Advanced Materials Research Vols. 243-249

Abstract: Neighborhood tunnel is a special structural type with a clear distance between multi-arch tunnel and usual separated tunnel’s minimum required in the tunnel design regulations. The clear distance is small, so the interaction of two tunnels is relatively great, which will greatly influence the stability of surrounding rock especially interlaid rock. Therefore, it is very necessary to seek a safe, convenient and economical excavation method for neighborhood tunnel. Combining with an expressway neighborhood tunnel engineering practice (with clear distance 4.0m, buried depth 30.0m) withⅡ-class surrounding rock and by three-dimension elastic-plastic element numerical simulation, this paper analyzed the surrounding rock destruction approaching degree and deformation characteristics separately according to cheek pilot method, combination method, and up-down bench method of double tunnel. On the basis of the analysis, this text studies advantages, disadvantages and adaptability of each of the three different excavation methods, to provide scientific reference for design and construction of freeway neighborhood tunnel.

Abstract: When the road tunnel is excavated, the multi lining is used to being applied. In order to keep the surrounding rock stabilize and arouse the self-stability of the surrounding rock, building the first support is essential. But the slabbing often occurs near the spring line on the surface of the first lining, and because the slabbling is a common failing and not attracted our most attentions, it will develop to the crack and threaten the stability of the structure finally. This paper uses the line elastic method to analyze the mechanics that causes this slabbing phenomenon via the interaction between the surrounding rock and the first lining, and suggests the measure that escape the slabbing.

Abstract: In this research, the MTS815 rock mechanics test system , produced by American MTS co., has been conducted with transient method to study the seepage characteristics of rock under different confining pressure. Experiments have obtained the following results: with the confining pressure increased, penetration ability of water in rock decreased, but the start-up pressure gradient increased; permeability of rock decreased with the increase of effective confining pressure, which had negative exponent functional relationship between them. Based on previous researches, the study has established filtration equation which couples with stress field, temperature field and seepage field. Combined with the practical tunnel project, numerical simulated the variation characteristics of deformation of tunnel surrounding rock, pore pressure and seepage field under three fields non-coupling and coupling, numerical simulation obtained: the difference among deformation of surrounding rock, pore pressure and seepage field distribution under the coupling and non-coupling is remarkable, so it must consider the simultaneous action of fluid - solid - heat when we need to research the working of seepage law of groundwater in tunnel rock mass, and the research results enjoy important theoretical significance and practical application value.

Abstract: How to deal with a conflict between blasting vibration damage of tunnels construction with complex shallow and the efficiency has been always a difficult technical problem. Relying on the Chang Hong Ling tunnel which under-traverses the Jiangchi Town, using of field monitoring method to comparative study on the blasting vibration under different blasting scheme construction, research shows that: the up-step of non-blasting excavation + lower-bench of controlled blasting technique, successfully controls the surface blasting vibration speed within 1.5 cm/s.Then the tunnel can be constructed safely and rapidly, which provides a reference for the blasting excavation engineering in urban.

Abstract: A shallow buried tunnel was collapsed during construction. According to the actual situation of the tunnel, different collapse consolidation schemes were put forward and corresponding three-dimensional finite difference numerical models were established and analyzed using FLAC3D software. Base on the 3D Simulation results, a collapse consolidation scheme was determined and constructed. The in-situ monitoring results of vault subsidence and convergence displacement were consistent approximately with the 3D Simulation results. The in-situ measured results were in line with the specification’s allowance and show that the consolidation effect of reinforced concrete casing arch and ahead grouting method is good. This could be referenced for similar engineering.

Abstract: This paper analyzes the per-reinforcing effects of composite foundation with a shield tunnel under-passing, and tries to find the regularity in soil foundation improvement under such conditions. The paper establishes piles-soil separation model using software FLAC3D in a finite difference method and research the influence of effective pile length and effective replacement rate on ground deformation under the condition of shield-driver tunnel excavation. there does exist the optimum reinforcement range about pile length and replacement rate between the surface and the top of tunnel. Moreover this can offer reference for similar projects to a certain extent.

Abstract: Taking Nanjing Yangtze River Shield Tunnel with large cross-section (Φ14.5m) as background, the mechanical characteristic of lining structure under high hydrostatic water pressure for different segmental assembling modes is studied by large-scale similar model test. The test system can control earth pressure, uniform and non-uniform water pressure acting on lining respectively and cooperatively. The study results show that the values and distribution of deformation and internal force vary with different assembling modes. The rigidity of the whole ring for straight joint assembling is less, inducing the deformation larger and internal force smaller, which is unfavorable for waterproofing requirements. The peak positions of bending moment change with the difference of staggered joint assembling modes. Due to the smaller rigidity of K segment, the value of bending moment on that position is less. The most favorable and unfavorable assembling modes are proposed for construction design for Nanjing Yangtze River Shield Tunnel; meanwhile it can also provide important reference to the correlative project.

Abstract: Considering the poor support results of extraction drift in soft thick seam with a large angle in Dujiacun Mine, and there’s no similar design in such engineering geological conditions. Firstly, determined surrounding rock stability classification of the drift and obtained that roadway surrounding rock of this mine is type. According to the approximate range of this type roadway surrounding rock, selected parameters of bolt support, then using FLAC^3D software simulated support effect of the roadway with different parameters of bolt support, analyzed the extent of the support effect of various parameters. The simulation results show that the optimal program is φ2200mm round steel bolt in the roof andφ2500mm equal strength thread steel in the two sides. Monitoring results of ground pressure displacement of surface, load of bolt and amount of roof separation show that bolt-mesh-cable support is safe and effective.

Abstract: The choice of reasonable parameters of EPB shield tunneling in weathered granite ground is of great importance to reduce tunneling-induced effects on existing tunnels. Combined with the practice of the EPB shield tunneling below existing interval tunnels from Kexueguan station to Dajuyuan station of Shenzhen metro line No.1, the method of design and regulation of main parameters including the earth pressure in excavation chamber, the ground conditioning, the volume of the discharged soil, the grouting control and the advance speed, of the EPB shield tunneling are studied. The practice of the below-crossing shows in the weathered granite ground, it is reasonable that the earth pressure in excavation chamber is taken as 0.15-0.2 mpa, and that FER, FIR and CF of foam are taken as 8-15, 30-50% and 3-5% respectively, and that the amount of synchronization grouting is 8-10 m³ per ring along with the injecting pressure of 0.3-0.4 mpa, and that the second phase injection is employed to control the further settlement of existing tunnels when necessary, and that the advance speed is taken as 8-10 mm/min, and as steady as possible. Meanwhile, adjustments according measured data must be performed when necessary. Moreover, the real-time monitoring and a collaborative-work environment among the Parties involved in project are also very crucial to facilitate the risk management of the below-crossing.

Abstract: Underground construction will inevitably disturb the surrounding rock and soil, thus endanger the safety of underground pipelines nearby. This paper has established the damage assessment of underground pipelines resulting from underground excavation. Based on GIS platform, it also has developed the damage assessment of underground pipelines and protection decision-making system. The extent of the excavation disturbance is determined through the prediction of the sinking value of the overlying soil caused by underground excavation. The stress and strain leading to deformation of the pipeline were analyzed using numerical simulation. The damage assessment for underground pipelines according to both macro and micro aspects was suggested to provide technical support during excavation of underground engineering disaster prevention and mitigation.