In 1964, a Komatsu-Robbins Tunnel Boring Machine (TBM) was used to drive a pressure tunnel of water power plant for the first time in Japan. Since this first experience for TBM up to 1979, tunnels driven with TBM amount to 34 tunnels and 28 km in their total length.
The experiences on based the driving of TBM have indicated that the performance of TBM is obviously dependent on the geotechnical properties of rock formation, because they can find many case histories in which many troubles were caused by difficulties of rock formation.
In this report, the authors discuss on the possibility of application of TBM for various rock formations and the effect of geotechnical properties on the performance of TBM, based on the experiences of operation of TBM in Japan.
The geotechnical factors affecting the performance of TBM would be as follows;
1) rock stresses around the tunnel,
2) discontinuities in rock formation,
3) strength and hardness of intact rock,
4) in situ strength of rock formation, and
5) rate of inflow of ground water.
Most of rock formations where tunnels had been driven with TBM are included in the areas (I) in Fig.3. In Fig.3, the abscissa in logarithm of the square of the index of discontinuty k2, and the ordinate is logarithm of the estimated in situ rock strength k² ·σ.

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The Abo Tunnel is planning as a vehicular tunnel with a length of 4.3km from Takayama city to Matsumoto city. The area is occupied by Paleozoic clastic rocks and Quapernary pyroclastic rocks and lava. These rocks distributed in Nakanoyu hot spring, east. portal of this tunnel, were subjected to hydrothermal alteration. So following geological investigations have been conducted for the past 10 years.
1) Survey on distribution characteristics of hydrothermal altered zones.
2) Estimation of underground structure of hydrothermal altered zone by geothermal prospecting.
3) Geophysical logging of vertical and horizontal drilling hole and laboratory tests of obtained core.
The results are summarized as follows.
1) The methods of 1) and 2) are effective at early geological survey stage.
2) Geothermal zones are associated with hydrothermal solution and overheated vapour rich in poisonous gas. Geothermal gradient falls off in proportion to the distance from Azusa river bed.
3) At the same point, the temperature measured in horizontal drilling hole is mostly higher than that of vertical drilling hole because of pressure depression. Long horizontal boring is necessary to estimate a discharge of hydrothermal solution.
4) Along this tunnel, high-temperature zone is traceable for a distance of 1.5km, and there, the temperature reaches from 60°C to 90°C for a distance of 1.0km.

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Stress transfer mechanism of the jointed rock media was studied theoretically and experimentally. The discrete element model used in this study is based on the “rigid body-spring models” proposed by the second author, Kawai five years ago. In these models it is assumed that the elements themselves are rigid and they are connected by two types of springs distributed over their interface boundaries.
Using the well known Mohr-Coulomb's failure criterion and considering the effect of contact as well as separation of individual rock elements, the elasto-plastic analysis was carried out by basing on the initial stress method. It was found that the calculated results were in fairly good agreement with the results of the photoelastic analysis and that the stress distribution of these jointed rock media was considerably different from that of the compressed homogeneous continuous media.

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In this report, investigation on the soil character of strata causing difficulties in driving which should have been carried out before the commencement of the excavation by the tunnel shield have been studied by the past tunnelling experiences. As the tunnel shield driving safely in the soft ground should have equipment or measures to secure the safety of the tunnel face and to prevent the ground settlement, the soil investigation should have a great weight in the choice of the construction method. If we stands a position to prevent the tunnel face from its collapse, the blind type tunnel shield attracts our attention and also for measures to be taken for the ground settlement, the balancing of the driving power, excavated material mucking speed and opened area of the shield bulkhead is required. The difficulty in driving a tunnel by the blind type tunnel shield is caused by the presence of sand stratum or very hard clay stratum. From tunnel excavation experiences by the blind type tunnel shield or blind type mechanical tunnel shield equipped with auger, it was found that there was the occupancy limit of such strata at each part of the tunnel face. For instance, in case that the blind type tunnel shield at Soka shown in Fig. 7 encountered such strata at top part of the tunnel face, the occupancy limit was approximately 14%.
The soil investigation for the tunnel shield work are carried out at the planning and designing stage and the additional soil investigation is made at the construction stage. The items and accuracy of the soil investigation are determined according to the requirement of each stage. The tunnel shields or supplementary measures have the extent of soil suitable to each of their types or measures. Generally, as the extent of suitable soil overlaps by each types of measurs, the conclusion from the soil investigation and its result influences success of construction work. Judging from the thickness of such strata causing the difficulties in driving, if it is possible to know the presence of such strata in the accuracy of the order of 10 cm or 20 cm in thickness, no problem will be cocurred. But a careful attention should be paid to the fact that the stratum thickness may vary largely even though in a short distance.

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