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.

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Concept explainers

Methods to Determine Vertical Stress

The load applied to the soil is transferred to the underground. The presence of water at soil pores and solid grains above the soil are the primary components that are responsible for the effective load transfer. Due to the load acting, the internal component of the soil or the underground formations undergoes deformations or a tectonic shift. The amount of deformation depends upon the amount of load acting on the soil surface, which indeed, depends on the weight of everything present above the soil. Due to this, the underground soil element develops internal stresses which try to resist the tectonic changes.

Question

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.

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