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Shotcrete is a key initial rock support component used in underground mining and civil projects. The strength of shotcrete plays a vital role in providing and deciding the support adequacy. The strength of shotcrete is evaluated by its uniaxial compressive strength (UCS) test that is usually conducted on extracted core samples. Shotcrete cores are commonly extracted from the test panels along the direction of its application; thus, its strength perpendicular to the direction of application is often neglected. The true bearing strength of shotcrete is thereby ignored despite the fact that higher stresses act normal to the direction of its application. Although the anisotropic behavior of shotcrete is well reported, no study has reported extensive testing of this scale and nature. This study reports extensive testing of shotcrete cores extracted from tunnels of a mega hydroelectric project in Pakistan. The study reports 7- and 28-days strength tests of shotcrete cores. The research also investigates the anisotropic behavior of steel fiber reinforced shotcrete and suggests that shotcrete exhibits higher strength perpendicular to the direction of its application.

Over the past few decades, numerous authors have published empirical correlations among rock mass classification systems, conducted under specific geological conditions. As a result, the validity of these correlations heavily relies on the knowledge of the original data. In this study, a comprehensive analysis was systematically carried out using field data obtained from various underground excavation sites, having a range of rock mass qualities, from very good to poor. The collected data were categorized into different classes based on rock mass conditions, providing a more specific analysis of correlation patterns. The RMR14has been correlated with several key parameters, including Q, Qc, lnQ, and GSI, within the context of underground excavation. Regression analysis was utilized to ascertain the correlation coefficients and assess the statistical significance of the relationships. The results revealed a greater regression coefficient when RMR14was correlated with ln Qand Qcfor the dataset representing very good class rock mass, indicating a stronger relationship within this specific category. When comparing the equations derived from the overall dataset, the correlation with Qcdemonstrated the highest Pearson's r value across all cases, indicating statistical reliability. The inclusion of rock strength using Qcmakes this correlation especially suitable for support selection in underground excavation.

Numerical modeling is a fine tool for the assessment of inaccessible zones or unforeseen conditions in geotechnical engineering. When modeling structures in rocks, the laboratory-determined properties must be factored as per rock mass classification. The joints present in rock mass can be utilized for assessment of wedges forming around the tunnels. Half tunnels or overhanging tunnels are constructed in steep rock slopes through slot cutting. This develops overhanging cliff in hard rocks that looked like a half tunnel. Half tunnels have advantage over conventional tunnels or open excavations as they require less excavation. The current construction practice of half tunnels is solely based on experience of construction in hard rock. This study discusses the stability of half tunnels and analyzes its design in the Himalayas. A road extension case study for existing 7-m span tunnel is modeled and studied. Finite element code is used to assess the stability of half tunnels by analyzing different possible scenarios. In addition, rock mass classification is performed along with wedge analysis, and analytical designs. It was found that massive rock mass is quite suitable for the construction of half tunnels. Also, most economical and stable half tunnel designs were recommended.

In Pakistan, most of the coal mines located in the Salt Range utilise wood or timber as the main component of support system comprising of cribs, two-piece and three-piece sets. The commonly used variety of timber by the coal mining industry of Pakistan includes Acacia nilotica(Linn.), delile and eucalyptus. This research work is focused on the strength characteristics of bending and compression members of acacia wood being used as support components in underground coal mines. Easy to use equations for the prediction of flexural strength, uniaxial compressive strength (UCS) of wood parallel and perpendicular to grain from density are also proposed. Efforts were made to enhance the bending strength of wooden beams of acacia which showed an increase of 23.45% through applying reinforcement. Moreover, full column crib strength was determined to evaluate its roof supporting capacity. Besides this an alternate compression member to acacia wood support has also been evaluated and introduced in the form of brick support.