黄土高填方场地裂缝的发育特征及分布规律

Development and distribution characteristics of ground fissures in high loess filled ground

裂缝是高填方场地常见隐患,对工程场地安全和稳定造成影响。基于陕北某黄土高填方场地的裂缝监测和探测资料,分析裂缝的发育特征、分布规律和时间变化,从场地地形条件、填土厚度、变形特征等方面,对裂缝的成因机制进行探讨。研究结果表明,裂缝主要在填方区发育,分布于填方厚度小于15 m及距离挖填分界线20 m以内的区域内,以挖填交界过渡带(挖填厚度≤5 m)为主,裂缝走向与挖填界线或原地基的等高线近似一致;裂缝宽度增大速率逐渐降低,从出现到趋于稳定约需3个月时间;裂缝受降水侵蚀、潜蚀等作用,常伴生发育落水洞,并沿填土与谷坡接茬面延伸发展,距地面最大垂直深度可达7.5 m;沟谷地形、填土厚度差异等引起的差异沉降和水平位移是导致黄土高填方发生裂缝的主要原因。

Fissures are common in high filled ground,it is a potential risk for the safety and stability of engineering sites.Based on the monitoring and detection data of ground fissures in a high loess filled ground in Northern Shaanxi,the development characteristics,distribution regularity and time variation of ground fissures are analyzed,and the formation mechanism of fissures is also discussed according to terrain conditions,thickness of filling and deformation characteristics.The results show that the fissures are mainly developed in the filling ground,and they are distributed in the areas with the thickness less than 15 m and 20 m away from the excavation-filling boundary,the main area is the transition zone between excavation and fill(thickness of excavation and filling is less than or equal to 5 m).The trend of fissures is approximately consistent with the excavation-filling boundary or the contour line of original foundation,the increasing rate of the fissure width decreases gradually,and it takes about 3 months from its appearance to stabilization.The fissures often develop with a sinkhole and extends along the joint surface between the filling and valley slope due to the effect of precipitation erosion and subsurface erosion,with a vertical depth of 7.5 m.The differential settlement and horizontal displacement caused by the difference of gully topography and thickness of filling are the main causes of fissures in high loess filled ground.