The deterioration of mechanical properties of rocks under cyclic dry and wet conditions was examined with evaluating the pore volume and pore size distribution changes by means of the mercury penetration method. The results are summarized as follows: At the initial stage during cyclic dry and wet condition, pore volume increases by microcrack initiation and potential crack propagation. The increase of this pore volume results from an increase of the weak planes, leading to the weakening the inherent rock strength. The slaking phenomenon is closely related to the propagation of cracks.
The purpose of this study is to develop new methods for soil type classification, mainly grain size distribution, using AE (Acoustic Emission) sensor and accelerometor under the invisible condition. These methods utilize the sound and the vibration phenomena which is generated while penetrating a cone into a soil or while shaving a bit on a ground surface. The penetration cone is provided with an AE sensor and an accelerometor for measuring sound and vibration of cone and with a load cell for measuring penetration resistance. Laboratory experiments have been performed on several kinds of soil which have different grain size distributions. The results of the laboratory experiments indicate that both the mean value of the AE signal and the acceleration increase with the increase in the penetration resistance and in the 30% grain diameter D30. The sliding contact type soil classification device, which is equipped with AE sensor, is also experimented. The results of the primary experiments show that the different AE power spectrum appear with variation of soil grain sizes and the AE power spectrum is not depended upon a sliding speed or a load. The penetration cone method is applied to a subway tunnelling works by a earth pressure balance type shield machine to investigate its usefulness for soil classification in the invisible chamber. The results of the field tests are agree with the data of laboratory experiment.
Sumba Island is situated at about 1, 500km ESE of Jakarta and is mainly composed of Neogene Tertiary and Quaternary marine sedimentary rocks. These consist of limestone, tuff and sandstone. Volcanic and intrusive rocks of the pre-Quaternary are also distributed. Most formations of marine sedimentary rocks are related to limestone and the major facies of limestone are coral reef origin. The topographical characteristics of marine sedimentary rocks areas on the island are coastal terraces and karst. Several steps of coastal terraces and cliffs developed along the seashore. Karst features such as dolines, sinkholes and caves occur in the limestone areas. Many springs exist in these areas, especially in the Kaliangga formation area, the Waikabubak formation area and the Kananggar formation area. The total number of small spring (5>Q≥1l/s) +moderate spring (100>Q≥5l/s) +big spring (Q≥100l/s) on the island is at least 124. Out of 124, 43 are moderate springs and 9 are big springs. One of the famous big springs is Waikelosawa where the quantity of flowing water is more than 1000l/s even during the dry season. Eighty percent (99 springs) of 124 springs exist below 500 m altitude. Most groundwater is spring water, but underground river also occur, for instance the Pabinjal-ai in thePraipaha Basin. Confined groundwater, however, occurs in the Anakalang Basin. In this area, aquifers are composed of limestone rich facies and aquicluds of tuff rich facies. These facies are of the Waikabubak formation. Columner sections of the existing tube wells show that the aquifers are of limestone, marl, sand and gravel. But, judging from the field data, the greatest proportion of groundwater consists of cavern and fissure water, most of them being unconfined karst spring.
A strong earthquake measuring a magnitude of 7.8 on the Richter scale shook areas of Kushiro in Hokkaido at January 15, 1993. The epicenter was located at 17km off Kushiro city, and the focal depth was about 107km. The Taiheiyo Coal Mine is located at the east end of Kushiro city. At the very moment of earthquake occurred, about 450 over coal miners worked in a variety of the deep pits about 600m below the seabed. To clarify the seismic intensity in deep underground space, a questionnaire seismic intensity survey was carried out to 31 Taiheiyo coal miners.Although Japan Meteorological Agency reported the maximum ground intensity of 6 at Kushiro areas, the obtained average seismic intensity in a underground of 600m was 3.1.