湿陷性黄土对深基坑变形的影响及控制技术研究

Influence of Collapsible Loess on Deformation of Deep Foundation Pit and Control Technology Research

由于湿陷性黄土在受水浸湿状态下,强度迅速降低,若仅按干燥状态下的土体物理力学性质进行基坑支护,会导致围护结构强度计算不足,使基坑围护体系及周围土体产生较大变形,严重时会导致周围建筑物坍塌,产生严重的安全隐患。本文以西安地铁1号线某深基坑施工为依托,应用FLAC3D软件建模分析了在干燥状态下与有水浸湿状态下,基坑支护结构和坑周土体的变形规律,研究了湿陷性对基坑围护结构及周围地表的影响,并提出相应的变形控制建议。结果表明:湿陷性黄土基坑围护结构的变形趋势在干燥状态与浸水状态下均表现为“抛物型”,在完全湿陷状态时围护结构变形相对于干燥状态下增加约45%;湿陷性黄土基坑周围地表最大沉降相对于干燥状态下增加约69%。针对湿陷性黄土区域基坑开挖,施工方应尽可能避免雨季施工,提高施工效率,在基坑附近布置降水井,实施相应的防渗措施。

Due to the wet trapping loess in the water-soaked state,its strength decreases rapidly,if only according to the physical and mechanical properties of the soil in the dry state of the pit support,it will lead to insufficient calculation of the strength of the enclosure structure,so that the pit enclosure system and the surrounding soil to produce a large deformation,and in serious cases,it will lead to the collapse of the surrounding buildings,resulting in a serious safety hazard.Bases on the construction of a deep foundation pit of Xi'an Metro Line 1,this paper applies FLAC3D software to model and analyze the deformation law of the foundation pit support structure and the soil body around the pit in the dry state and the water-soaked state,and investigates the effect of wetness on the foundation pit support structure and the surrounding surface,and puts forward the corresponding deformation control suggestions.The results show that the deformation of the enclosure structure of the wetted loess pit is"parabolic"in both dry and submerged states,and the deformation of the enclosure structure increases by about 45%in the fully wetted state compared with that in the dry state;the maximum settlement of the ground surface around the wetted loess pit increases by about 69%in comparison with that in the dry state.For foundation pit excavation in wet subsidence loess area,the builders should avoid the construction in the rainy season as much as possible,improve the construction efficiency,arrange dewatering wells near the foundation pit and implement corresponding anti-seepage measures.