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To research the deformation regularity of loess tunnel in reserving core soil with annular excavation method compared with other construction methods, 3D Numerical Simulation is applied and the loess tunnel of highway is taken as an example. The research results show that[1]：The deformation of surrounding rock affected by the area of core soil is small.The stress regularity of different support structure influence on the area of core soil is different. This is mainly reflected that the maximum pressure stress of primary support increases with the area of core soil’s increasing, but the minimum bending moment of secondary lining is not appeared in the working condition which the minimum core soil area is.

For the tunnel with high ground stress and soft surrounding rock, the deformation instability is the high frequency and great harm geological hazard. The supporting measure has become a important technique problem. This paper based on the Wuduxi tunnel, the characteristics of deformation and instability mechanism of surrounding rock and supporting structure are analyzed by means of the engineering geological investigation, theoretical analysis and field monitoring. The supporting measure include that using the steel floral tube to back up sidewall, adding support arch and filling foamed concrete, grouting reinforcement in basement. Finally, we use the field monitoring to check the supporting effect. The result shows that the supporting measure could achieve the desired treat effect and it has reference meaning to similar engineering.

In order to solve the problem of multi-index amalgamation on the reliability evaluation for tunnel lining with cracks, this paper based on extension theory, use matter element model theory to establish the matter element of the reliability evaluation for tunnel lining with cracks, use the dependent function to establish the relevance between matter element and reliability grade, combine the research result of the Beiru tunnel lining cracks disease to evaluate the reliability. The results show that it could consider the multi-index of the cracks to use the extension theory to evaluate the reliability of the tunnel lining with cracks, and the evaluation results are more scientific and reasonable. It is viable to use the dimensionless parameters to represent the crack geometry. In the K6, the treatment scheme is mechanical reinforcement. In the K2 and K3,the treatment scheme is surface sealing. The reliability evaluation results supply theory basis and technical guidance for the tunnel long-term health service and the disease treatment.

In order to analysis the internal relation between the matric suction change and the tunnel disease, the paper combines the Dayoushan tunnel as an engineering example, uses the mathematical, field monitoring and model shear test and to analysis the the change rule of the martic suction and the influence of martic suction on the tunnle supporting force and plastic zone. The results show that when the water content is increasing, the unsaturated loess matric suction is reduction, the force of tunnel support is increasing and the radius of plastic zone is increasing. Due to the influence of surface water infiltration, the matric suction of the around soil in Dayoushan tunnel is reduction and cause the crown settlement, landslides and lining cracks. The disease treatment mainly lies in keeping the drainage system is smooth and secure for waterproof. For the similar unsaturated loess tunnel, the research results have reference significance.

Based on a certain loess tunnel in Kelan-Linxian Expressway in Shanxi province, the influence to primary support forces by different stress release is analyzed by the Ansys FE software in the step method excavation. The analysis results can reasonably reflect the actual case of primary support forces, and can offer related reference to the selection of reasonable design parameters for primary support.

The theoretical solution to the distribution of axial force in Mindlin displacement problem and the plastic radius of surrounding rock in the condition of elastoplastic homogeneous soil are deduced. Based on the results of field test, the problem of length optimization of systematic bolt in loess tunnel was discussed from the two perspectives of mechanical characteristic under the drawing force and the axial force at the location of neural point. The obtained results will offer the technical support for the length optimization of systematic bolt in loess tunnel, which has the guiding significance in the design and construction.

For a comprehensive analysis of the mechanical properties of compound-umbrella arch in the unsymmetrically loaded tunnel entrance, we focus on the force characteristics to optimize the structure of composite umbrella arch, and improve its economic efficiency. The stresses on the bottom of pile, the pile and the steel arch were monitored, and analyzed by the finite element software. The results show that, on the bias terrain, the stress of the pile bottom is nonuniform with uneven settlement. The stress distribution is very complex, where the tensile stress appears on the pile bottom, the compressive stress takes place on the arch foot and the vault, which is not good to the stability of the overall umbrella arch. As both sides of the umbrella arch bear a large different force, the piles on both sides of the umbrella arch subject to large bending moment and axial force, which improve the stability of the tunnel entrance.

The 3D finite element simulation was adopted to study the globality stability of tunnel caused by the different excavation length of invert. Kelan-Linxian highway loess tunnels were taken as an example. The research results are shown as follows: The vertical displacement and horizontal convergence increased by the increasing of the excavation length of the invert. But the latter increase range is larger than the former. The horizontal convergence in sidewall is convergence value is greater than the level of the arch and the corner, the horizontal displacement primarily occurred in the side wall position. The surrounding rocks maximum plastic strain occurred in side wall and corner wall in 4 working conditions. The plastic zone occurred around from arch corner to wall side. In Tab. 4, the maximum plastic strain is increased by the excavation length of inverts increasing.

