Rock fractures play a significant role in the mechanical behavior of fractured rock masses. Understanding the shear strength characteristics of rock fractures is crucial for a wide range of rock engineering applications. In the literature, many experimental studies have been presented to analyze the shear strength of rock fractures. The strength of rock fractures is significantly dependent on fracture geometry that can be altered during the historical shearing process. This study presents a brief analysis of repeated direct shear of mated rock fractured. We conducted five repeated shear test simulations under constant normal load conditions using a predictive shear model presented in our previous work. The fracture surface used in the first round of shear simulation is scanned from a natural granite fracture surface. After shearing, the fracture surfaces are repeatedly used for the next rounds of shear simulations. The results generally show that the repeated shear induces irreversible surface degradation, which reduces the shear strength and normal displacement. The findings of this study provide valuable insights into the shear strength behavior of rock fractures, which can be utilized to enhance the accuracy of numerical models for analyzing the mechanical behavior of fractured rock masses and to provide practical implications for the design and stability assessment of rock structures in various rock engineering projects.

Characterizing rock mass discontinuities is a crucial aspect of rock engineering. Current automatic methods for discontinuity identification from 3D point clouds generally do not provide mathematical descriptions of individual 'joints'. To overcome this limitation, this article proposes a three-stage approach with the following steps: (i) identification of 'dis-continuity sets' or 'families'; (ii) identification of 'clusters', defined as continuous sets of nearby points that belong to a given discontinuity; and (iii) identification of 'individual joints,' defined as one or more 'clusters' whose spatial position suggests that they conform to a single discontinuity, even without fulfilling a continuity condition. The process con-cludes with a mathematical representation of joints using convex hulls, which can be em-ployed to characterize the rock mass. The proposed approach is validated using synthetic and real cases. Results illustrate that the developed tools can efficiently identify convex hulls that represent individual rock discontinuities from 3D point clouds.

An excavation wall is commonly constructed as a support structure to give support vulnerable slopes of soil and rock ground, particularly in hilly regions. Many studies are available on excavation walls in soil, but a few investigations have been done on excavation walls in rock. Also, those studies often overlook cohesion between rock joints. This study addresses this gap by developing a two-dimensional physical model of a flexible excavation wall supporting a footing on an artificial rock mass with orthogonal joints and with slight staggering. The ap-parent cohesion value resulting from the staggered rock joints was analytically calculated using force equilibrium analysis. Afterward, a distinct element model (DEM) was created using the universal distinct element code (UDEC) to compare experimental observations. The out-come of the analysis shows the experimental values align more closely with numerical values when apparent cohesion is considered in the numerical model.

The Gordon Underground Power Station in Tasmania is part of the Gordon-Pedder Hydro-Electric Scheme owned and managed by Hydro Tasmania. Completed in 1978, the station's 96m length, 22m width, and 31m height cavern reaches a depth of 183m below ground beneath Lake Gordon. The Gordon cavern was designed with a traditional arched roof profile. At the time of construction, Lack, Bowling, and Knoop (1975) published detailed studies that documented the in-situ rock strength, stress regime, and deformation modulus that provides a record for us today. The cavern support consists of grouted rock bolts, steel mesh, and approximately 150mm sprayed shotcrete. The rock bolts used are slot and wedge type with copper grouting tubes. These bolts were adopted by the Hydro-Electric Commission of Tasmania and the Snowy Mountains Hydro-Electric Authority for many of their projects at the time. Recent inspections across Hydro Tasmania's portfolio (Sainsbury et al, 2002) revealed that many of these slot and wedge bolts are ungrouted and have some level of corrosion. The cavern roof is covered with an average thickness of approximately 150mm shotcrete. While still functional, the shotcrete has deteriorated over time and requires ongoing inspection. To assess the current stability of the Gordon Power Station a detailed three-dimensional discrete element model (3DEC) has been developed. The model accurately matches the as-built excavation sequence and monitoring data from the time of construction until the present time. The model provides a basis to consider the potential long-term ground support degradation on the overall cavern stability.

The Well-being of Future Generations (Wales) Act 2015, based on the United Nations Sustainable Development Goals, is key to decision-making at the Welsh Government, and particularly in relation to transportation. One of the key outcomes of this act has been the Wales Road Review, stating that building new highways must end, with a shift to investing in public transport and active travel networks. Management and maintenance of existing strategic transportation links therefore becomes more critical. With this in mind, existing highways will still receive funding to ensure their continued operation, and will need to, in many cases, continue to operate past the ‘normal operation’ phase of their service life. This paper presents a case study of an engineering scheme developed to provide major maintenance and renewal for six rock cuttings forming the A477 trunk road, a critical transport link between Ireland (via the Pembroke Dock) and the United Kingdom through west Wales. The aim of the project was to assess the condition of the rock mass and the rock slope stabilisation systems that have been in place for nearly forty years. The stabilisation measures (tensioned rock anchors, rock dowels, shotcrete and rock netting systems) were considered by the asset owner to be entering their ‘end of life’ phase. During the ‘end of life’ phase, the risk posed by rock fall hazards can increase significantly, and failure rates of the systems begin to show a marked increase. The cuttings were assessed by combining remote sensing methods with detailed inspections undertaken by rope access trained Engineering Geologists. Close liaison between all stakeholders throughout the project was key to successful delivery and was especially important during the early phases. The design was developed using the latest industry guidance on inspecting and maintaining grouted anchors. An observational approach to the testing and renewal of the tensioned anchors, and renewal of the other aspects of the rock slopes and stabilisation systems was integral to the design. Working safely above the A477 was an important consideration throughout, as the highway had to remain open to traffic and not be subjected to any significant disruption. An inspection and maintenance strategy was developed for the cuttings with the aim of providing a best practice example to be used for other highway rock cuttings throughout Wales. This paper highlights the need for a collaborative and observational approach to extending the ‘normal operation’ phase of aging highways rock slopes.

The Joint Roughness Coefficient (JRC) is an important parameter used to quantify the roughness of rock joints which significantly influences their shear behavior. Traditionally, two methods are used for estimating JRC. The first method relies on optical observation utilizing the Barton-Choubey suggested table. After obtaining the rock-joint profile using a profilometer, a comparison with the ten standard joint profiles in the Barton-Choubey table follows. This method exhibits a high degree of subjectivity. The second method involves a series of demanding laboratory tests, which are time-consuming and costly. In recent years, a third approach has been introduced, based on empirical equations that are functions of one statistical parameter. Whereas the scientific community has suggested a wide range of parameters, this paper uses Myers’ statistical parameter Z₂, which is the root mean square of the first derivative of the rock-joint profile and is considered highly reliable. After digitizing the rock-joint profiles obtained from different directions on a rock-joint surface, the estimation of Z₂ for each profile succeeds. Next, the parameter Z₂ applies to the empirical equations, and the JRC value is derived. Then the results are compared to those of the two usual methods. The JRC_s index value of the entire discontinuity surface is also studied instead of the JRC value in different directions. This concept is more realistic for the shear strength of rock joints study because the shear behavior of discontinuities in the field develops on rough surfaces of irregular morphology. This work concludes that a) the alternative JRC index calculation method simplifies the quantification process by requiring only digitized rock discontinuity profiles and, at the same time, limits subjectivity, and b) the JRC_s index of the rock-joint surface is an extension to the two dimensions of the JRC index of the rock-joint profile.