"

方法桩A桩B
桩顶应力/kPa桩间土平均压力/kPa桩土应力比桩顶应力/kPa桩间土平均压力/kPa桩土应力比
实测3 126.044.170.9872.288.59.9
三维模型3 282.335.193.5921.193.89.8
恒定参数法2 269.025.788.4656.972.49.1
等弹性模量法3 446.433.3103.4884.290.09.8
等桩径法2 067.824.484.8684.273.99.3
等抗压刚度法2 378.028.284.2732.178.99.3
等抗弯刚度法2 171.229.573.7704.881.18.7

Fig.10

Calculated and measured excess pore water pressure in soil 9 m below end of pile A"

Fig.11

Calculated and measured excess pore water pressure in soil 21 m below end of pile B"

Fig.12

Calculated lateral displacement of pile close to toe of embankment"

Fig.13

Calculated bending moment of pile close to toe of embankment"

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