This paper describes the observational procedure of a shallow tunnel construction in landslide area. The purpose of this research is to develop a construction method to control the displacements of the landslide and the tunnel by long face bolts and early invert closure. The practical application is proven that the both methods of long face bolts and early invert closure are effective for the tunnel construction under such a difficult condition.

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A large number of the shotcrete slopes constructed during Japan’s post-war economic boom are now more than 30 years old, and their structural deterioration is an ongoing problem. Therefore, it is necessary to accurately assess the stability and durability of these existing slopes. In this paper, we propose a technique to evaluate rock weathering and groundwater fluctuation behind the slope using a conversion analysis of seismic velocity and resistivity to porosity and water saturation of rocks. In the conversion analysis, porosity and water saturation of rocks are estimated with a non-linear optimization method based on the empirical relations of seismic velocity and resistivity to porosity and water saturation. This proposed technique was applied to a shotcrete slope along a road and verified with boring data. The porosity and water saturation estimated with the conversion analysis of seismic P-wave velocity and resistivity measured at the slope were interpreted to evaluate the rock grade and groundwater distribution of the rock behind the shotcrete slope. The interpretation was verified with the boring data to clarify the applicability of the proposed technique.

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The fluid flow and tracer transport in a single rock fracture during shear processes is investigated in this paper using Finite Element Method (FEM) and streamline particle tracking method, considering evolutions of aperture and transmissivity with shear displacement histories under different normal stresses, based on laboratory tests. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture fields, based on the laser-scanned surface roughness features of replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow tests in laboratory. The coupled shear-flow tests were performed under two levels of constant normal loading (CNL). The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements for the flow parallel with the shear direction. From the obtained flow velocity fields, the particle transport was predicted by using a streamline particle tracking method with calculated flow velocity fields (vectors) from the flow simulations, obtaining results such as flow velocity profiles, total flow rates, particle travel time, breakthrough curves and the Péclet number, Pe. The effect of normal stress on the particle transport is significant and dispersion becomes larger with increasing normal stress.

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Accurate spatial modeling of geologic structures and properties are crucial for mechanical and hydraulic characterizations of rock mass. This report presents several methods that are grouped into two categories depending on the natures of geologic data: type I for the data originated from plural populations and type II for the data that can be applied to the prerequisite of stationarity and have distinct spatial correlations. For the type I data, a spline-based method, its combination with stochastic simulation, and neural network method are demonstrated as effective, while geostatistics is certainly powerful tool for the type II data. As new approaches of geostatistics, an application to directional data such as fracture, multi-scale modeling that incorporates a scaling law, and space-time joint analysis for multivariate are reviewed briefly with case studies. These methods can contribute to Earth science and technology including rock engineering related to the problems such as repository of high-level nuclear waste and CCS (carbon dioxide capture and storage) which need the most comprehensive understandings of rock structures and properties.

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This paper describes the tunnel seismic reflection survey which has been developed by the authors in order to three-dimensionally detect geological conditions such as faults, fractured zones and geological boundaries ahead of a tunnel face using reflected seismic waves. In addition, the applicability and the accuracy of a result of this system have been validated by comparing with geological observation results at a tunnel face and the result of the drill logging system. This surveying system is called Three-dimensional Seismic Reflector Tracing System (TRT). TRT creates a 3-D isometric map of geological structures 100-150 m ahead a tunnel face and up to 30 m around a tunnel alignment. Kajima has applied TRT to about 100 times since its introduction in February 1999 to predict rock conditions ahead of tunnel faces. The images produced by TRT have been used satisfactorily to manage the risk caused by encountering unforeseen geological conditions.

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