Comprehensive Analysis And Numerical Simulation For Qulong Landslide Dam Event In The Late Pleistocene

The Qulong landslide dam event is located in the Benzilan-Batang zone of the upper Jinsha River.Affected by uplift of the Tibetan Plateau,tectonic activity in the study area is very strong and the geological environment in here is very complex,which cause a mass of landslide dams in early geological time.The upper reaches of the Jinsha River are one of the largest rivers in the southwest of region of China,which have the largest potential of water resources.In order to guarantee the safety of the development and utilization of water resources in the upper reaches of the Jinsha River,it is necessary to understand the geological environment in early geological time through the study of the early landslide dam events in the zone.In this study,the Qulong landslide dam event in the upper Jinsha River is analyzed in detail.First,through the scale investigation of barrier lake and the residual distribution investigation of landslide dam,the large scale of Qulong landslide dam event is clearly understood during the investigation.Then,through the topography and materials grading analysis in the source area and lacustrine sediment fating analysis in the barrier lake,combined with the historical background of the uplift of the Tibetan Plateau,the characteristics of early glacier landform and current glacier landform,the information of geological environment of Qulong landslide dam event is obtained.History data show that more than 90%of barrier lakes are formed because of the high speed landslides caused by earthquakes.The landslide in Qulong source area was identified based on the information of the topography in here.The forming process of Qulong landslide dam was analyzed and the parameters of seismic causing the Qulong Landslide are calculated.Finally,in order to analyze the movement characteristics of high speed landslide in Qulong,a well-balanced numerical model is established and the SFLOW software is developed to solve the numerical model.Based on the above work,the study expounds the historical evolution process of Qulong landslide dam event.The achievement of the study are as follows:1.Through the investigation of Qulong landslide dam event,it can be seen that the scale of the landslide dam event is very large.The volume of landslide dam body is estimated more than 2×10~8 m~3 and the thickness of lake sediment reaches about 100 m.2.Through the current and the early glacial geomorphic features and the particle size distribution characteristic of early glacial moraine material,the source area of Qulong basin was identified to be the early glacial landform,and the source materials is considered to be glacial moraine.3.Through collecting a large number of data about the formation mechanism of large landslide dams,it is found that the barrier lakes caused by large landslide dam events are usually formed because of the high speed landslides caused by earthquakes.Combined with the accumulation and movement characteristics of the glacier moraine in current glacial landform,Qulong landslide is identified based on the topography in source area,and its landslide movement mechanism is analyzed.4.Through optically stimulated luminescence dating analysis of lacustrine sediment in the barrier lake,combined with the historical background of the uplift of the Tibetan Plateau and the information of climate change in Quaternary,it can be seen that Qulong landslide dam event occurred the transition period from Penultimate Glaciation to the Last Interglaciation.In the transition period,the uplift of the Tibetan Plateau is very strong and the climate change is very sensitive.5.According to the occurrence period of Qulong landslide dam event,it can be inferred that materials of Qulong landslide is glacial moraine formed during Penultimate Glaciation period.Its physical and mechanical parameters of the material is given with field large-scale direct shear test and physical test of moraine in southeast Tibet.6.According to the landslide seismic analysis method proposed by Jibson(2015),combined with the regional earthquake point distribution,the parameters of seismic causing the Qulong landslide are calculated.it is concluded that when the epicenter is located in the Diqing area,the earthquake magnitude inducing Qulong landslide is around 8.0,and when the epicenter located in their area,the earthquake magnitude inducing Qulong landslide is around9.0.7.Through the numerical simulation analysis of high-speed clastic flow caused by the high speed Qulong landslide,it can be seen that the speed of clastic flow reaches 41 m/s or so,and the clastic flow blocks the early Jinsha River channel which its thickness reaches 100 m or so,the largest up to 111 m and its length is more than 4.5 km.Moreover,the high-speed clastic flow runs over the front of Yinduba platform.8.Through detailed analysis of Qulong landslide dam event and numerical simulation calculation of the movement characteristics of the high-speed clastic flow caused by the high-speed Qulong landslide,the study expounds the historical evolution process of Qulong landslide dam event and demonstrates the rationality of hugely thick lacustrine sediment formation and the spatial distribution of the residual materials of Qulong landslide dam.Furthermore,in order to study the movement characteristics of the high-speed clastic flow caused by the high-speed Qulong landslide,this study establishes a well-balanced numerical model and develops SFLOW software to solve the numerical simulation model.the model and software have the following characteristics and innovations:1.The model uses the complex terrain digital processing technique,which can effectively and quickly realize digital extraction,processing and storage of Terrain data in complex research areas.2.The model adopts the slope limited linear reconstruction technique,which can guarantee the well-balanced numerical format,avoids the problem of numerical oscillation,and improves the precision of the numerical space.3.The model considers the problem of dry/wet boundary treatment,guarantee water conservation,and avoids negative water depth problem in simulation calculation.Moreover,based on above boundary treatment work,this model gives a kind of dry-wet tracking technique,which speeds up the calculation in numerical simulation.4.The model gives fully implicit format process to deal with the bed friction source term in numerical simulation,which can avoid the defect of general display and semi-implicit format.Moreover,based on the physical properties of the friction,the model gives a reasonable limit of the bottom friction value and direction,which further ensure the rationality of the results of numerical calculation.5.SFLOW software uses C++language programming and installs the Qt application development framework tool,which provide the humanized user interface.The software contains the menu module(including the data load,output and etc),the monitoring module of calculation data,simulation calculation progress module and display module of calculation.Through the shallow water flow physical test under complicated topography and two simulation results contrast analysis of actual case,the shallow water flow numerical simulation software simulation calculation results are reasonable and the software program code is valid.