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7. During an excavation for a tunnel, 250 m below ground level, a highly fractured siltstone rock mass with two major joint sets and many random fractures is encountered. The RQD from the rock cores is 40% and the average UCS is 70 MPa. The joints with average spacing of 75 mm are rather continuous with high persistence with apertures of 3-5 mm, and they are filled with silty clay. The joint surface walls are highly weathered, undulat- ing, and slickensided. There is some water inflow into the tunnel estimated as 15 L/min per 10 m of tunnel length, with some outwash of joint fillings. Estimate RMR, Q and GSI. Assume a unit weight of 28 kN/m³ for the rock mass

7. During an excavation for a tunnel, 250 m below ground level, a highly fractured siltstone rock mass with two major joint sets and many random fractures is encountered. The RQD from the rock cores is 40% and the average UCS is 70 MPa. The joints with average spacing of 75 mm are rather continuous with high persistence with apertures of 3-5 mm, and they are filled with silty clay. The joint surface walls are highly weathered, undulat- ing, and slickensided. There is some water inflow into the tunnel estimated as 15 L/min per 10 m of tunnel length, with some outwash of joint fillings. Estimate RMR, Q and GSI. Assume a unit weight of 28 kN/m³ for the rock mass

Applications and Investigations in Earth Science (9th Edition)
Applications and Investigations in Earth Science (9th Edition)
9th Edition
ISBN:9780134746241
Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
Chapter1: The Study Of Minerals
Section: Chapter Questions
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7. During an excavation for a tunnel, 250 m below ground level, a highly fractured siltstone rock mass with two major joint sets and many random fractures is encountered. The RQD from the rock cores is 40% and the average UCS is 70 MPa. The joints with average spacing of 75 mm are rather continuous with high persistence with apertures of 3-5 mm, and they are filled with silty clay. The joint surface walls are highly weathered, undulat- ing, and slickensided. There is some water inflow into the tunnel estimated as 15 L/min per 10 m of tunnel length, with some outwash of joint fillings. Estimate RMR, Q and GSI. Assume a unit weight of 28 kN/m³ for the rock mass
Transcribed Image Text:7. During an excavation for a tunnel, 250 m below ground level, a highly fractured siltstone rock mass with two major joint sets and many random fractures is encountered. The RQD from the rock cores is 40% and the average UCS is 70 MPa. The joints with average spacing of 75 mm are rather continuous with high persistence with apertures of 3-5 mm, and they are filled with silty clay. The joint surface walls are highly weathered, undulat- ing, and slickensided. There is some water inflow into the tunnel estimated as 15 L/min per 10 m of tunnel length, with some outwash of joint fillings. Estimate RMR, Q and GSI. Assume a unit weight of 28 kN/m³ for the rock mass
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