| Debris flow is a very common kind of mountain disaster,which refers to the geological movement phenomenon of starting,moving and accumulating of loose accumulation material in hillsides or valleys under the action of hydrodynamic force caused by rainfall,melting water of ice and snow,glacier lake burst floods,barrier dam failure,under favorable terrain conditions.With the development of the Western Development Strategy in Tibet,the linear engineering projects such as roads and railways have been promoted to high altitude areas.In the process of line selection,design,construction and operation of linear engineering,there will inevitably face debris flow disaster caused by ice lake break.Dongcuoqu gully is located in Lajiu Township,Luolong County,Tibet.The downstream of the gully mouth is the residential area and the station and bridge of the proposed linear project.Once a large-scale debris flow breaks out,it will seriously threaten the construction,operation of the project and the safety of local people's life and property.Therefore,this paper firstly analyzes the development characteristics of the Dongcuoqu gully through field investigation and indoor remote sensing interpretation,and then analyzes its formation mechanism.Secondly,the dynamic parameters of the debris flow caused by Dongcuoqu Lake break are calculated to provide scientific reference and comparison for numerical simulation.Finally,the numerical simulation software Dan 3D is used to simulate the debris flow caused by the Dongcuoqu Lake break,which has a clear judgment and understanding of its movement process.The main research results are as follows:(1)Through field investigation and remote sensing interpretation,it can be seen that the area of the Dongcuoqu gully is 226.27 km~2,the length of the main gully is 31.44 km,and the average longitudinal gradient is 27.27‰.The terrain is high in the West and low in the East.The gully is of wide shallow"V"shape.The main gully is straight and has 20 branches,all of which intersect the main gully at a large angle.The whole gully can be divided into clear water collection area at the back edge of the gully area,circulation area and gully accumulation area are formed in the middle and lower reaches.In the basin,the adverse geological process is developed,and the scale of material source reserves is huge.The static reserves are about9536.81×10~4 m~3,and the dynamic reserves that can participate in the formation of debris flow are about 169.40×10~4 m~3.(2)A large Glacier lake is developed in the middle of the Dongcuoqu gully.According to the evaluation of the risk and stability of the dam,the probability of the glacier lake break is42%,which belongs to the medium risk;the barrier dam has a long existence time,a stable geological structure and a small risk of the overall break;the stability coefficient of the dam in the non flood season and flood season is 1.311 and 1.197,which are in a stable state;the ice and snow around the glacier lake are quickly superposed by the concentrated rainstorm in the flood season under the condition of melting,the stability coefficient is 1.057,which is in a basically stable state,it is possible to have local breakout,forming breakout flood and debris flow.(3)The movement process of the debris flow caused by the Dongcuoqu Lake break is simulated by the numerical simulation software DAN 3D,and the velocity distribution and thickness distribution nephogram of 50 year and 100 year debris flow are obtained.The simulation results are consistent with the formula calculation results,which shows that the numerical simulation method is feasible to study the debris flow caused by Dongcuoqu Lake break. |
PDF Full Text Request