The Geological Disaster Development Characteristics And Stability Evaluation In Southern Margin Continental Slope In Zhujiang River Mouth Basin

In the northern continental slope of South China Sea,there are a lot of geology disasters.The disasters may lead to potential dangers to ocean engineering.The stability evaluation of the marine continental slope is limited,and the quantitative evaluation factors are influenced by human in past.In the stability study of marine continental slope,although seismic factor was considered as an impact factor,the research time and the methods adopted by researchers have some limitations,the northern South China Sea region"50 year beyond the probability of 10%ground motion peak acceleration"was not considered as a parameter in the marine slope stability evaluation system.The existing evaluation methods did not include the measurable factors that are affecting the stability of the slope,nor can they reflect the relationship between the factors.The basic relationship in the evaluation of the marine continental slope stability was still not deduced.At present,there is still no evaluation partition based on the earthquake acceleration value,the topographic slope value,the marine soil physical properties indexes and so on.Therefore,based on a large number of engineering geological data and exploration data measured in marine sediments in Zhujiang river mouth basin,this paper has carried out a thorough research and discussion in the following aspects:?1?Based on the method of Circular Arc Sliding in the theory of limit equilibrium,this paper has deduced the evaluation formula of marine continental slope stability,which includs the physical properties of marine soil,terrain slope,and earthquake acceleration.?2?Based on Cone Penetration Test?CPT?,field Vane Shear Test?VST?and laboratory analysis of the data from three deep water detection points in Baiyun Sag of Zhujiang river mouth basin region,the paper has revealed the relation curves of undrained shear strength and CPT through polynomial fitting.This paper has deduced the fitting curve of penetration coefficient(N_k,N_kt).The N_k,N_ktt values of the three measuring points are 7.48-9.98 and 14.93-19.78,respectively.Because the test data of the soils in deep waters are limited and valuable,the reliability of the relationship needs to be verified further.?3?According to different geomorphic units of the submarine landslides,the Zhujiang river mouth basin in 160-1280m deep have been divided into four large-scale landslide zones.They are from NE to NEE,ranging in size from 4km² to 800km²,in19°-20°N,114°-118°E.This paper has put forward the main influencing factors of landslide activities including seismic activity,current and sediment rapid accumlation.?4?Based on the differences of rock,soil and geological structure characteristics of the Zhujiang river mouth basin,the paper has formed three small zonings in the nothern South China Sea,which are the coastal area of Guangdong,the coastal area of Fujian,Zhujiang river mouth basin and shallow water area in Taiwan.Finally this paper has comparatively studied seismic parameter values of b.The b values are0.9498,0.6452 and 0.4865 in the coastal area of Guangdong,the coastal area of Fujian,Zhujiang river mouth basin and shallow water area in Taiwan respectively.?5?According to the evaluation formula of marine continental slope stability and the undrained shear strength values of three deep water soils at different depths in the Zhujiang river mouth basin,the critical seismic acceleration for sliding on the seabed slope has been derived.The value of k_c/a_maxax can show the stability distribution in the study area.According to the 5-grade stablity classification in Zhujiang river mouth basin,through an overall evaluation,this paper has worked out the stability distribution map of the southern continental slope in the Zhujiang river mouth basin.