Applied Mechanics and Materials Vols. 170-173

Abstract: To keep the stability of tunnel’s surrounding rock, and control the deformation of surrounding rocks and reduce the maintenance cost of tunnel in maximum, this article did the following aspects. Aiming at large pressure , large deformation , bad maintenance state in deep coal mine tunnel , joint cable anchor support technology is adopted , and the coordination deformation of tunnel is accomplished through anchor net-surrounding rock and its coupling with the anchor cable .Through the theoretical calculation and numerical simulation of cable anchor coupling support ,we determine reasonable technology coefficient of bolt supporting and verify the correctness of support coefficient by field observation.

Abstract: Deformations of the tunnels may results in settlements of the ground surface. Based on the characters of deformation of twin closely adjacent tunnels excavated, a basic deformation mechanism of two parallel tunnels constructed close together was present, which is not uniform but oval-shaped ground deformation pattern and represent the ground loss occurred during construction of the tunnels. An improved convergence model of the tunnel boundary for twin closely adjacent tunnels and the related expressions are proposed. Using a computer package FLAC2D, the certain given deformations as the boundary condition were applied to the boundaries of two tunnels, and the surface settlements caused by the excavation of two tunnels were obtained. It is found that the results match well with the measured field results.

Abstract: The state of art of tunnel earthquake damages and tunnel earthquake damage mechanism are briefly introduced in this paper. According to tunnel’s traffic function and damage descriptions based on the investigation, tunnel damages are divided into five grades: no damage, minor damage, moderate damage, major damage and collapse, and their corresponding damage index range and characteristic values are defined. The influence of tunnel materials in Kobe earthquake and Chi-Chi earthquake are collected in this paper, and the damage grades are determined based on the performance in the earthquake. After comparative analysis, the seismic intensity, overburden depth, rock classification, distance to faults and the tunnel length are chosen as the seismic damage influence factors. A formula for tunnel seismic damage evaluation is deducted using these factors and the least square method and with the modification of construction time, seismic fortification intensity and portal stability. The damage of four tunnels is evaluated using the derived formula, and the results are the same with that of static and dynamic methods. It shows that the method provided in this paper is effective, reliable.

Abstract: During the tunnel excavation construction, the internal stress of surrounding rock surface will release to zero immediately, and the displacement of the surrounding rock surface increases slowly because of the delayed strain of the rock material. Set the stress of the surface is easier then set the strain of the surface while numerical simulation of excavation in FLAC3D and other software. Based on the rock mechanics and excavation process, combined with on-site monitoring of the displacement data, use the FLAC3D software to establish study examples, use Genetic Algorithm optimize the weight and bias of the neural network, analyze the release rate of stress of surrounding rock under a reasonable construction time. It can provide the reference data for the tunnel design, construction and the numerical simulation analysis during construction under the similar conditions.

Abstract: Beijing East Road No.1 tunnel in Guiyang city has the most complexity in arround, so prediction and control the blasting vibration is the most important task. In order to improve the accuracy of the prediction of the blasting vibration to mitigate the possible hazard in tunnel construction, studied on method of predicting peak particle velocity (PPV) using support vector machine (SVM) and established regression prediction model based on SVM. Comparisons between the predicted PPV using the empirical equation regression and SVM was made, find that the SVM gives much better prediction of PPV than does the empirical equation regression.

Abstract: Because of the Limited urban space and the development of transport, underground space development, especially the metro construction, is vigorously developed in many cities. Subway passing through the existing building inevitably may cause the settlement and deformation of the buildings and their foundations. Therefore, research on the influence of tunneling on existing buildings has important significance. In order to study the influence of tunneling on settlement of existing pile foundations, soil elastic modulus, cohesion, friction angle, tunneling sizes, distance between tunnel opening boundaries and existing pile foundation etc. are discussed as analysis factors in this paper. The calculation schemes are designed based on orthogonal design, and then the influence of tunneling on existing buildings is researched according to the numerical calculation model which is established by the finite element software. Finally, the sensitivity of pile foundation settlement to various factors is analyzed according to the results of simulation analysis. we can draw the conclusions: the influence of tunneling on settlement of existing pile foundation is positively correlated with tunneling sizes, and is negatively correlated with soil parameters and distance between tunnel opening boundaries and existing pile foundations; The settlement of pile foundations can be effectively controlled by application of composite anchor isolation piles around the existing buildings piles, but with the increase of soil parameters and distance between tunnel opening boundaries and existing pile foundations, the strengthening effects are decreased; soil elastic modulus and excavation sizes are the key impact-factors of pile settlement within the distance of 5m between tunneling boundaries and existing pile foundations, which have extremely remarkable effect on the subsidence of pile foundations.

Abstract: The construction time of secondary lining in loess tunnel has been the focus of attention in the tunnel field, but no specific quantitative discriminant index of the construction time of the secondary lining has been applied. Relying on the Wofosi tunnel of Zhangjiakou-Zhuolu highway, based on the deformation characteristics and deformation rate analysis of the crown settlement and surrounding convergence, proposed that the stability of basic rate as the indicators of construction time of secondary lining, determined preliminarily the construction time of secondary lining by optimizing the regression model, combined with the characteristics of the rock pressure and pressure distribution state along the hole to determine the best construction time of secondary lining

Abstract: Prediction of tunnel surrounding rock displacement is a hot topic. To accurately predict the displacement of tunnel surrounding, we put forward three exponential smoothing method and describe its basic theory. Based on the measured displacement of a tunnel monitoring sections in Northwest area, compared with traditional regression analysis and grey model as GM (1, 1) to predict the displacement, the results show that the average error and variance about prediction of displacement using three exponential smoothing method is minimum. This method is suitable for the prediction of tunnel surrounding rock deformation and can be applied to practical engineering.

Abstract: With large-scale construction of subway lines, the influence of subway excavation to the frame structure has been an common problem to be solved. Finite element software was used to create three-dimensional model of the subway with different horizontal distance to the frame structure, and variation of frame structure’s bending moment, axial force, shearing force caused by subway excavation is obtained to analyze. The results will enable engineering staff to have a more comprehensive understanding on this issue, and provide guiding significance for solving similar engineering problems to some extent.

Abstract: Based on the ABAQUS software, set up the tunnel and adjacent buildings and their pile of calculation models, analysis shield construction on the deformation of adjacent buildings and pile foundation. Analysis shows that the construction of the tunnel shield leading to surface subsidence, causing deformation of the framework structure and underground pile. Also shows Shield construction on the impact of adjacent buildings and underground pile deformation is integrally related.