Tunnels in the operation period are faced with different types of diseases, such as lining fracture, lining containing voids and lining leakage. In this paper, the common tunnel lining diseases are classified and ground-penetrating radar (GPR) is adopted to detect the tunnel lining diseases rapidly and nondestructively. The finite-difference time-domain (FDTD) method is used to carry out numerical experiments on GPR detection forward modelling and backward projection imaging. An interpretation criterion of GPR detection was established on typical lining diseases. Based on the dielectric differences between before and after grouting of tunnel lining, GPR is introduced into the evaluation of grouting on leakage in tunnel lining, and the numerical simulation of grouting effect is carried out. It can be concluded that GPR imaging can well-identify the dielectric changes before and after grouting and evaluate the grouting reinforcement effect more intuitively. Finally, this method was applied to a practical case in Kaiyuan tunnel, China. This paper provides an alternative way to detect tunnel lining leakage in operation period and a reference for the evaluation of structural defects reinforcement in underground engineering.

Scientific site selection can significantly reduce construction risk and cost during construction of underground petroleum storage. Based on the analytic hierarchy process (AHP) theory and ideal point theory, a new site selection model for large underground petroleum storage is established in this paper. Nine indicators are selected as evaluation indices, including joint development, natural water-sealed condition, rock mass strength, in situ stress, environmental ecological vulnerability, regional stability, technical and economic conditions, topography, and meteorological conditions. Based on AHP theory, the weight of each evaluation index is determined. Secondly, the positive and negative ideal solutions of these evaluation indices are determined using ideal point theory. The ideal point evaluation function of each evaluation index is built to calculate the degree of closeness for the evaluation samples. Finally, the accuracy of the model is verified by using the model to evaluate the first underground petroleum storage project in China. The results show that the first six indicators are main controlling factors, and the sum of their weight is 88.3%. The result of the evaluation site level is good (II), which is suitable for construction. Moreover, the feasibility and accuracy of the evaluation criteria, and evaluation method is verified after cooperation with the power coefficient method and expert evaluation method. The research results can provide some references to the site selection of similar key projects.

Water inrush is a serious geological hazard in the deep buried tunnel construction in karst areas. Lining and grouting ring are often built to prevent tunnel from water inrush. The estimation of external water pressure and water inflow is of great significance to the structure design of lining and grouting ring. In this paper, the axisymmetric analytic solutions of external water pressure and water inflow were derived for deep karst tunnels under saturated steady-state flow conditions. A simplified formula for the reduction coefficient of external water pressure was established. This paper analyzed the changing rule of water inflow coefficient and the reduction coefficient of external hydraulic pressure on linings, which varies with the parameters of lining and grouting circle. The rational and available coefficients of grouting circle in karst deep buried tunnel construction are drawn: the grouting ring thickness is 6 m and the hydraulic conductivity ratio of surrounding rock and lining is 100. In addition, the accuracy of the simplified formula was verified by the comparison of analytical solution and numerical analysis. This study provides a reliable calculation method for water inflow and lining water pressure of the deep buried tunnel and have certain reference value for the structural design of deep buried tunnel to reduce water inflow and ensure construction safety.

Springs are a source of drinking water and a famous tourist attraction in Jinan, China. In this paper, a multi-index evaluation method was proposed based on a normal cloud model. This model is new graphic model, which could synthetically picture the randomness and fuzziness of concepts. Ten parameters were selected, and water quality was classified into five levels. Three numerical characteristics were calculated, and the weights were assigned by an integrated weighting algorithm. The uncertainty of each spring was calculated by a cloud generator and the integrated certainty grades of water quality were determined. To ensure the accuracy of the normal cloud model, the proposed method was used to assess the water quality of springs in Jinan, China. The results obtained by the proposed method were compared with that of the other four methods. The results obtained by different methods are highly consistent. The proposed cloud model-based method can reflect the water quality level and provides a practical guide for water quality evaluation, as demonstrated in Jinan springs.