Kalvatar,shakil (0443725)- ENGR 5317 Assignment3B

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Laurentian University *

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5317

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Mechanical Engineering

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Jan 9, 2024

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Student Name: - Soham Salakhana Student ID: - 0439767 Student Name: - Shakil Kalvatar Student ID:- 0443725 Subject name: Application of Rock Mechanics in Mine Design Subject Code: ENGR 5317 Assignment: - 3 A 5 m × 6 m mine access tunnel (with 1 m arched-back) is constructed at a depth of 1000 m. The rock density is 2700 kg/m3. The vertical in situ stress is induced by gravity and the horizontal stress perpendicular to the tunnel long axis is 1. 5 times of the vertical stress. The horizontal stress in the tunnel long axis direction is 1.3 times of the vertical stress. Only uniaxial compression tests of intact rock were conducted. The average uniaxial compressive strength of the rock is 200 MPa, and the average crack initiation stress determined from lab test is 84.2 MPa. The Young’s modulus and Poisson’s ratio of the intact rock are 50 GPa and 0.2, respectively. The mine access tunnels pass through rock mass zones that can be modeled using the generalized Hoek-Brown model. Very careful drill-and-blasting is conducted to minimize excavation-induced damage to the rock mass. 5 m Interpretation of above data in RS2 : A 5 m × 6 m mine access tunnel (with 1 m arched back)… The radius of curvature for the drift to input in the tunnel wizard is 3.5m (= 5 2 m + 1m)

Student Name: - Soham Salakhana Student ID: - 0439767 Student Name: - Shakil Kalvatar Student ID:- 0443725 Subject name: Application of Rock Mechanics in Mine Design Subject Code: ENGR 5317 We have taken Excavation boundary as a box with dimensions scaled by a factor of 4. ….As given the vertical in situ stress is induced by gravity and the horizontal stress perpendicular to the tunnel long axis is 1. 5 times of the vertical stress. The horizontal stress in the tunnel long axis direction is 1.3 times of the vertical stress… Vertical Stress ( 𝜎 3 ) = ?𝒆???∗??𝒄𝒌 ?𝒆????𝒚∗?.?? ??????? = 26.48 MPa Horizontal Stress ( 𝜎 1 ) = Vertical Stress* 1.5 = 39.72 MPa Tunnel Long Axis Stress ( 𝜎 z ) = Vertical Stress* 1.3 = 34.424 MPa … Also given that The average uniaxial compressive strength of the rock = 200 MPa The average crack initiation stress = 84.2 MPa So, Hoek Brown Parameter (mi) = 8 * ?𝑶?𝑲 𝑼?? ??𝒂𝒄𝒌 𝑰????𝒂???? ???𝒆?? mi = 19.0

Student Name: - Soham Salakhana Student ID: - 0439767 Student Name: - Shakil Kalvatar Student ID:- 0443725 Subject name: Application of Rock Mechanics in Mine Design Subject Code: ENGR 5317 Given that The Young’s modulus = 50 GPa Poisson’s ratio of =0.2 Model = Generalized Hoek Brown model. Note that the disturbance factor was taken as 0 since very careful drill-and-blasting was conducted

Student Name: - Soham Salakhana Student ID: - 0439767 Student Name: - Shakil Kalvatar Student ID:- 0443725 Subject name: Application of Rock Mechanics in Mine Design Subject Code: ENGR 5317 (a) For the unsupported tunnel, field observations using borehole and micro seismic data indicate that the maximum depth of failure on the tunnel roof is about 1.30 m. The maximum depth of failure on the sidewalls is about 1.25 m. Use RS2 (accessible from computers in F228, or remotely (contact IT for remote access info)) to analyse the excavation behaviours and back calculate the peak GSI value of the rock mass. The residual strength of the rock mass can be estimated from the GSI system with GSIr = 30. Solution: First, we have taken GSI values in increments of 10, descending from 70, to place an upper and lower bound on the GSI yielding the correct depths of failure. GSI was determined to be between 30 and 50 this way. Then, they were decremented from 50 in steps of 5, Rock mass GSI as equal to around 40. The screenshots below show the change in depth of failure to observe require depths of failure (1.25m for the walls and 1.3m for the Roof). GSI 50

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