| With the rapid increase of urban population and road traffic pressure due to accelerated urbanization in China,the reasonable development and utilization of underground space to alleviate traffic congestion has become a major challenge facing urban development.Urban rail transit,which is convenient and fast,has become the main direction of urban underground space utilization.However,due to the uncertainty of groundwater seepage,soil parameters,and the complexity of engineering environment,construction of subway tunnels is difficult.The artificial freezing method has become the primary method of pre-support for subway tunnel boring due to its outstanding water stopping effect,high strength support effect,and green and pollution-free construction process.In water-rich and soft strata,the temperature characteristics of the freezing curtain determine whether it can achieve the strength requirement and thus realize the water stopping and supporting effect.Previous studies have focused on deterministic analysis of the temperature characteristics of the freezing curtain,but due to the strong fuzziness and randomness of thermal parameters,the deterministic calculation cannot meet the increasing requirements of freezing method construction.Although some scholars have realized the stochastic calculation of freezing curtain temperature field,the calculation accuracy still needs improvement.This thesis creatively introduces the fuzzy random method to characterize the thermal parameters,considering both the randomness and fuzziness of the parameters.Through theoretical analysis and numerical simulation,the thesis compares the two cases with and without seepage,and derives the change law of the freezing curtain temperature characteristics in underpass tunnels under seepage conditions,providing theoretical support for the study of the evolution of freezing curtain temperature characteristics in water-rich strata.The specific work of this thesis is as follows:First,the fuzzy stochastic analysis method is introduced to characterize the thermal parameters.The relevant thermal parameters are defined as fuzzy variables,and then the fuzzy variables are transformed into random variables by using the probability density function and the normal function provided in Python,so that the fuzzy stochastic analysis problem becomes a simple stochastic analysis problem.Modeling is easier and saves computation time.Secondly,modeling freezing curtain temperature characteristics does qualitative analysis computational model to get temperature characteristics does qualitative analysis law.Because COMSOL cannot realize the random array of parameters to read the calculation,so MATLAB is used for the secondary development of the software to realize the parameter reading calculation,and at the same time reduce the amount of memory for storing the calculation results to improve the calculation efficiency.In order to obtain the change law of freezing curtain temperature characteristics more intuitively,the APP development of COLSOL software was also carried out to realize the automatic reading and analysis of calculation results.Finally,seepage conditions are introduced into the model to consider the effect of seepage on the temperature characteristics of the frozen curtain.By comparing with and without seepage,it is obtained that groundwater seepage has a significant effect on the temperature,cross-loop time and thickness of the frozen curtain,and the larger the seepage rate is,the more obvious the effect is.At the same time,the seepage flow also changes the shape and final position of the freezing curtain.By changing the seepage direction,it is concluded that different seepage directions have significant effects on the temperature variation at the characteristic points.A total of 65 figures,9 tables and 175 references are attached to this thesis. |
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