Study On The Developmental Characteristics And Hazard Model Of Collapse And Landslide Hazards In Yangtze Upstream Channel

The Yangtze River Waterway is the main artery of water transport in China,but it has always been threatened by various geological disasters,especially in the upper reaches of the Yangtze River.This paper uses theoretical analysis and numerical simulation methods to study the main development features and hazard model of Collapse and Landslide Hazards in the Yangtze River.The main research results of this paper are as follows:(1)Through the analysis,summary and consolidation of the collapse-slip disasters in the four sections of the fairway of the upper reaches of the Yangtze River in the course of the natural waterway,backwater fluctuating area,the annual reservoir channel,and the inter-dam channel section,it was found that there are a series of folds,faults,and ancient landslides were found in the variable backwater channel segment.When there was a large-scale rainfall and more obvious changes in the river level,and the collapse and landslide hazards are easily triggered.The channel section of the reservoir area in the perennial reservoir often presents soft and hard phases,or a thin layer of hard rock layers in hard rock layers.When encountering heavy rainfall,it is easy to slide along the contact surface of sandstone and cause instability.The channel section between the two dams is affected by the water level in the reservoir area.The area contains some loosely-packed layers in modern times,with heavy rainfall and Rapid changes in the water level of the reservoir can easily lead to traction disintegration or slow-slip deformation damage.In general,in the various waterway sections of the upper reaches of the Yangtze River,the channel sections in the perennial reservoir area are the most frequently occurring sections of landslide hazards.(2)Through the analysis of the collapse of each channel segment,taking the channel section of the perennial reservoir area in high-risk areas as the research object.According to the sorting of disasters,it is found that the collapse disasters are more common in the “V” shaped section channel,and landslide disasters are more common in the “U” shaped section channel.Therefore,Flow 3d software was used to simulate the collapse disaster in the “V”-shaped section model,and the landslide disaster simulation was performed in the “U” section model.According to the "Inland navigation standards" and other data,the critical wave height and velocity values are selected.The channel area where the wave height and velocity exceed the navigation limit value is called the navigation channel segment.The vertical distance from the disaster site is called the navigational distance.In the same way,the fairway sections with wave heights and flow speeds that impede navigation will be hindered.The vertical distance from the disaster site is called the hindrance distance.(3)The degree of influence of the collapsed bodies on shipping was studied when the amount of entering rivers and the collapse height were different.Select the most easily collapsed height H=600 m,and simulate the different broken and hindering distances generated by the different amount of the collapsed bodies on the waterway,and make the curve diagram of the relationship between the amount of collapse and the sailing distance and the hindrance distance;select the characteristic amount,the simulations were conducted to obtain the relationship between the breakage and hindrance distances produced at different collapse heights,and the relationship between the collapse height,the disconnection distance,and the hindrance distance.According to the above-mentioned graphs,it is possible to predict the possible impact on the fairway after a sudden collapse of the navigation channel section of the reservoir area.The relevant authorities can take prohibited measures for the navigation section within the distance of the broken navigation to ensure shipping safety.According to the map of the distance between the collapse and the sailing,if the collapse height is the most likely to collapse at a height of 600 m,when the amount of collapse is more than 20,000 m3,the navigation channel will be affected by the disruption of navigation,and the relevant agencies can take bans.To ensure the safety of the vessel,if the amount of collapse is less than 20,000 cubic meters,only the navigation channel will be hindered,and the relevant departments may remind the vessel to drive cautiously.(4)The degree of impact of landslide hazards on shipping was studied when the amount of rivers entering the river and the height of the landslide center were different from the water surface.Using Magics software to cut the landslide hazard body to make the simulation process closer to the actual situation,select the center height of the most easily landslide H = 350 m,and simulate that the landslide body with different amount will break off the waterway and hinder the distance,and make a landslide The curve of the relationship between the volume and the sailing distance and the hindrance distance;when V=20,000 m3 is selected as the feature volume,the distance between the broken and hindering distance generated by the center at different heights is simulated,and the height of the landslide and the sailing distance are calculated.Obstruction distance relationship curve.Similarly,according to the above-mentioned graphs,it is possible to predict the impact of certain landslide disasters that may occur after the sudden occurrence of the waterway,and the relevant departments can adopt the no-bailout measures for the navigation section within the distance after the disaster,so as to ensure shipping safety.According to the maps of the landslide volume and the sailing distance,if the height of the landslide is the easiest landslide height of 350 m,when the landslide volume is more than 50,000 m3,the navigable channel will be affected,and the relevant departments can take flight restrictions.Measures to ensure the safety of the vessel.If the volume of collapse is less than 20,000 cubic meters,only the navigation channel will be hindered.The relevant authorities may remind the vessels to operate with caution.