Study On The Stability For Loess Trench Of Diaphragm Wall Foundation

In this paper, the rectangular diaphragm wall foundation excavation of a great-span bridge, which was located on 209 national highway in loess plateau, in Shanxi province, was studied. The characteristics of loess was systemic dissertated and the site construction surveyed, the engineering geologic condition of testing field was illustrated, and the local unstable failure model was proposed, so the stability investigation of trench excavation of diaphragm wall was carried though in loess strata.Based on the analysis of trench stability literature and data in both here and abroad, the universal stability analysis method of trench excavation was proposed by systemic summed-up the status of investigation and development of trench stability. The physical and mechanical properties of loess were analysed and summarized, the engineering properties of loess, in particular for the joint properties were systemic expatiated in loess.On the basis of the engineering geologic condition of testing field, the feature of construction site trench collapse was analyzed in detail, a reasonable trench excavation failure model of rectangular diaphragm wall was established, and the failure models of trench excavation were discussed and investigated farther in loess strata.Based on the charateristics of loess and the construction of the trench, there are 10 different numerical modes. The numerical simulation analysis method (Flac) was employed to analyse the trench excavation stability of rectangular diaphragm wall in loess strata, the results of the limit excavation depth value of trench stability, and its failure characteristics and varying law in were obtained in loess strata.Investigation indicated that the key factors influencing on the trench wall stability were as such property of loess, shape of diaphragm trench, excavation depth, and construction.