Research On Construction Progress Analysis For Concrete Gravity Dam Under Uncertainties

Affected by factors such as construction environment and human operations,the construction process of concrete gravity dams is featured with randomness.At the same time,due to the limitation of human subjective understanding,decision makers have incomplete knowledge of construction machinery efficiency,repairing time and other parameters.Therefore,there are aleatory and epistemic uncertainties in construction schedule analysis for concrete gravity dam.However,the existing uncertainty analysis research ignores the influence of epistemic uncertainty,which leads to the loss of some uncertainty information,and cannot guarantee the accuracy of the analysis results.Therefore,how to comprehensively consider the effects of aleatory and epistemic uncertainties in the construction progress analysis of concrete gravity dams and how to analyze the effects of changes in construction parameters on the uncertainty degree of construction progress are the critical issues that need to be resolved urgently.This thesis has carried out in-depth research on the above problems,and achieved the following research results:(1)Existing researches are unable to comprehensively consider aleatory and epistemic uncertainties on construction schedule uncertainty analysis.Aiming at the issue above,an uncertainty analysis method of concrete gravity dam construction progress based on modified evidence theory is proposed.The evidence theory has the advantage of solving aleatory and epistemic uncertainty problems comprehensively.However,the vertex method which is used to calculate the extreme value of monotonicity problems in the traditional evidence theory cannot be applied to the non-monotonic problems such as construction schedule simulation.In addition,the relevance of construction parameters is not considered in the traditional evidence theory.Regarding the issue above,Firstly,the genetic algorithm is utilized to modify the extreme value calculating process in the evidence theory and search the extremum value on evidence bodies.Further,the Copula function is introduced to quantify the correlation between the construction parameters and modify the joint-probability calculating method in the evidence theory as a difference.Finally,the construction parameters with aleatory and epistemic uncertainties are transformed into evidence variables.Based on the modified evidence theory method,the belief and plausibility degree are calculated to quantify the uncertainty of construcion schedule.(2)Aiming at the inadequacy that the existing researches on construction schedule sensitivity analysis cannot reflect the influence of construction parameter uncertainty on progress uncertainty,an uncertainty degree analysis method of concrete gravity dam construction schedule based on mutual-informationentropy-sensitivity-analysis is proposed.The existing researches on construction parameter sensitivity analysis mostly adopt derivative-like method to calculate the influence of construction parameter changes on the construction progress.However,it cannot reflect the impact of the parameter uncertainty on the construction progress uncertainty degree.In view of the above problems,this thesis proposes an uncertainty degree analysis method of concrete gravity dam construction schedule based on mutual-information-entropy-sensitivityanalysis.It uses information entropy theory to calculates the mutual information entropy between each construction parameter and schedule to consider the the impact of the parameter on the construction progress uncertainty degree.The sensitivity of each construction parameter is obtained by calculating the model entropy of each construction parameter,and then the sensitivity analysis of the concrete gravity dam construction parameters is realized.(3)Taking a concrete gravity dam project as an example,the above method is used to carry out an uncertainty analysis of construction schedule which comprehensively considers aleatory and epistemic uncertainties.The above method is applied to a concrete gravity dam project.Firstly,the uncertainty analysis of concrete gravity dam construction progress comprehensively considering aleatory and epistemic uncertainties is realized and the completion reliability is quantified as [0.9215,0.9792].The result is compared with the analysis result based on random uncertainty theory.It shows that the method has consistency and superiority in uncertainty analysis.Secondly,the construction parameter sensitivity analysis method based on mutual information entropy is used to compare the impact of the cable loading time,unloading time,heavy-loading horizontal speed,heavy-loading falling speed and maintenance time on the construction progress uncertainty.The sensitivity sequence is: heavy-loading horizontal speed> heavy-loading falling speed >maintenance time> unloading time> loading time.The result provides guidance for reasonable selection and effective control of construction parameters in concrete gravity dam construction.