| This paper investigated the cutting slope near the south-north passageway of Baohua Mountain in Jurong District,Zhenjiang,Jiangsu Province,China.The deterioration characteristics of different joints in this district and the influence on the slope stability due to the joint deterioration were also studied.Based on the field investigation,although the slope was treated by cutting method in 2013,due to the influence of the fragmentized rock mass,well-developed joints,unloading effect and heavy rainfall,rocks and joints weathered quickly,of which the mechanical property deteriorated seriously.Moreover,the mechanical strength decreased greatly.As a result,massive geological hazards happened,including falling rocks,collapse and sliding.So in this paper,the relations between the joint strength characteristics of different weathering degrees with joint roughness coefficient(JRC)and compression strength(JCS)are mainly studied,respectively.The results of this paper could provide a scientific basis for the treatment of cutting slopes.(1)In the study,a research on the potential landslides was firstly conducted based on the geological background of Zhenjiang city.The geological data of over 300 slopes in the whole city were collected.By importing the coordinates of slope locations into Google Earth,the slopes were classified into soil slopes,rock slopes and rock-soil slopes.Then,statistics of the slopes were carried out according to the current slope conditions of being stable or unstable and the failure modes of these slopes(including collapse,sliding,rockfall,and et al.).At last,the causes for the geological hazards such as rockfall,collapse and sliding were analyzed and summarized based on the landforms,climate,geological structure characteristics,engineering geological conditions and human activities of Zhenjiang city.(2)In this paper,joints in the moderate weathered layered-cataclastic sandstone and weakly weathered layered limestone in the slope are chosen to be studied.Because of the difficulty of field sampling,JRC-JCS model proposed by Barton,combined with M-C model is applied to analyze the data which have been measured in the field.The range of JRC of the joints is between 0 and 4,provided by the filed experience.The results of statistics show that the shear strength(τ),internal friction angle(φ)and cohesion(c)of joints in both sandstone and limestone all increase linearly as JRC increases.If JRC remains the same,as d(defined by the distance between the study point and the slope plane along the joint)increases,JCS of the joints will increase gradually,while the three parameters(τ,φ and c)will increase logarithmically with the increasing of JCS.(3)According to the statistics,the functions of d with τ,φ and c of the joints in the layered-cataclastic sandstone and the layered limestone are fitted,respectively;the functions of the three parameters and the corresponding deterioration degrees with d are worked out,respectively.The results show that,with the same value of d,the strength parameters(τ,φ and c)of the joints in the sandstone are smaller than those in the limestone.In the sandstone,as d reduces,the deterioration degree of the joints is greater than that of the joints in the limestone.Generally speaking,the sandstone will be more easily weathered than the limestone,and the strength of joints varies with different kinds of structural types of rock mass.The strength of joints in layered rock mass is larger than that in layered-cataclastic rock mass,which means the structural integrity and weathering degree of the rock mass have a direct influence on the strength index.The strength will be smaller as the weathering degree is greater,which will influence the stability of the slope.At last,the joints of cataclastic shale are studied,and the variation of JCS before and after rainfall was released that a great degree of deterioration comes into being after rainfall.(4)According to the geological analysis,the failure mode of the slope is confirmed and an evaluation of the slope stability is conducted based on the mode.The analysis focuses on plane sliding.The slopes are assumed at a critical steady state in both sandstone area and limestone area.Then the critical height(Hcr)of the sliding body when the plane sliding is about to emerge is calculated.Results show that the Hcr of the joint in sandstone is smaller than that in limestone,indicating that when rocks deteriorate gradually and the strength properties are getting worse,the slope in sandstone area will slide before that in limestone area does. |
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