Kalvatar,shakil (0443725)- ENGR 5317 Assignment3B

pdf

School

Laurentian University *

*We aren’t endorsed by this school

Course

5317

Subject

Mechanical Engineering

Date

Jan 9, 2024

Type

pdf

Pages

Uploaded by UltraGalaxyHippopotamus31

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

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

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

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 Strength factor represents the ratio of available rock mass strength to induced stress at a given point. There is a large zone of overstress surrounding the tunnel. All the rock within the contour marked 1 and the one which has a strength factor less than 1 and will fail if left unsupported . GSI 35

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

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 From the displacement contours, the overall maximum displacement (shown in status bar) is occurring in the floor of the tunnel. (b) Using the rock mass properties determined above, evaluate the influence of rock support on depth of failure. Fully grouted resin bolts (19 mm diameter, 220 kN load capacity, 2.4 m long, 1.2 m × 1.2 m pattern bolting) are used to support the tunnel roof and walls.

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 Compared against previous plastic analysis without support, we noticed that the influence of rock bolts on the maximum depth of failure decrease it from 1.25m to 0.650 m along the side wall and from 1.30m to 0.849 m along the roof.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

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 (c) If 100 mm thick shotcrete (E = 30 GPa, Poisson’s ratio 0.25, peak strength 35 MPa, residual strength 5 MPa, tensile strength 5 MPa) is added to the support system along with the rebars, evaluate the depths of failure (roof and walls). Solution:

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 Observation: It was observed After supporting tunnel we have noticed that the tensile support provided by the bolts would have been more evenly distributed, causing them to hold further reducing stress when used rebar with shotcrete.