Muhammad Junaid; Rini Asnida Abdullah; Radzuan Sa'ari; Wahid Ali; Amber Islam; Mahmut Sari
Abstract
This research work aims to critically analyze the efficacy of inexpensive and rapid 2D electrical resistivity tomography (2D ERT) survey for sub-surface geological delineation of granite deposits. The research work involves six ERT profiles using the Schlumberger protocol with an inner and outer electrode ...
Read More
This research work aims to critically analyze the efficacy of inexpensive and rapid 2D electrical resistivity tomography (2D ERT) survey for sub-surface geological delineation of granite deposits. The research work involves six ERT profiles using the Schlumberger protocol with an inner and outer electrode spacing of 5 m and 10 m, respectively. In addition, the unmanned aerial vehicle (UAV) survey is also performed to obtain the terrain information of the studied area. At the same time, a few boreholes are drilled to validate the 2D ERT interpretations. The 2D ERT survey reveals that strong resistivity contrast enables inverted resistivity imaging to characterize the deposit such as topsoil (100-800 Ωm), fracture granite (800-2300 Ωm), and solid granite (> 2300 Ωm). The results obtained from UAV, 2DERT, and borehole survey are further processed to estimate the bedrock to topsoil ratio to assess the feasibility of the deposit. The bedrock to topsoil ratio, estimated by 2D ERT and borehole, is 3.2 and 2.2, respectively. At the same time, the combined UAV, 2D ERT, and borehole survey calculates the bedrock volume 3.2 times to topsoil. Thus the research work allows us to conclude that 2D ERT is an inexpensive, viable, and efficient technique for sub-surface geological documentation, and helps select appropriate mining methods.
Hafeezur Rehman; Ahmad Shah; Mohd Hazizan bin Mohd Hashim; Naseer Muhammad Khan; Wahid Ali; Kausar Sultan Shah; Muhammad Junaid; Rafi Ullah; Muhammad Bilal Adeel
Abstract
The major factors affecting tunnel stability include the ground conditions, in-situ stresses, and project-related features. In this research work, critical strain, stress reduction factor (SRF), and capacity diagrams are used for tunnel stability analysis. For this purpose, eighteen tunnel sections are ...
Read More
The major factors affecting tunnel stability include the ground conditions, in-situ stresses, and project-related features. In this research work, critical strain, stress reduction factor (SRF), and capacity diagrams are used for tunnel stability analysis. For this purpose, eighteen tunnel sections are modelled using the FLAC2D software. The rock mass properties for the modelling are obtained using the RocLab software. The results obtained show that tunnel deformations in most cases are within the safety limit. Meanwhile, it is observed that the rock mass quality, tunnel size, and in-situ stresses contribute to the deformation. The resulting deformations also affect SRF. SRF depends on the in-situ stresses, rock mass quality, and excavation sequence. The capacity diagrams show that the liner experience stress-induced failures due to stress concentration at the tunnel corners. This study concludes that tunnel stability analysis must include an integrated approach that considers the rock quality, in-situ stress, excavation dimensions, and deformations.
Hafeezur Rehman; Wahid Ali; Kausar sultan Shah; Mohd Hazizan bin Mohd Hashim; Naseer Muhammad Khan; Muhammad Ali; Muhammad Kamran; Muhammad Junaid
Abstract
Support design is the main goal of the Q and rock mass rating (RMR) systems. An assessment of the Q and RMR system application in tunnelling involving high-stress ground conditions shows that the first system is more appropriate due to the stress reduction factor. Recently, these two systems have been ...
Read More
Support design is the main goal of the Q and rock mass rating (RMR) systems. An assessment of the Q and RMR system application in tunnelling involving high-stress ground conditions shows that the first system is more appropriate due to the stress reduction factor. Recently, these two systems have been empirically modified for designing the excavation support pattern in jointed and highly stressed rock-mass conditions. This research work aims to highlight the significance of the numerical modelling, and numerically evaluate the empirically suggested support design for tunnelling in such an environment. A typical horse-shoe-shaped headrace tunnel at the Bunji hydropower project site is selected for this work. The borehole coring data reveal that amphibolite and Iskere Gneiss are the main rock mass units along the tunnel route. An evaluation of the proposed support based on the modified empirical systems indicate that the modified systems suggest heavy support compared to the original empirical systems. The intact and mass rock properties of the rock units are used as the input for numerical modelling. From numerical modelling, the axial stresses on rock bolts, thrust bending moment of shotcrete, and rock load from modified RMR and Q-systems are compared with the previous studies. The results obtained indicate that the support system designed based on modified version of the empirical systems produce better results in terms of tunnel stability in high-stress fractured rock mass conditions.
