Study On The Buffer Property Of Roof Panel With Sand And Soil Cushions Under Rockfall Impact

Rockfall is a natural disaster which often happened in mountains with geologic structure developed.Rockfall hazards is occurring suddenly,strongly random and huge destructive.It seriously threat the safety of people's life and property.With the deep implementation of western development strategy and the construction of "One Belt and One Road",there will be a large number of infrastructure in the mountains,so the rock fall effective engineering protection measures must be taken.This paper conducts a research for cushioning protection under rockfall impact,and has an important application value and theoretical significance.This paper gives a comment on overseas and domestic rockfall research Status.In view of rockfall impact protection of the building roof,put forward four kinds of protective buffer solutions:1)Pure sand layer protection;2)Pure soil layer protection;3)Composite protective with bottom placed XPS plate and upside covered of sand;4)Composite protective with bottom placed XPS plate and upside covered of soil;Using the subject platform of Research on failure mechanism and protection measures of power special structures damaged by rockfall impact for rockfall impact test.Laying different buffer material on the concrete slab,Changing the thickness of sand cushion or soil cushion,through the different heights of rockfall impact test analysis,to obtain rockfall impact acceleration process and concrete slab dynamic response process of reaction force.Via analyzing the test data,get the duration of impact,peak,impact change form with time passed,etc.important results.Contrast and analysis the buffer effect of different protective buffer plans,to provide the reference for the design of roof panel's protection.Compared with the existing literature's impact algorithms results and the test results,then summarizes the applicable conditions of the algorithms and put forward the improvement opinions.The main conclusions of this paper is as follows:(1)Sand(soil)impact acceleration peak value and impact force peak value will increase with the decrease of sand(soil)layer thickness when a hit from the same height of rockfall.The growth trend of Rockfall impact acceleration peak value and concrete slab reacting force peak value are approximate exponential growth when the cushion layer is sand,but their growth trend is relatively slow when the cushion layer is soil.(2)The four angle impulse from the plate are consistent when The sand(soil)cushion layer is same thickness and hit from the same height of rockfall.It should focus on the rock fall height on the influence of the impact process when falling rock at high drop height,so we can borrow this exponential growth model,to estimate rockfall impact energy of a larger drop height.(3)In the process of impact resistance,impact energy can be significantly consumed depending on the XPS plate's deformation and breakage.Overall,in the same condition,the buffer effect of pure soil cushion layer is better than the pure sand,it is recommended to use buffer layer in the form of soil + XPS plate combination.(4)The relevant domestic impact method to calculate the impact for rockfall is in fact the average impact,so the calculation result is small than measured value,so it is dangerous for practical engineering design,recommend use suitable magnification coefficient to improve.Due to Road community of Japan and Switzerland Labiouse etc.recommended method are derived from experiment,so the result of the biggest impact is more practical.(5)In exploring the most concerned rockfall biggest impact,recommend to use Road Community of Japan and Switzerland Labiouse algorithm,and pay attention to some important parameters'(such as lame constant,the soil's deformation modulus)selection,and need to pay attention to parameter conversion in the different thickness of cushion layers and different rockfall impact Angle.