Research On Quantitative Evaluation Method Of Damage Effect And Vulnerability Of Masonry Structure Under Collapse Disaster

In recent years,with the development of economy and society,the population density of mountainous areas in China has gradually increased.At the same time,China's mountainous areas,especially the southwest mountainous areas,are characterized by steep terrain,active tectonic movement and frequent earthquakes,resulting in collapse,landslide,debris flow and other geological disasters.Among them,the collapse disaster occurs frequently in the mountainous area,which has the characteristics of wide distribution,large scale and many types.It often causes damage to the roads,bridges,houses and buildings in the affected area,and even threatens the safety of residents' lives and properties.As a common type of building structure in mountain area,masonry structure is often damaged by collapse disaster.For example,in August 2017,the high-level collapse of pusha village in Nayong County resulted in dozens of deaths and the destruction of several residential masonry structures.The failure criterion of masonry structure under the impact of external objects is the key to the damage assessment,geological hazard risk assessment and structural reinforcement of masonry structure.Because the masonry structure is made of mortar bricks,which is a typical non-linear and heterogeneous material,it is difficult to quantitatively evaluate the damage of masonry structure under the collapse disaster.Therefore,how to study the failure mode,failure mechanism,damage effect and quantitative evaluation of vulnerability of masonry structure under the impact load of rockfall disaster is the key scientific problem of this paper.In this paper,the failure mode of masonry structure under the impact of rockfall is studied by outdoor test.The outdoor test is inverted by numerical simulation,and then the impact simulation of rockfall with different height on walls with different thickness and materials is carried out.Finally,the damage value curve of masonry structure and the quantitative evaluation model of vulnerability of masonry structure are established.Based on the failure criterion,the numerical simulation method is used to simulate the impact failure process of the high-level collapse of pusha village in Nayong County on the masonry structure,and the quantitative vulnerability evaluation model of masonry structure is applied and tested.Its main achievements are as follows:(1)Through the physical simulation test and analysis of stone rolling impact "12" wall and "24" wall masonry structure,it is found that when the impact energy and impact force of "12" wall masonry structure are less than 0.1kj and 16 kn,the masonry structure presents the failure mode of crack development;when the impact energy and impact force are less than 0.5kj and 50 kn,the masonry structure has bending failure but not collapse;with the increase of impact strength,the masonry structure has bending failure The structure has fallen and collapsed.Compared with the "12" wall structure,the "24" wall structure is thicker,more rigid,has strong bending and shear resistance,and has a large contact area between mortar and brick.After the masonry structure is impacted by rolling stones at a limited height,it only shows the crack development and bending failure state,and the masonry structure is relatively stable as a whole.Therefore,on the basis of outdoor physical test,only the failure mode and damage effect of "12" wall masonry structure are analyzed in the whole process,and the damage value range of masonry structure is established;while "24" wall masonry structure can only get the failure trend curve of wall under the impact of rolling stone.(2)Through the numerical simulation inversion of the outdoor rockfall impact "12" wall and "24" wall masonry structure test,and refining the rockfall impact wall model,the comprehensive analysis shows that the failure mode,damage effect and damage value range of the numerical simulation rockfall impact "12" wall masonry structure are basically consistent with the results of the outdoor physical simulation test.When the impact energy and impact force of "24" wall masonry structure are less than 0.92 k J and 73 k N,it presents the failure state of crack development;when the impact energy and impact force are less than 3.0k J and 160 k N,the masonry structure presents the failure state of bending without collapse;with the increase of impact energy and impact force,the masonry structure appears the failure state of falling block;based on the numerical simulation results,the impact speed of rolling stone is adopted Degree,impact energy,impact force,structural failure mode and failure state are indicators to establish the "24" wall masonry structure damage value curve,and the curve fitting to get the quantitative vulnerability evaluation model.(3)In this paper,the impact of the rockfall on the building caused by the highlevel collapse in pusha village,Nayong County,Guizhou Province is simulated by the particle flow dispersion element software.The dynamic characteristics of the rockfall,such as the movement process,energy,speed,etc.,as well as the failure form and damage state of the building are analyzed.The vulnerability of the masonry structure is quantitatively evaluated and the vulnerability zoning map is obtained.