Advanced Materials Research Vols. 243-249

Abstract: Muzhailing tunnel of Lanyu railway is located in the western part of Qinling Mountain, its geological conditions are very complex. There is an extrusion fault, f16, in the Dazhangou inclined shaft, and the strata are consist of slate, sandston and carbonaceous slate. The measured geostress results showed that this location is in a very high level of geostress state, the maximum horizontal principal geostress is nearly vertical to Dazhangou inclined shaft and the measured horizontal lateral pressure coefficient is 3.79. Soft rock crushing, high geostress state, high horizontal lateral pressure coefficient and other factors led to the poor stability for the shaft. During the construction process of the shaft, the deformation characteristics are showed as strong horizontal deformation, rapid and large rate initial deformation, and long duration. According to rock lithology conditions, geostress conditions, supporting structure and dynamic construction, deformation characteristics of the shaft, the large horizontal deformation was caused by the interaction of high horizontal lateral pressure coefficient and poor geological conditions and other factors, but the main reasons of the large horizontal deformation were recognized as uneven vertical and horizontal load, extreme adverse load conditions of support structure, based on the theoretical and 3D numerical analysis. Through the analysis of the interaction of support structure and the surrounding rock, the smaller deformation in front of the working face during tunnel excavation is took place, the less stress release would be took place and the larger the ultimate load would be on the support structure. Tremendous stress was withstood by the arch crown, larger wall tensile stress was appeared at side wall, the support structure is in a poor stress state. This paper provides a theoretical basis for dynamic design and construction of the Dazhangou inclined shaft and Muzhailing tunnel.

Abstract: In this paper, FLAC^3D, the general software for geotechnical engineering project, is used to conduct two-dimensional numerical simulation for typical shallow tunnel excavation methods which include full-section method, the upper and lower step method, three-step method and CRD method etc.Effects of different excavation methods to the stability of tunnel surrounding rock are analyzed. The paper selected a subsistent tunnel as the research object. With construction simulation of different excavation methods, the paper makes comparative analysis of laws and characteristics of displacement of tunnel surrounding rock , stress distribution and size of plastic zones under different excavation methods. Study shows that: Ι.Followed by two step method, CRD engineering method and the full-section method successively, the three-step method is the best in the aspect of control of surrounding rock stress,; ΙΙ. Followed by full-section method, two- step method and the three step method successively, CRD engineering method is the best,in the aspect of size of plastic zones; Ш. Followed by three-step method, two-step method and the full-section method, CRD construction is the best in the aspect of control of surrounding rock displacement.

Abstract: Underground engineering construction in the city can not avoid bringing about perturbation on the surrounding rock and soil and then endanger the adjacent buildings’ safety. This paper fixes the data of the ground settlement and moving calculation parameters by doing a back analysis of monitoring data which comes from ground settlement caused by subsurface excavation and combing with other engineering experience. This paper predicts the ground settlement，horizontal moving，horizontal deformation and the distortion of incline and curvatural by using the probability integral method.With the numerical simulation,the paper obtains the displacement, axial strain and structural moment’s deformation law which caused by the frame structure’s settlement.The result will provide technical support for the disaster prevention and reduction of underground engineering.

Abstract: This paper proposes an analytical model to describe rock drilling processes using drag bits and rotary drills, and to induce relations among rock properties, bit shapes, and drilling parameters (rotary speed, thrust, torque, and stroke). In this model, a drilling process is divided into successive cycles. Each cycle includes two motions: feed and cutting. According to this model, drilling torque includes four components generated from cutting, friction, feed, and idle running respectively, the first three items are all proportional to the uniaxial compressive strength (UCS) when the penetration rate is constant. Laboratory tests verified the correctness and effectiveness of the proposed model qualitatively. Especially, the influence of friction on the flank face and the idle running was confirmed. Field experiments were performed. The results showed good correlation between the torque, penetration rate, and UCS. The proposed model and equations engender the possibility of eliminating useless components of cutting forces when investigating the relation between mechanical data and physical properties of rocks.

Abstract: The interval tunnel of Ningbo metro line 2 goes through the site of a car showroom project. By FEM analysis, the internal force of the tunnel is calculated under the ground upper load. From the engineering planning of the two projects, the time interval of the two projects is about six months to twelve months. When the interval tunnel begins to construct, the settlement of the foundation of the showroom is still not finished. By the analysis of consolidation rate of soil, the additional settlement of tunnel caused by the latter settlement of the showroom building is analyzed. And the safety of the tunnel is evaluated according to the analysis.

Abstract: It is very important to make reasonable construction procedure during excavating the underground powerhouse. The factors that influence the multi-layered excavation of the underground powerhouse are analyzed in this paper. And the typical multi-layered scheme is made considering of these factors. Further research shows that for the underground powerhouse that is as large as Shuibuya and Dachaoshan project, the scheme of multi-layered excavation and construction procedure can be made referring to the typical multi-layered scheme. But for those super-large underground powerhouses, some benches which are too high must be further divided based on the typical scheme. And some temporary access tunnels must be designed on appropriate benches in order to make relevant benches have no less than two working faces. Thus the speed of excavation can be improved.

Abstract: According to the blasting monitoring of the main tunnel at hidden digging section of Tuandao Second Road exiting ramp in Kiaochow Bay Cross-harbor Tunnel, the paper shows the influence of vibration on the close-spaced main tunnel. Based on the monitoring results of vibration velocity and vibration frequency in the vertical, horizontal radial and tangential direction, we find that the maximum value of vibration velocity in the main tunnel appears in the range of 5-20m in the rear of the ramp corresponding work face. The magnifying effect of the vibration velocity in the rear of the work face is more obvious than the front in the horizontal radial and tangential direction, and the attenuate effect appears in the front in the vertical direction. The attenuate effect of horizontal radial vibration frequency in the main tunnel appears in the rear of ramp work face. The attenuate effect of vertical frequency in the excavated section is more obvious than the unexcavated.

Abstract: The concept of karst water burst flood is first proposed in Maluqing tunnel construction. The paper analyzes repeatability intermittent hysteresis of karst water burst flood. Work out the plan that long-hole grouting based on these characteristics, and evaluat the safety and stability of water stop cement according to Darcy’s law and site actual measurement.

Abstract: Secondary lining of Longxi mountain tunnel damaged seriously during Wenchuan earthquake. To interpret the seismic failure reasons about secondary lining, the analysis adopts mechanical calculation and numerical simulation method. As a result, it was found that the bearing condition of secondary lining has an obvious spatial effect when the local loads act on the tunnel. Due to the inertial force of local load exerted by vertical seismic action, the secondary lining tends to be cracking, spalling, or even collapse.

Abstract: The determination criteria and methods are summarized for the reasonable supporting opportunity which is obtained from the numerical calculation of GeoFEM. It is the limit state of surrounding rock when the second lining undertakes 10 percent of load in Ⅳ grade rock(buried depth 121m), and the surrounding rock with burial depth 43meters reaches its limit state when the second lining bears 5 percent of load in Ⅴ grade rock. The reasonable supporting opportunity will be obtained from those two limit states with the criteria.