Based on the Pasternak elastic foundation beam theory, mechanical models solving process of pipe-roof based on the MATLAB is elaborate, and the mechanical behavior of pipe-roof reinforcement is analyzed. Results show that the pipe-roof can play an leveraged part in surrounding rock, which can make the deformation and the load around tunnel face effectively passing to no excavation section near the excavation. In pipe-roof support conditions, the longitudinal influence scope of tunnel due to excavation is about 1.3~1.5 times the excavation height.

Based on the displacement solution of Mindlin problem, the elastic solution to the distribution of shear stress & axial force is deduced under the drawing load for mortar anchor in loess tunnel. The ultimate drawing load of systematic anchor in the sidewall is measured by means of field test based on a certain loess tunnel in Kelan-Linxian Expressway, and the forcing characteristic of the anchor is analyzed. The distribution forms of the shear stress & axial force are also discussed in different soil characteristics. The obtained results will offer the theoretical basis for the design &optimum of systematic bolt in loess tunnel, which has the guiding significance in the design and construction.

Based on the analysis of the problems about the reverse circulation drilling in the practical application, such as the ability of the drilling depth, application in the loose layer, the construction of the pile hole with large diameter, three optimization programs are put forward, and evaluated in combination with the project examples of Wuhan Baishazhou cable-stayed bridge. Finally, some experiences in construction practices are given.

Based on selecting a tunnel collapse under typical conditions of the shallow-buried terrain under unsymmetrical pressure, analyzing the monitoring measurement date, using the software of finite element numerical simulation, the paper simulates the tunnel excavation in lengthwise, deduces the change laws of stress in primary support, the mechanical properties and the collapse mechanism.

Based on the excavation of portal section in Linwu neighborhood tunnel, items of the blasting vibration, vault settlement and level convergence are measured in the field construction. And according to the actual exposed surrounding rock, the finite element analytical model is established. The results of monitoring measurement and numerical analysis indicate that, under the circumstances of advance large pipe-shed roof support and varied surrounding rock, the original excavation method is not reasonable, still existing the optimization space. The construction of changed step method is feasible, which reflects the requirement of dynamic design and construction in New Austrian Tunneling Method.

According to the elastic-plastic theory, the analytical formula of plastic zone radius is established for circular tunnel in its excavation and support, and the effect of anchor support is verified based on the radius of plastic zone from the perspective of measured axial force. The influences to plastic zone by the variations of mechanical parameters and resistance of support are quantitatively analyzed. The result is of great significance to the monitoring measurement and the dynamic design and construction of tunnel.

Based on the Hejiazhuang tunnel on the Zhengzhou-Xi’an passenger dedicated railway,forcing cases of systematic anchor was studied in loess tunnel with large cross-section and forcing characteristics of systematic anchor at vault and sidewall parts were obtained; Causes that the forcing difference varies much were analyzed from the perspective of the law of radial displacement attenuation and distribution form of surrounding rock pressure，the related conclusions will offer reference value and guiding significance to the design and construction of such tunnels.

Structure performance function is established with the consideration of safety factor, taking the primary support structure as a series system and determining the invalidation model of the system, and then the internal forces of primary support are expressed by the limit displacement. The calculating analysis also takes material parameters and geometrical dimension into consideration. Based on a typical tunnel, the reliability degree of the whole system is calculated, which indicates that the reliability degree is rather smaller at a certain section of the primary support, but it can satisfy design requires of the whole system, and the tunnel stays in a safety state.

Through theoretical calculation, systemic analysis of dynamic performance of the 64m single and double line railway steel truss bridges on the expanding condition and conventional condition. Contrast and analysis the main dynamic performance parameters of bridges on the two kinds of operating condition. In 64m steel truss bridges of Shuozhou-Huanghuagang Railway application practice proves that on expanding heavy-load condition, the main dynamic performance parameters of bridges are slightly larger than conventional condition, but the variation law of vertical acceleration of mid-span is different.

Based on the undergroundHongtudistation of Chongqing Rail Transit Line VI, stress and plastic strain of surrounding rock, internal forces of supporting structure and vault settlement are calculated in different widths of core pillar. Comprehensive analyses indicate that there is an optimal value of core pillar width in the construction of tunnel with the double-side heading method. Width of core pillar, 0.3 times as large as the tunnel span, is suggested in other projects with the same construction method, which is of great significance in practices.