Research On The Basic Theory Of Major Geotechnical Engineering Risk Assessment

There are some uncertainties in the construction and operation of major geotechnical engineering,which lead to the risk of major geotechnical engineering.Because the risk assessment can provide important basis for the scientific decision-making of the major geotechnical engineering construction,it has received extensive attention from the academic and engineering circles,and it is the key topic of the current research in the field of geotechnical engineering.For half a century,geotechnical engineering has carried out a series of research work in this field,and achieved some valuable research results.It should be emphasized that the research on the risk assessment of major geotechnical engineering as a scientific problem and serving the construction decision of the projects is late.At the same time,the risk assessment of the major geotechnical engineering is also a complex problem involving multidisciplinary.It is very challenging to carry out the research in this field.This paper mainly studies the basic theory of the risk assessment of major geotechnical engineering,and carries out a series of basic theoretical studies on the basic concept of engineering risk,the framework of risk assessment,risk factors analysis,risk assessment methods,and the acceptable risk criteria.The main research results are as follows.1.The basic concept of major geotechnical engineering risk is studied in this dissertation.This paper systematically reviews and summarizes the evolution process of risk definition.The concept of risk is summarized and analyzed from the philosophical level.The ontological status of risk definition is argued.The definition of risk is given as follows.Risk is a situation which produces uncertain consequences for something of human value.On the basis of the different risk perceptions of realism and constructivism,the paper puts forward the concept of the continuum of the risk theory.Based on the analysis of the sources and classification of geotechnical engineering uncertainty,according to the definition of risk given in this paper,the risk of major geotechnical engineering is defined as the potential loss caused by engineering accidents to life,property,environment,society and as well as engineering itself.2.The research on the framework of major geotechnical engineering risk assessment is carried out.Based on the discussion and analysis of the current status and background of major geotechnical engineering risk research,a theoretical framework and a discipline system combining risk science and geotechnical engineering is constructed.The purpose is to combine the risk science theory and method with geotechnical engineering to solve the content and framework issues of major geotechnical engineering risk assessments.This paper divides the risk assessment of major geotechnical engineering into four phases: establishing context,risk identification,risk estimation and risk evaluation,and gives the basic process of engineering risk assessment.According to the basic risk assessment process,the research content of major geotechnical engineering risk assessments is proposed,including the connotation of risk assessment,risk factor analysis framework,risk assessment criteria,and risk assessment method.The dissertation argues that risk assessment of major geotechnical engineering is the primary stage of application of risk science in geotechnical engineering.The major risk-based geotechnical engineering design theory is the advanced stage and direction of development of risk science in geotechnical engineering.The paper considers that major geotechnical engineering should be changed from performance-based design to risk-based design.3.The dissertation conducts research on major geotechnical engineering risk factor analysis and risk assessment methods.The paper established an analysis framework for major geotechnical engineering risk factors,including external hazard factors and vulnerability factors within the project,as well as the vulnerability of objects of hazard effect due to engineering crashes.Combining the three questions that the risk assessment must answer,this paper systematically discusses risk identification methods,risk probability estimation methods,and loss estimation methods for major geotechnical engineering failures,risk estimation methods,and risk reduction assessment methods for major geotechnical engineering.Among them,the geotechnical engineering risk probability estimation uses the reliability method and the vulnerability estimation method,and gives a variety of risk probability estimation methods under the failure and instability failure modes.The loss estimation methods mainly include the basic model of loss estimation,life loss estimation,economic loss estimation,and social and environmental impact estimation methods.According to the basic national conditions of our country,we will explore ways to establish a monetization method for risk estimation of major geotechnical engineering.3.major risk factors analysis and risk assessment methods for geotechnical engineering.The framework of the risk factors analysis of major geotechnical engineering is set up,including the external risk factors and the vulnerability factors in the project,as well as the factors affecting the vulnerability factors of the regional disaster bearing bodies.Combined with the three questions that the risk assessment must answer,this paper systematically discusses the risk identification method,the risk probability estimation method,the loss estimation method,the risk estimation method and the evaluation method of reducing the risk.Among them,the risk probability estimation of geotechnical engineering is based on the reliability method and the vulnerability estimation method,and the risk probability estimation methods under various failure modes are given.The loss estimation method mainly discusses the basic model of the loss estimation,the estimation of the loss of life,the estimation of the economic loss,and the estimation of the social and environmental impact.The method of risk estimation is focused on the analysis of the value method of life statistics.Combined with the characteristics of China's national conditions and major geotechnical engineering risks,the risk estimation method of China's major geotechnical engineering in the form of unified currency is explored.4.The dissertation conducts research on acceptable risk criteria for major geotechnical engineering.The paper first elaborates the concept of acceptable risk and its criteria.Based on the questionnaire survey,the proposed values for acceptable risk criteria for life,economy,society and environment in major geotechnical projects in China are suggested with reference to the existing research results at home and abroad.The recommended values for the personal life acceptable risk criteria for major geotechnical engineering: individual tolerable risk standard is 10-5/year,acceptable risk standard is 10-6/year,negligible risk standard is 10-8/year.The FN curve(accumulated cumulative probability of life loss)of major geotechnical social life-acceptable risks is plotted,relevant parameters of the curve are suggested.The FD curve(economic loss accumulation Probability curve)of economically acceptable risk criteria for major geotechnical engineering is plotted,and gives the recommended values for the relevant parameters of the curve.Public decision-making cost standard for reduction of life risk is calculated based on the of life quality index(LQI)and value of statistics life(VSL)model.Grade standard of social stability and environmental acceptable risk is proposed.5.An case analysis of earthquake risk assessment of high earth rock dams is carried out.by collecting,collating and analyzing research literature published by scholars at home and abroad,seismic hazard,earthquake damage forms and seismic vulnerability of high earth-rock dams are analyzed.According to the major geotechnical engineering risk assessment process,methods and acceptable risk criteria,the seismic risk of a high earth rock dam is evaluated.Establishing context,risk identification,risk probability estimation,destruction loss of engineering self are studied.Disaster losses in the downstream area of the dam break Estimated under conditions of earthquake dam-break.Two failure modes,dam instability and permanent deformation,are selected to carry out the estimation of seismic risk probability of high earth-rock dams.The failure probability is estimated by the safety rate of relative reliability method for the dam slope instability.Earthquake vulnerability analytical method of relative subsidence of the dam roof is adopted for the failure mode of permanent deformation of the dam.The probability curve of engineering seismic fragility under different ground motion acceleration is plotted.The direct economic loss of a high earth rockfill dam is evaluated according to the index of vulnerability.In the case of a high earth rock dam,the life loss,economic loss and social and environmental impact on the downstream impact area of a high earth rock dam are roughly estimated.According to the acceptable risk criteria for major geotechnical engineering,the conclusion of earthquake risk evaluation for a high earth rock dam is drew.