Framework of the present geological structure around Osaka was formed by the Quaternary tectonic movement, called“Rokko Movement”, becoming prominent since about 0.5×10⁶ years ago. The movement is known to have affected even the Cenozoic sediments.
Many large construction works have been done in the uplift district around Osaka on the national growth in recent couple of the decade. Many investigations have been done on new outcrops exposed by construction works. But there are few applied geological studies about various phenomena concerning with faults in sedimentary blankets. The author has offen observed imbricated sheared zone-which is ref ered to as“bedding fractures ”-locating in marine clay beds in parallel with bedding plane. The bedding fractures in hilly lands as well as in basin are recorded.
The Osaka Group, which widely distributes in the Osaka Basin and surrounding hilly lands, is characterized by the alternations of marine clay and non-marine sand and gravel bed. The bedding fractures, therefore, were supposed to have been formed in marine clay bed owing to its brittle properties, near faults and flexure in the Osaka Group. The fractures are observed always with a fault or a flexure, but converses are not generally true. Many slope failures, which had filed with cutting hill side, almost happened along bedding fractures. This paper also presents the studies on the behaviours of the fractures associated with several construction works and on the mechanical properties of the fractured material.

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The characteristic natures of unsaturated flow in fractured rock covered with surface soil was studied by means of 3 methods: (1) field measurement of discharge rate and electric conductivity changes of ground water flowing mainly through the unsaturated zone, (2) tracer test in the field and (3) experiment by the use of idealized model of fractured rock.
The experimental model is characterized by coexistence of two types of fracture system: micro fissure subsystem and macro fissure subsystem.
The obtained results are as follows.
(1) Electric conductivity of the infiltrated ground water decreases soon after starting of rain, and on the basis of this result, it can be thought that some part of rain infiltrate rapidly through the unsaturated zone.
(2) However, tracer (salt water) put into surface soil before rain did not find in the infiltrated ground water over the long observed period.
(3) This difference in responce to rain fall is, mainly due to the existence of“Seepage Path” in the unsaturated zone.
(4) It has been made clear by the experiment that the seepage path is generally created in the unsaturated zone.

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To evaluate the deterioration characteristics of soft rocks, several convenient tests, which need not to pay paticular attentions to preserve the raw samples, are selected and practiced to Tertiary mudstones mainly. After examining the correlations between those test results, actual earthpressure behaviours are compared with the testing results.
In conclusion, following 6 items, which are thought showing the expansive potential of clay minerals in soft rocks, are selected. Those are montmorillonite content, clay content, contents of silt and clay particles, plasticity index, water absorbing amount and failure property of samples set in the water.

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