基坑斜–直交替支护桩工作机理分析
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摘要
在基坑工程中,可将部分竖直悬臂支护桩倾斜一定角度后形成倾斜桩,利用冠梁连接交替布置的竖直悬臂桩与倾斜桩可形成基坑斜–直交替支护体系。已有工程实测表明,基坑斜–直交替支护桩具备良好的抗倾覆和变形控制能力;然而,目前尚缺乏对其工作机理的认识。提出了基坑斜–直交替支护桩的3个工作机理效应,即:刚架效应、斜撑效应和重力效应。以支护结构变形和坑外土体沉降为评价标准,对3项效应进行分析。结果表明:①由于冠梁的连接作用,斜桩与直桩形成一个整体刚架体系,可有效减小桩身和土体变形;②斜桩侧壁摩擦是斜桩对直桩支撑力发挥的关键因素,若斜桩侧壁光滑,基坑斜–直交替支护桩的支护能力与悬臂直桩几乎相同;③斜直桩桩间土与支护体系形成一个整体,可一定程度提高支护体系抵抗基坑变形的能力。
In excavation engineering, an inclined-vertical retaining pile system can be formed by connecting the cantilever piles and the inclined piles. The previous case histories indicate that the inclined-vertical retaining piles have the advantage in overturning resistance and deformation control. However, the insight into the working mechanism of inclined-vertical retaining piles is limited. Three mechanisms are proposed in this investigation, that is, frame effect, supporting effect, and gravity effect.Taking the deformation of retaining structures and the ground settlement as the criteria, the contribution of these work mechanisms is analyzed. The results indicate that(1) The formed frame system can significantly decrease the structural deformation and ground settlement.(2) the side friction in inclined piles is vital to the supporting effect on the cantilever piles.(3) the soil between the inclined and vertical piles has a limited effect on the structural deformation.
In excavation engineering, an inclined-vertical retaining pile system can be formed by connecting the cantilever piles and the inclined piles. The previous case histories indicate that the inclined-vertical retaining piles have the advantage in overturning resistance and deformation control. However, the insight into the working mechanism of inclined-vertical retaining piles is limited. Three mechanisms are proposed in this investigation, that is, frame effect, supporting effect, and gravity effect.Taking the deformation of retaining structures and the ground settlement as the criteria, the contribution of these work mechanisms is analyzed. The results indicate that(1) The formed frame system can significantly decrease the structural deformation and ground settlement.(2) the side friction in inclined piles is vital to the supporting effect on the cantilever piles.(3) the soil between the inclined and vertical piles has a limited effect on the structural deformation.
引文
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[2]MAEDA T,SHIMADA Y,TAKAHASHI S,et al.Design and construction of inclined-braceless excavation support applicable to deep excavation[C]//International Conference on Soil Mechanics and Geotechnical Engineering.Paris,2013:2051-2054.
[3]SEO M S,IM J C,KIM C,et al.A study on the applicability of retaining wall using batter piles in clay[J].Canadian Geotechnical Journal,2016,53:1195-1212.
[4]郑刚,白若虚.倾斜单排桩在水平荷载作用下的性状研究[J].岩土工程学报,2010,32(增刊1):39-45.(ZHENGGang,BAI Ruo-xu.Behaviors study of inclined single row contiguous retaining piles under horizontal force[J].Chinese Journal of Geotechnical Engineering,2010,32(S1):39-45.(in Chinese))
[5]PLAXIS B V.PLAXIS 3D tutorial manual[M].Anniversary ed.Delft:Plaxis Bv,2010.
[6]HSIEH P G,OU C Y,SHIH C.A simplified plane strain analysis of lateral wall deflection for excavations with cross walls[J].Revue Canadienne De Géotechnique,2012,49(10):1134-1146.
[7]GOH A T C,ZHANG F,ZHANG W,et al.A simple estimation model for 3D braced excavation wall deflection[J].Comput Geotech,2017,83:106-113.
[8]JARDINE R J,POTTS D M,FOURIE A B,et al.Studies of the influence of non-linear stress-strain characteristics in soil-structure interaction[J].Géotechnique,1986,36(3):377-396.
[9]OU C Y,HSIEH P G,CHIOU D C.Characteristics of ground surface settlement during excavation[J].Canadian Geotechnical Journal,1993,30(5):758-767.
[10]CHEN R,MENG F,LI Z,et al.Investigation of response of metro tunnels due to adjacent large excavation and protective measures in soft soils[J].Tunn Undergr Space Technol,2016,58:224-235.
[11]CLOUGH G W,O’ROURKE T D.Construction induced movements of in situ walls[C]//Proceedings of the Design and Performance of Earth Retaining Structures,ASCE.New York,1990:439-470.
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