Application Of T-TDR Technology In Seepage Detection Of Earth And Rock Dam

Dam safety is not only related to the normal operation of the dam itself,but also to the safety of people's lives and property.Once a dam safety accident occurs,it will cause huge losses,in this regard,people should attach great importance to it.Leakage is the most common engineering problem in earth-rock dams.The leakage of earth-rock dam will not only brings hidden dangers to the normal operation of dam body,but also causes the loss of water resources.Therefore,reasonable and effective leakage detection must be carried out for earth-rock dams.In this study,different compactness and different types of soil are used to simulate the core wall of earth-rockfill dam.The creeping pump is used to provide seepage flow in the process of seepage.A theoretical model of seepage detection based on Thermo-TDR is established.Through the measurement of soil thermal characteristics and water flow flux,the different calculation models for measuring water flow flux by thermal pulse technology were compared.Finally,the upstream and downstream temperature rise ratio method was determined as the optimal calculation model.In order to study the distribution of dam seepage field,the seepage source and the flow diffusion at different locations of probe are simulated by HYDRUS-2D/3D,and the locations of thermal pulse sensor probe in dam body are optimized.The technical scheme of thermal pulse technology for dam seepage detection is improved.The main research results are as follows:(1)There is a good linear relationship between the flow flux calculated by T_d/T_u and the measured flow outflow value.Thermal pulse method(T-TDR)has a good measurement accuracy and stability for leakage detection of earth-rock dams.(2)The calculation of water flux by T-TDR is related to the compactness of soil and the type of soil.It can also accurately detect the influence of different soil compactness and different soil types on soil water flux.The soil water flux calculated by T-TDR can better reflect the seepage situation of soil under different compaction degree and different kinds of conditions.(3)The calculation of water flow flux by thermal pulse method is related to the length of heating time provided by thermal pulse method.The thermal pulse sensor is more sensitive to water flow,which can better reflect the seepage flow of actual water flow.(4)A three-dimensional earth-rock dam model is established by using HYDRUS-3D software,and the seepage model of earth-rock dam is simulated under different water pressures and different core wall materials.When the material of core wall of earth-rock dam is the same,with the rise of upstream water level,the water pressure increases,leakage field will change accordingly,and the saturation line of dam body rises,and the position of downstream seepage surface moves up.When the water pressure is the same,when the type of core wall changes from loam core wall to clay core wall,the seepage time becomes longer,and the seepage line of dam body and the position of seepage surface of downstream dam face decrease.Burying the thermal pulse sensor probe in the seepage stability field can effectively improve the measurement accuracy.Based on this,T-TDR technology can be applied to the actual earth-rock dam engineering.