Journal of Shandong University(Engineering Science) ›› 2019, Vol. 49 ›› Issue (3): 63-72, 79.doi: 10.6040/j.issn.1672-3961.0.2018.345

• Civil Engineering • Previous Articles     Next Articles

Influence rule of foundation pit supporting structure and its adjacent composite foundation distance

Lianxiang LIab(),Lu BAIab,Tianyu CHENab,Xiangkai JIab   

  1. a. School of Civil and Hydraulic Engineering, Shandong University, Jinan 250061, Shandong, China
    b. Foundation Pit and Deep Foundation Engineering Technology Research Center, Shandong University, Jinan 250061, Shandong, China
  • Received:2018-08-11 Online:2019-06-20 Published:2019-06-27
  • Supported by:
    济南市科技计划项目(201201145)

Abstract:

Based on the centrifugal test of the close relationship between the composite foundation and the supporting structure, the PLAXIS software was used to establish a numerical model of the foundation pit with a certain distance between the composite foundation and the supporting structure. This model was used to study the influence of the width of the strip on internal force and displacement of the composite foundation and retaining structure. The results showed that the distance law could be divided into three sections: when the width of the soil strip increased from 0 to 6 m, the axial force of the CFG pile and the pile-soil stress ratio increased, and the obstruction effect was obvious. It was advisable to establish a lateral pressure calculation method that considered the lateral stiffness and the obstruction effect to actively control the displacement. When the width of the soil strip was 6 m to 18 m, the axial force of the CFG pile and the pile-soil stress ratio were steadily reduced. When the width of the soil strip was increased to 18 m or more, there was no longer any influence between the new foundation pit and the existing composite foundation. The research results clarified the design direction of foundation pits under different widths of soil and the safety protection focus of similar foundation pit engineering, which laid a foundation for further establishing the design theory of such foundation pits.

Key words: composite foundation, support structure, strip width

CLC Number: 

  • TU43

Fig.1

Foundation pit of near building"

Fig.2

Geometric expansion numerical model"

Table 1

parameters of CFG model piles and prototype"

桩参数置换率尺寸/mm×mm(×mm)桩间距/mm
模型0.031 320×0.5×350100
原型0.031 3400×14 0002 000
数值模型0.031 3800×14 0003 200

Fig.3

Centrifugal test monitoring pile distribution"

Table 2

Calculation parameters of soil HSS model"

项目Dr干密度γd
(/kN·m-3)
粘聚力
c/kPa
平均粒径
d50/mm
项目天然孔隙比eeminemax内摩擦角
φ
福建砂85%15.900.17取值0.6630.6 1170.95733

Table 3

Component calculation parameters"

部件密度/(kg·m-3)弹性模量/MPa泊松比
支护板2.768.9×1030.33
CFG桩2.768.9×1030.33
褥垫层2.5450.33

Fig.4

Displacement of support structure"

Fig.5

Moment of support structure"

Fig.6

Earth pressure at an excavation depth of 10 m"

Fig.7

Axial force monitoring pile's axial force results"

Fig.8

Surface subsidence"

Fig.9

Moment monitoring pile's bending moment results"

Fig.10

Schematic diagram of the relationship betweencomposite foundation and foundation pit"

Fig.11

Pile 1 axial force and soil strip width relationship"

Fig.12

Peak axial force of piles"

Fig.13

Schematic diagram of soil compressive stress"

Fig.14

Relationship between pile-soil stress ratioand soil strip width"

Fig.15

Relationship of pile displacement and soil strip width"

Fig.16

The relationship between pile displacementand position"

Table 4

Comparison of numerical model settings"

编号组别土条宽度/m上覆荷载/kPaCFG桩
1有桩有载0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24180
2无桩有载0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24180
3无桩无载

Fig.17

Comparison of three groups of model diagrams"

Fig.18

Supporting structure bending moment underdifferent soil strip width"

Fig.19

Displacement of supporting structures underdifferent soil strip widths"

Fig.20

Support structure displacement reduction"

Fig.21

Different side strip width under the supportingstructure side pressure"

Fig.22

Earth pressure redundancy"

Fig.23

Surface subsidence"

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