Application Of FLAC^3D In Stability Pre-judgement Of Excavation Unit Of Archaeology Sites In Moist Environment

Ground and underground water and rainfall are abundant in wet areas. The open test pits of archaeological excavation in such environment are prone to lose stability and even to be destroyed, which pose a serious threat to the safety of the site and the safety of personnel. Based on the study of the application of FLAC^3D in foundation pit, a method of applying this numerical analysis method in archaeology excavations is put forward in this article, which can make a reasonable prediction and analysis of the deformation and stability of the test pits, verify the result of numerical analysis by a real engineering, discusses the feasibility of the FLAC^3D in stability pre-judgement of archaeology excavation unit. The research results show that:（1） According to engineering experience, both straight wall and terraced excavation methods are chose. At the beginning of excavation, the deformation of pit wall is rotation-sliding along the potential slip surfaces, The rotation-sliding angle of pit wall in setback type is larger than the vertical pit wall. Along with the excavation, the deformation of the pit wall gradually convert into “kick foot”.（2） In the conditions of the simulation excavation, the terraced excavation can obviously reduce the horizontal displacement of the pit wall in the most area, But it will not significantly reduce the displacement extremum of the pit wall, and transfer the area of displacement extremum into the deeper place in the pit wall where is closer to the bottom of the pit. Terraced excavation can transferred the danger zone to the bottom of the pit, the bottom of the pit can restrain the horizontal displacement of the pit wall, so terraced excavation can improve the stability.（3） In the conditions of the simulation excavation, the horizontal displacement extermum of pit wall is from 4.2mm to 4.4mm, on the basis of the external conditions, the simulation excavation unit can achieve a stable state.（4） According to the comparative analysis of field monitoring and numerical simulation results, the conclusons can be drawn:① The results of numerical simulation are consistent with the field monitoring data, the displacement and deformation are consistent with the monitoring results, the method of numerical calculation is correct.② By adopting the strength reduction method, we can predict the condition of the unstable failure of the simulation excavation unit which is caused by its own soil mechanical properties reducing. The result of numerical simulation shows that the zone of high shear strain increase is consistent with the sliding zone.In conclusion, FLAC^3D can be applied to analysis deformation and predict the stability of the archaeological excavation unit which is located in the moist environment, With the basic geological data and the size of the archaeological excavation unit, the stability and deformation of the test pits can be predicted by using numerical simulation software, which can provide reference for the excavation support.