Research On Risk Management Of Duration And Cost Of Long And Deep Railway Tunnel

In the railway line,the proportion of tunnel gets bigger and bigger and its length gets longer and longer,always becoming the controlling engineering of railway projects,especially southwest railway in hardship and danger mountains represented by Chengdu Railway Bureau jurisdiction.Tunnel inherent characteristics,such as the complexity of construction technology,many contingent risk factors,the complicated variety of the geologic environment,the long cycle of construction,causes the probability of project delay and cost out of control getting higher than other engineerings and the result getting more serious.If effective project management in project duration and project cost is can carried on,to a great extent,total project investment can be controlled and project duration can be guaranteed effectively in southwest railway of hardship and danger mountains.The research is valuable.Combination with field investigation into several dozens of railway tunnels under construction on the railway line and a number of experts consultation,based on independent study,summary and critical absorption,the problem of reasonable value in tunnel duration and cost and many management problems to ensure tunnel getting completed timely with quality and quantity are further researched,obtaining the following main results and conclusions:1.Based on the methods of Expert Investigation and Analytic Hierarchy Process,the ten top factors of construction delay and economic losses in tunnel were identified,such as unpredictable tunnel geological conditions,tunnel necessary engineering change,inaccurate geologic exploration data,lack of design experience,unreasonable resources allocation in site,unpunctual progress payment,self-contradiction design documents,unpunctual design drawings supply,lack of construction experience,difficulty of Land acquisition and demolition.The uncontrollable factors contained unpredictable tunnel geological conditions,tunnel necessary engineering change,meanwhile,others were controllable factors.2.Based on controllable factors of tunnel duration and cost,combination with probability theory and logic theory,a logic probability tree model of description the relationship in owner and contractors of tunnel was built.The risk prevention should take measures not only from technology,but also from organization and management was pointed out,to set up defenses,control layer upon layer and mutual coordination,striving to establish and-gate relationship.And-gate relationship should be established actively not only in owner and contractors of tunnel,but also between all departments,adjusting the cooperative relationship between all engineering participant companies,to rebuild the pattern more advantageous to risk prevention,striving to build multi-level logical relationship of large and-gate containing small and-gate.3.Based on uncontrollable factors of tunnel duration and cost,the impact on tunnel duration and cost of unpredictable tunnel geological conditions and tunnel necessary engineering change was analyzed by mathematical statistics,and pointing out these parameters approximately obeyed normal independent distribution,such as the probabilistic characteristics of drill footage per month and corresponding single linear meter cost in surrounding rock of construction team,the change probability of surrounding rock,probability,processing time and cost of geological risk accident.4.The main tunnel mileage was taked as principal axis,taking the impact on tunnel duration and cost of tunnel necessary engineering change into account and unpredictable tunnel geological conditions,the drilled footage per month and corresponding cost of a single linear meter of tunnel different surrounding rock classification,alteration probability of surrounding rock classification,probability,processing time and cost of geological risk accident,et al,were selected as random variables,and the random distribution was statistics-based.Then,based on monte carlo simulation,a multi-factor comprehensive calculation model was built for the top targets of project duration and cost.It simulated the random process relative scientifically and accurately,to change the inaccurate practice of experience estimation according to the deterministic problem,providing a effective and reliable way for determining rationally and evaluating tunnel duration and cost.5.Based on the theory of entropy,a new risk assessment method was provide for distinguishing similar risks and the evaluation was more quantitative.The tolerance on its risk(maximam tolerance loss)was considered,making its evaluation more accessible by the decision makers.6.Those existing problems of tunnel construction schedule and cost control in the present stage were analyzed,pointing out dynamic changes in tunnel construction period and cost and gradual convergent tendency with the clarity of construction parameters.Based on monte carlo simulation model tunnel duration and cost risk,the dynamic control evaluation standard of tunnel construction schedule and cost was built,to provides a new decision method for project managers by grasping the actual construction state fully in time,formulating measures dealing with deviation rapidly and accurately,and adjusting schedule and cost plan.