Study On The Stability Of Loess High Slopes In Baojixia Water Division Project

As the"First Granary"in Shaanxi,Baojixia irrigation district is one of the ten biggest irrigation districts of nation,and is also the biggest irrigation district of the Guanzhong plain.It has been playing an very important role in economy and the social development of Shaanxi.However,the two sides of the Baojixia's main ditch which is 98km are high loess slopes , the stability of the slopes is critial in this area.If the treatment of the slopes isn't good,not only bringing the normal run of the Baojixia in trouble,but also meeting great damage on man power and economy.Thus,studying the stability of the slopes occupies an important position in the project.It not only can provide measures to treat the Baojixia high loess slopes ,but also can provide references to the same kind of engineering for its typical.To study the stability of the slopes, firstly, various methods of the slope stability analysis at home and abroad are summaried and studied systematically in this paper ,then many datums about the slopes of Baojixia are collected and analyzed, and investions are also taken.Through the investigation,the failure forms,the existent problems of the high slopes and the measures which are taken to protect the slopes are found out.Secondly, based on the datums collected, using grey correlation grade method and the method of orthogonal test, the main influence factors of the high loess slope stability in Baojixia water division project are analyzed;Thirdly,the slopes at Nanshetou and Weijiabao are studied.The slope stability are checked,the styles of the slopes are designed and the stability of the designed slope styles is checked in different conditions.Finally,the influence of the rainfall infiltration to the slope stability are discussed.According to the research,this paper obtaine some results as follows:First of all,on the basis of investigation,analysis and research,the destruction forms and the stability influence factors of the Baojixia loess high slopes are found out.Then the destruction forms are analysised qualitatively,and the effective measures defending and harnessing the slopes are brought forward.Secondly, using grey correlation grade method to analyze the main influence factors of the high loess slope stability in Baojixia water division project , the results indicate that the angle of internal friction and cohesion are the principal factors influencing the slope stability ,and by the method of orthogonal test , the results indicate that the influence of earthquake is also significant on the slope stability. Thirdly,according to summarize the experiences designing slopes that a large amount of work that forefathers have done, and on the basis of daums about Baojixia loess slopes and investigation,the stability of the slopes at Nanshetou and Weijiabao have been checked in different conditions.The results show that the slopes at Nanshentou is in the marginal steday state or non-steady state when the water content is higher than 25%. And the stbility of the slopes at Weijiabao is accord with the fact in 1984. Then proper slope styles are designed and the stability is checked in different conditions.Finally,according to analysis the rainfall datums,the consanguineous relationsheeps between the stability of the slopes and the rainfull is found out.Then both the relationsheep between the factor of safety and different rainfall infiltration depth ,and between the different water content and the factor of safety,are all discussed.On the basis of the analysis ,the dangerest infiltration depth for a certain slope is brought forward,and the influence of the rainfull to the slope stability is analysised qualitatively.Therefore, through forecasting the rainfall,the stability of a certain slope can estimate by compare the dangerest inflitration depth when the rainfull datums is enough.In addition,when designing the slope style or checking the stability,proper checking conditions can be choosed considering the rainfull datums.