Applied Mechanics and Materials Vols. 353-356

Abstract: In order to investigate the influence of tunnel excavation on adjacent rigid-flexible pile bearing horizontal load，many three-dimensional numerical analysis were conducted by altering the pile-soil stiffness resulted from the change of elastic modulus, radius, and length of pile. Many useful conclusions can be drawn. The longitudinal shear force and transverse bending moment of pile increase with the increment of longitudinal horizontal loads and pile-soil stiffness ratio for the pile of constant length. Therefore, different measures must be executed to protect adjacent piles with different stiffness during tunneling. This study can provide some references for the design and construction of tunnel.

Abstract: Three kinds of frozen soils were tested for artificial ground freezing (AGF) project in the tunnel construction of Stonecutters Island Sewage Treatment Works, Hong Kong. Triaxial shear test was conducted to obtain shear strength of frozen soils. From the test, Mohr circles and their envelopes were obtained. According to Mohr circles, shear strength of the three soils was gained. Comparing the three soils, we found the potential weaken layer which might cause failure in the construction. All the parameters obtained can be used in design and construction of AGF practice.

Abstract: Immersed tunnel was constructed in the year 1910 at the first time. The next few decades, there were more than one hundred immersed tunnels constructed in the world. Zhoutouzui Immersed Tunnel of Guangzhou City is the seventh underwater tunnel in Chinese Mainland. It is one concrete tunnel with rectangular cross-section which is variable because of the constraint conditions at overpass. It has distinct feature in Chinas tunnel design. The overall design and technical characteristics of Zhoutouzui Immersed Tunnel are described in detail.

Abstract: Artificial ground freezing method (AGF) was applied in cross passage constructing of line 1 and 2 of Wuxi Metro. Mechanical properties of frozen soils such as uniaxial compressive strength, modulus of elasticity, Poissons Ratio, frost heave rate and freezing point are prerequisite for design and construction of AGF. In order to obtain the parameters mentioned, laboratory tests were conducted. One was the basic geotechnical test. Another was the frozen soil test.

Abstract: Based on joint statistics from the in-situ survey, using numerical simulation technique of joint network (Monte-Carlo method), the calculation model of fractured rock mass is generated. Underground seepage discharge filed in fractured rock mass surrounding storage caverns is analyzed by using distinct element method. The result of simulation has shown good agreement with surveying data. Two cases have been simulated that is water curtains is installed and is not installed. Water pressure distributions in joints are investigated in these two cases. It is shown that in the case without water curtain the groundwater in joints which locate the upper of underground caverns is drained out and water sealed conditions is completely unrealized. When water curtain pressure is set at 0.3MPa, can underground water seal the storage caverns.

Abstract: Through the mould contrasting experiments the carrying capacities and deformation effects of surround rock with different underground roadway arrangements are studied in this paper. On the basis of experiment measuring results the bearing capacities and strains of surround rock moulds in different stratum roadways and arrangement positions are obtained. It is shown that underground roadway positions in weak rock stratum can bring about more decrease in surround rock bearing capacities and the positions below weak stratum can have high bearing capacity under the high ground pressure actions. The roadway horizontal space enlarging one times may increase more 25% bearing capacities of surround rock for rock or weak stratum roadway. The dislocation arrangements of roof roadway with below weak stratum roadway can improve about 41.5% bearing effects and have a little deformation of surround rock. The research conclusions are important significance of conducting for reasonable designing underground roadway engineering.

Abstract: Coal mine has stepped into deep mining period in China, in which the ground pressure is great, the stability of the surrounding rock is poor and roadway is seriously destroyed. 3302 trick roadway of Zhaolou coal mine is the kilometers depth roadway, under the condition of original supporting, the roof settling amount and the surrounding rock deformation were large, which made bad effect on safety production. The surrounding rock failure region was monitored by borehole televiewer and ground penetrating radar, and the loosening failure law was analyzed. The scheme of high prestressed anchor beam was proposed according to the detection results, the crack distribution of surrounding rock and the stress of blots and anchors of original scheme and optimized scheme were analyzed by UDEC. The results of numerical simulation and field monitoring showed that increasing prestress of blot and anchors was better for the control of roof separation in anchorage zone and maintaining the integrity of roof, and high prestressed anchor beam can effectively improve the effect of surrounding rock control in roadways.

Abstract: Columnar joints are native rupture structures which are ordered columnar forms in basaltic lava. The cracks and joints inside them are well-developed which lead to the weak self-supporting ability after excavation. At present, loose and collapse of columnar rock mass are the main problem in the hydraulic diversion tunnel. Based on field observation and test, this paper studied the failure characteristics of columnar joints in the diversion tunnel and simulated the failure mechanism. Based on this discussion, optimized support measures have been taken to ensure the safe construction of the diversion tunnel.

Abstract: In order to determine the long-term mechanical properties of surrounding rock of salt cavern gas storage, long tri-axial creep test studies on rock salt of the field were carried out. Based on the test data, long-term strength of rock salt was determined, and comparatively analysis was conducted combined with of the instantaneous test. The study results show that: Considering the axial strain, radial strain and volumetric strain to determine the long-term strength of rock salt can ensure reliability of the results. Under the same condition, the less salt content, the value of long-term strength is higher. Tri-axial creep process has a different effect degree between cohesion and internal friction angle; it is more sensitive to cohesion. The strain limit should be considered for the stability analysis of multi-bedded salt cavern gas storage construction and pay more attention about the mechanical properties of the interlayer parts. The study results provide references for researching the surrounding rock long-term mechanical properties of salt cavern gas storage.

Abstract: The concept of "tunnel karst disease risk estimation" is put forward for the first time, which is applied in advance geological forecast of Shajinjie tunnel. This method can help us recognizing the main hole advanced prediction work to improve the forecast work pertinence. In the forecast method, it takes the head in integrating the surface high-density electrical method with the georadar method, which improves the forecast accuracy of serious karst disease. The actual excavation results show that the advance geological forecast results meet the actual situation highly.