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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節理の任意に発達した節理系岩盤の力学的特性を明らかにするため, 本研究ではまず応力伝達機構の立場から光弾性実験による検証を含めて, こうした不連続体の数値解析手法の可能性について論じた。
本研究ではこうした完全に離散化された不連続体に対して, 川井によって提案された剛体バネモデルを用いた離散化有限要素解析をおこなった。この剛体バネモデルは離散化された要素自身については剛とし, 要素の境界に分布する法線方向, 及び接線方向の2方向のバネでそれらが結合されているという仮定のもとに解析をおこなうものである。このため材料特性が法線方向, 及び接線方向の応力のみに関係するモール・クーロンの降伏基準に従う場合には特に有効であり, 本解析においても節理面における降伏基準はモール・クーロンの直線式に従うものとし, 初期応力法に基づいた弾塑性解析をおこなった。そして計算結果は光弾性結果とかなり良く一致し, 任意深さの節理系地盤の応力分布性状についての解析が可能であることが明らかとなった。
特に本研究では節理系岩盤の最も本質的な力学特性である, 要素境界面でのすべり及び引張破壊現象を正確に表わしうるよう, 要素の分離及び再接触を考慮に入れた弾塑性解析がなされた。そしてこうしたすべり及び引張破壊領域が節理系岩盤の応力伝達機構を明らかにするのに有効であると思われる。これら節理系岩盤の応力分布は節理形状及び拘束圧の大きさにより大きく変化し, 均質連続体の応力状態とは相当異った性状を示す。これらのことから節理系岩盤の力学的特性を明らかにするには節理系モデルの選択が極めて重要であるといえよう。

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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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