Applied Mechanics and Materials Vols. 353-356

Abstract: 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.

Abstract: Rock breaking mechanism and coupling effect rule between cutter tool and surrounding rock were researched, in order to resolve the shield construction problem of shield cutter tool breaking rock. The optimal broken rock cutter spacing of some common rocks was put forward, and the broken rock mechanism of multi-tool is perfected. Considering the impact of various factors,this paper obtains a new calculation method of compound shield total thrust force and cutter-head torque with mathematical and mechanical methods. The research results can be used for design of thrust force and torque, tool selection and arrange.

Abstract: The finite element software ADINA was employed in this paper to study the ventilation effect of a large cross-section cable tunnel by using a computational fluid dynamics method. The temperature and ventilation zoning inside a cable tunnel were determined according to the characteristics of the large cross-section cable tunnel. With the ambient tunnel characteristics and tunnel cross-section layout being taken into consideration, a three-dimensional model for large cross-section cable tunnels was established; the computations indicate that the main influential factors of ventilation effect of large cross-section cable tunnels are intake airflow rate, intake air temperature, exhaust airflow rate, ventilation duration, tunnel length, fire door layout, and so on. The average air velocity in the tunnel was about 60 % of the intake airflow rate. The intake air temperature has much impact on tunnel temperature distribution within a range of 30 m away from the tunnel origin, as shown by a significant cooling effect when intake air temperature falls; whereas the intake air temperature has less impact on tunnel temperature distribution beyond 30 m from the tunnel origin.

Abstract: The profile layout rationality and internal stress structure of a large-section cable tunnel and a cable-laying scheme at splicing locations were studied through full-scale model test. The full scale shield tunnel which the diameter was 6m was built on the ground. The model tests test the displacement of cable bearers, the coupling area between horizontal beam and steel ring, the coupling area between horizontal beam and steel pillar, edge beam and center beam under design loads, and the safety and reliability of an arc steel framing system that supports the cable load inside the cable tunnel during the operation stage were demonstrated. The cable-laying schemes for the cross section and straight-through-type and T-type couplings of a large-section cable tunnel were optimized through experiment on actually laid-out cables. For the section layout of a large-section cable tunnel, it is believed that the double-deck scheme prevails over the single-deck scheme, and such a cable-splicing scheme can meet the cable-laying requirement.

Abstract: According to the actual working condition of the full face hard rock tunnel boring machine (TBM), a 2-D discrete element model for breaking marble by two TBM disc cutters is established, it simulates the whole progress of cracks production and propagation under different confining stress and penetration; based on CSM prediction model, forces of two cutters and specific energy consumptions are calculated to determine the best penetration. The simulating result shows that there are three kinds of breaking modes of marble under different confining stress and penetration; As well as the trend that specific energy consumption decrease first and then increase with the penetration increases, and there is optimal penetration to make specific energy consumption the lowest each confining stress. The optimal penetration and the lowest specific energy consumption are determined when confining stress range from 0 to 40MPa according to the simulation results.

Abstract: Based on the engineering background of Tangkou in Shandong province, this thesis carries out mining-induced stress distribution law comparative study and analysis of 2313 working face which is lying below-1100 miles, using methods of theoretical analysis, numerical simulation and field measurement, and obtains the limited synergistic effect of mining-induced stress variation and working face advancing steps under the condition of kilometer-deep shaft. That is, with the increase of working face advancing steps, there will be a corresponding increase in the advanced abutment pressure peak, sphere of influence, and the distance from the peak position to the coal wall, within its limit value. The conclusion of this study have some guidance for the safe production and support design of working face in kilometer-deep shaft.

Abstract: Based on contrast analysis of tunnel surrounding rock classification method, five basic indicators were selected as evaluation factors. Evaluation matrix was constructed by uncertainty measurement theory. Weight was established by introducing drifting degree concept. The principle of maximum membership degree was choosed as evaluation criterion.Then a tunnel surrounding rock classification model was built.This comprehensive evaluation method made full use of its own parameters and evaluation standard to completely avoid the subjective influence of traditional weights determination and the sample set, making itself more objectivity and accuracy, having a strong operability. The practical engineering showed that this model applied to tunnel surrounding rock classification was feasible and had certain superiority, providing a new way for tunnel surrounding rock classification.

Abstract: Shield cutting obstacle pile directly has significant economic and social benefits compared to traditional methods, however, the corresponding cutting technology is far from mature currently in the international. Based on the construction need of cutting 14 bridge piles with the diameter of 1.0~1.2 meters by Suzhou subway shield, the preliminary scheme of cutter configuration was studied and proposed first, and then the worlds first field test of shield cutting reinforced concrete piles was carried out, the effect and rule of shield cutters cutting piles were analyzed, and the cutter configuration scheme was verified and optimized. The test results indicate that the shell cutter is fit for cutting reinforced concrete pile, its cutting effect on rebar and concrete is shear cutting; In order to make rebar shorter, we should make the rebar be cut off instead of pulled off as possible as we can. The main damage form of shell cutter is alloy cracked. Cutting side pile produces more damage on shell cutter than cutting central pile. The shell cutter configuration scheme should not only satisfy the whole cutting ability and covering the entire cutting plane, but also to be favorable to fix rebar by surrounding concrete.

Abstract: This paper studies on a certain highway project which passes through Longmen Shan fault zone, the one triggers 5.12 Wenchuan earthquakes directly. The region where the project resides is characterized by high percentage of soft rock mass, in particular the phyllite. Series of landslide have hitherto happened due to the instability of mountains along the highway which was caused by the great earthquake. Besides, since the phyllite-dominated rock was low-strength and easily soften by water, engineering disasters such as cave-in and large deformation of surrounding rock occurred frequently during the construction of tunnels located along the highway. The existing deformation control criteria fail gradually to fill the requirements of safe tunnelling. The author analyzed monitoring data from different tunnels with different cross-section types and different surrounding rock conditions, referred to relevant norms and eventually proposes new deformation control criteria based on allowable deformation and deformation rate.

Abstract: In order to explore the factors affecting the establishment of displacement control criterion for the soft rock tunnel in the earthquake region and then to provide basis for the following establishment of base values, this paper in the context of a highway soft-rock-tunnel passing through the Long-men-shan Fault, summarized the main influencing factors on the basis of the existing deformation control criterion and then proposed the main factors of deformation control criterion suited for the project after combining its own characteristics. The result revealed that: the burial depth of tunnels and the characteristic of the rock masses are critical factors affecting the deformation control criterion of the soft-rock tunnel in earthquake area; the construction methods and the cross-section dimensions are both the important factors for the deformation control criterion.