中文摘要：

为探明庆阳董志塬地区大厚度自重湿陷性黄土场地的各项湿陷性评价指标,推动场地湿陷性评价体系的发展,在这一地区的代表性场地开展了原位大型浸水试验。采用直径20 m的圆形试坑,利用辐射状布置的机械式沉降观测标对浸水过程中地表和地下各深度土层的沉降进行了观测,利用全站仪对浸水试验前后整个场地的地面变形进行了测量。试验共历时177d,其中试坑注水过程93d,共注水44 119 m^3,浸水引起了试坑内外黄土不同程度的自重湿陷。基于监测数据分析并解释了距试坑中心不同距离处地表湿陷量的发展规律与差异,通过地面沉降等值线得出浸水影响半径为31 m,通过计算各土层原位实测自重湿陷系数获得该场地自重湿陷下限深度为13 m,远小于通过室内试验获得的17 m下限深度,用面积权重法计算得该场地的修正系数β0为1.02,小于规范推荐值1.2。给出了详细的试验设计方案,并在分析讨论的基础上提出了数据处理方式和结果呈现方法,对指导该地区未来的黄土地基勘察设计具有直接的应用价值。

英文摘要：

In order to explore the characteristics of collapsibility of a self-weight collapsible loess site located in the Dongzhiyuan area,and to make the progress of the in-situ loess collapsibility evaluation system,a large scale in-situ immersion test was conducted on a representative site in this area. The diameter of test pool is 20 m,and the settlement of the ground surface and loess layers of different depths were monitored by measuring the solar-arranged mechanical monitor points. In addition,the whole ground surface deformation of the test site was measured with a total station instrument. The test lasted 177 days,and the immersion process,93 days.The water cost was 44 119 m^3,which induced the loess self-weight collapse. Based on the data processing and analysis,the developing regularity of settlement and the differential subsidence between various distances from the middle of the test pool was explained. According to the subsidence contours the influence radius was 31 m. Through calculating the in-situ coefficient of collapsibility, the lower limit depth of the self-weight collapsible loess is 13 m,which is much lower than the result（ 17 m） from a laboratory test. Finally,the value area correction factor β_0was calculated by the area weight method,and the result is 1. 02,which is lower than the number given by the code. In this article,the detail test design was indicated,and the method of data processing and approach of results presented were also presented based on the discussion and analysis.The results have practical value for investigation and design of future engineering construction in this area.Furthermore,the discussions of the in-situ test method and data processing approach are of scientific significance.