分层降水开挖对坑内土体变形影响的实测与试验分析
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摘要
在超深基坑施工中,总会涉及分层降水与开挖的过程,坑内土体经历了反复加卸荷的作用,会改变土体的有效应力,产生变形等,从而土体的各种力学性状与单纯的考虑开挖卸荷或降水加荷不同。针对天津站交通枢纽工程这样软土地区的大型超深基坑工程,结合现场监测资料分析和室内三轴试验模拟,围绕超深基坑降水开挖对坑内土体变形特征的影响而展开研究。通过三轴试验揭示了降水对于坑内土体变形性状的影响规律,并结合实测数据分析了基坑变形(包括坑内立柱沉降、地下连续墙位移)随着相应的施工工况的进度而变化的趋势,尤其是基坑分层降水开挖对基坑坑内变形特征的影响效果。
Dewatering and excavation are concerned during the construction of deep foundation pits,this process may cause change in the effective stress and the deformation of the soil in the foundation pits.Therefore the mechanical properties of soil will be changed considering the combined effect of dewatering and excavation.Based on the Tianjin Transport Hub project,a large super-deep excavation work in soft soil,the analysis of field monitoring data and the triaxial test simulation,the effect of foundation excavation of super-deep pit on the deformation of soil behavior was carried out.It revealed the influence of dewatering for the deformation of soil inside the foundation pit through triaxial tests,and combined with the analysis of monitoring data the pit deformation,including the pile settlement inside the pit,the settlement of the walls and the surrounding buildings,was analyzed considering the construction steps.The the focus of the study was the effect of soil deformation induced by the layered process of dewatering and excavation of the super-deep foundation pit.
Dewatering and excavation are concerned during the construction of deep foundation pits,this process may cause change in the effective stress and the deformation of the soil in the foundation pits.Therefore the mechanical properties of soil will be changed considering the combined effect of dewatering and excavation.Based on the Tianjin Transport Hub project,a large super-deep excavation work in soft soil,the analysis of field monitoring data and the triaxial test simulation,the effect of foundation excavation of super-deep pit on the deformation of soil behavior was carried out.It revealed the influence of dewatering for the deformation of soil inside the foundation pit through triaxial tests,and combined with the analysis of monitoring data the pit deformation,including the pile settlement inside the pit,the settlement of the walls and the surrounding buildings,was analyzed considering the construction steps.The the focus of the study was the effect of soil deformation induced by the layered process of dewatering and excavation of the super-deep foundation pit.
引文
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[2]张永波,孙新忠.基坑降水工程[M].北京:地震出版社, 2000.(ZHANG Yong-bo,SUN Xin-zhong.Foundation pit dewatering engineering[M].Beijing:Seismic Publishing ??House,2000.(in Chinese))
[3]金小荣,俞建林,祝哨晨,等.基坑降水引起周围土体沉降性状分析[J].岩土力学,2005,26(10):1575-1581.(JIN Xiao-rong,YU Jian-lin,ZHU Shao-chen,et al.Analysis of behaviors of settlement of pit's surrounding soils by dewateringtJ].Rock and Soil Mechanics,2005,26(10):1575 - 1581.(in Chinese))
[4]刘国彬,刘金元,徐全庆.基坑开挖引起的土体力学特性变化的试验研究[J].岩石力学与工程学报,2000,19(1): 112-116.(LIU Guo-bin,LIU Jin-yuan,XU Quan-qing. Testing study on variation of mechanical characteristics of soil due to excavation[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(1):112 - 116.(in Chinese))
[5]潘林有,胡中雄.深基坑卸菏回弹问题的研究[J].岩土工程学报,2002,24(1):101-104.(PAN Lin-you,HU Zhong-xiong.Experimental study on the resilience of pit under unloading[J].Chinese Journal of Geotechnical Engineering,2002,24(1):101 - 104.(in Chinese))
[6]陈永福,曹名葆.上海地区软黏土的卸荷——再加荷变形特性[J].岩土工程学报,1990,12(2):9-18.(CHEN Yong-fu,CAO Ming-bao.The deformation characteristics of soft clay under unloading and reloading in Shanghai[J]. Chinese Journal of Geotechnical Engineering,1990,12(2):9 - 18.(in Chinese))
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