Problem 4 It is proposed to construct an underground tunnel 500 m below the ground. The drilled cores have an RQD of 85% and the number of joint sets is estimated to be 2. The joints are rough, undulating and unweathered with minor surface staining. The average uniaxial compressive strength of the cores is 190 MN/m². The major principal stress acts horizontally and is twice the vertical stress. The unit weight of the rock is approximately 30 kN/m³. The excavation is relatively dry, with some dampness and negligible inflow. The excavation span is 10 m. Estimate the Q-value and estimate the support category based on the calculated Q value. If unsupported, give the maximum unsupported span; If rockbolts used, give the length of rockbolts.

Problem 4 It is proposed to construct an underground tunnel 500 m below the ground. The drilled cores have an RQD of 85% and the number of joint sets is estimated to be 2. The joints are rough, undulating and unweathered with minor surface staining. The average uniaxial compressive strength of the cores is 190 MN/m². The major principal stress acts horizontally and is twice the vertical stress. The unit weight of the rock is approximately 30 kN/m³. The excavation is relatively dry, with some dampness and negligible inflow. The excavation span is 10 m. Estimate the Q-value and estimate the support category based on the calculated Q value. If unsupported, give the maximum unsupported span; If rockbolts used, give the length of rockbolts.

Fundamentals of Geotechnical Engineering (MindTap Course List)

5th Edition

ISBN:9781305635180

Author:Braja M. Das, Nagaratnam Sivakugan

Publisher:Braja M. Das, Nagaratnam Sivakugan

Chapter10: Shear Strength Of Soil

Section: Chapter Questions

Problem 10.10P

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