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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2014, Vol. 8 Issue (2) : 124-139     https://doi.org/10.1007/s11709-014-0255-9
RESEARCH ARTICLE |
Field testing of geosynthetic-reinforced and column-supported earth platforms constructed on soft soil
Qiangong CHENG(),Jiujiang WU,Dongxue ZHANG,Fengping MA
Department of Geological Engineering, Southwest Jiaotong University, Chengdu 610031, China
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Abstract

This paper is focused on the behavior of geosynthetic-reinforced and column-supported (GRCS) earth platforms in soft soil. By analyzing the data of a 15-month long field monitoring project, the bearing behavior and effectiveness of GRCS earth platforms are discussed in detail. It can be found that the soil arching is generated when the filling reaches a certain height. The measured pressure acting on the soil in the center of four piles was smaller than that acting on the soil between two piles. The elongation and the tension of the geogrid located in the soil between piles are both larger than the corresponding values on the pile top. The skin friction of piles is relatively small in the soil layer with low strength and the load transfer of the axial force in those layers is significant; meanwhile, the opposite situation occurs in the soil layer with high strength. The pore water pressure at shallow locations increases slightly with the filling height and is greatly affected by the increasing filling load. The layered settlement is directly proportional to the filling height, and the corresponding amount is relevant to the locations and the properties of specific soil layers. Additionally, the lateral displacement of the embankment increases with greater loading and decreases with increased depth. These suggest that the use of GRCS system can reduce lateral displacements and enhance the stability of an embankment significantly.

Keywords geosynthetic-reinforced and column-supported (GRCS) earth platforms      soft soil      bearing behavior      settlement and deformation      field testing     
Issue Date: 19 May 2014
 Cite this article:   
Qiangong CHENG,Jiujiang WU,Dongxue ZHANG, et al. Field testing of geosynthetic-reinforced and column-supported earth platforms constructed on soft soil[J]. Front. Struct. Civ. Eng., 2014, 8(2): 124-139.
 URL:  
http://journal.hep.com.cn/fsce/EN/10.1007/s11709-014-0255-9
http://journal.hep.com.cn/fsce/EN/Y2014/V8/I2/124
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Qiangong CHENG
Jiujiang WU
Dongxue ZHANG
Fengping MA
Fig.1  Soil description, soil profile and CPT data
soil typesdry density/(g·cm-3)wet density /(g·cm-3)water content /%porosity/%
silt and cohesive soil1.842.0813.829.5
sand and organic soil1.862.0712.628
round gravel and dust1.842.1413.229.3
rubble soil1.862.0912.728.5
Tab.1  The measured values of subgrade fillings
Fig.2  Cross-sectional view of the strengthening scheme (unit: m).
Fig.3  Layout of the earth pressure cells
Fig.4  Placement of the main instruments. (a) Fastened displacement transducers on the geogrid; (b) settlement tube tied up with magnetic cores; (c) monitored inclinometer tubes; (d) Installed pore pressure gauges
categoryearth pressure cellspore pressure gaugeswire stress gaugesmagnetic coresdisplacement transducersinclinometer tubes
amount17132615454
embedded time08/29/0908/21/09 ? 08/30/0906/20/0908/21/09 ? 08/30/0909/21/0908/21/09 ? 08/30/09
measuring range0.4 MPa0.4 MPatension range: 20 kNpressure range: 10 kNaccuracy: 1 mmMaximum: 50 m30 mmaccuracy: 0.1 mmmaximum: 40 m
working principlevibrating stringvibrating stringvibrating stringmagnetic typevibrating stringresistive
locations7 on pile caps, 10 in soil between piles1 hole, 1 gauge13 in each testing piles22 in each settlement tube2 on pile cap, 3 in soil between piles2 in each side slope of the embankment
Tab.2  Types and quantities of instruments in the testing section
Fig.5  Layout of the substructure instruments (unit: m). (a) Layout of the pore pressure gauges and the wire stress gauges; (b) layout of the settlement tubes and the inclinometer tubes.
Fig.6  Curves of earth pressure versus filling height and time.
Fig.7  Earth pressure on the pile top and soil pressure between piles plotted with filling height and time.
Fig.8  Curves for the pile-soil stress ratio plotted with filling height and time
instrument IDoriginal lengthl0/mmelongationS/mmtensile strengtht/(kN/m-1)elongation rater/%tensionT/N
FDT2221.111000.5111
FDT3223.51001.6350
Tab.3  Calculation results for the geogrid
Fig.9  Elongation measured by the flexible displacement transducer with the filling height as a function of time
Fig.10  Curves for the axial force measured by TP1 as a function of depth
Fig.11  Distribution of the axial force measured by TP2 as a function of depth
Fig.12  Side friction measured by TP1 as a function of depth
Fig.13  Side friction measured by TP2 as a function of depth
Fig.14  Curves for the pore water pressure at shallow locations with increasing filling height
Fig.15  Curves for the pore water pressure at deep locations with increasing filling height
Fig.16  Curves for the layered settlement measured by ST1 and the filling height as a function of time
Fig.17  Curves for the layered settlement measured by ST2 and the filling height as a function of time
Fig.18  Curves for the layered settlement measured by ST3and the filling height as a function of time
Fig.19  Curves for the layered settlement measured by ST4 and the filling height as a function of time
Fig.20  Curves for the layered settlement measured by ST5 and the filling height as a function of time
Fig.21  Curves for the layered settlement measured by ST6 and the filling height as a function of time
Fig.22  Contours of the foundation settlement on the 45th day (unit: mm)
Fig.23  Contours of the foundation settlement on the 113th day (unit: mm)
Fig.24  Contours of the foundation settlement on the 142nd day (unit: mm)
Fig.25  Curves for the lateral displacement measured by IT3 with time
Fig.26  Curves for the lateral displacement measured by IT4 with time
Fig.27  Curves for the maximum lateral displacement as a function of time and load
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