Geotechnical investigation of Chitral Slates, Hindu Kush Ranges, Northern Pakistan: case study
Keywords:
Geotechnical investigation; Hydrological study; Chitral Slates; Hindu KushAbstract
The present study was undertaken to find out different geotechnical properties of Chitral slates for heavy construction such as dam components like a weir, diversion and intake, sand trap, headrace tunnel, access tunnel and tailrace. The work has helped to analyze the behavior of these rocks during construction and under the imposed loading of any proposed structure. The highly deformed Jurassic Chitral slates are exposed along a large anticline in the Hindu Kush ranges situated in district Chitral, Northern Pakistan. A total of six bore holes were drilled, approximately at a distance of 1 km for each sample, for a detailed study of core samples and internal condition of boreholes. These include water pressure test, water table, Standard Penetration Test (SPT)/Cone Penetration Test (CPT), joints and fractures, and lithology. The studied core samples are highly jointed; average five joints per meter are present, which are in filled by clay and iron oxide. As a result of these joints, the water loss is very high. Water pressure tests were carried out at a specific depth in boreholes in uncased section. The picker test results were 26.75, 22.95 and 15.90 in Geo-11A and Geo-15 respectively. Many of the tests were not successful because of the jointed strata where the water pressure did not exceed the required pressure. The SPT failed in overburden due to the presence of heavy particles like boulder etc. The boreholes collapsed at various depths where they were grouted with cement to prevent them from collapsing. The borehole logs were prepared for each borehole along with detailed information
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