Experimental Study On The Effect Of The Landslides Surge On Bridges In Mountainous River Type Reservoirs

The waves generated by landslides is very harmful.The landslide in the reservoir area may directly destroy the bridge pier on the path,and the waves generated by landslides may hit the bridge deck or act on the bridge pier to make it unstable and overturned.Previous studies on the characteristics of waves generated by landslides and its influence on the buildings in the reservoir area,but few studies on the effect of waves generated by landslides on bridges.Although the research on wave force of offshore pier structure has a long history,up to now,the wave force acting on pier structure can not be described completely and effectively.Moreover,the formation mechanism and shape structure of waves generated by landslides in reservoir area are quite different from those of ocean wind wave and water wave,so it is necessary to study the effect of waves generated by landslides on bridge in reservoir area.Taking the Fu-ling Yangtze River Second Bridge as the research object,this paper studies the effect of waves generated by landslides on the bridge through the physical model.The surge height measured in this test does not reach the bridge deck,so the main research results here are as follows:(1)It is found that the wave pressure on the bridge pier can be divided into two types: shock wave pressure and surge wave pressure.The formation reason and wave pressure form are quite different.The shock wave energy mainly concentrates on the main wave upward.The distribution law of shock wave pressure along the water depth is divided into three types: unimodal,multimodal and no peak.The power is zero near the water surface,and increases first and then decreases along the water depth.The shock wave pressure in the middle of the bridge pier is the most dangerous.(2)The D-value between wave crest and wave trough under the action of the first wave,is the pressure D-value of the first wave,can be approximately regarded as constant along the water depth.Several main influencing factors are obtained through analysis,and the influence of each influencing factor on the wave pressure is analyzed.The superposition of solitary waves is used to study the swell,and the conclusion that each particle has almost the same speed is more consistent with the distribution law of the pressure difference of the first wave along the water depth.The shock wave pressure only exists in the upward direction of the main wave,and only affects the pier on the bank,and the middle part of the pier is the most affected by the shock wave pressure.(3)The distribution law of the maximum wave pressure difference varies with the water depth.The water level in 116 cm depth shows multimodal distribution of volatility,the water level in 88 cm depth first increases and then remains unchanged with the water depth,and the water level in 74 cm depth shows a linear distribution approximately.The maximum value of the maximum wave pressure difference of the pier on the same bank is located at the static water surface,and the maximum value of the wave pressure difference of the pier on the opposite bank is located at 2m-4m below the static water surface.In the case of shallow water,the maximum wave pressure difference of piers on the same bank is greater than that on the opposite bank;in the case of deep water,the law is just opposite to that of shallow water.It is found that the width is the main factor,and the calculation formula of the maximum wave pressure difference is given.(4)The distribution law of the circumferential wave pressure of the piers at different water depth sections is different.At the 116 cm water level section(static water surface),the maximum values of the wave front,back wave surface and side appear.At the 88 cm water level(underwater 28cm),the maximum values of the shallow water layer are at the wave front and side,and at the 74 cm deep water layer(underwater 42cm),the maximum values are at the back wave surface.The influence of landslide parameters and reservoir water depth on circumferential wave pressure is analyzed,and engineering design suggestions are given.