A large-scale two-dimensional test rig was constructed to test block models that were loaded upward in the middle by a concentrated load which simulates the uplift load of a rock anchor. The objective of the tests was to quantitatively demonstrate the arching effect formed in the blocks of the model under the load of a rock anchor. Block models with different patterns of joints were constructed in the rig frame. Horizontal stresses are applied to the blocks by hydraulic cylinders. An upward load is applied in the bottom of the blocks along the middle line. During the test, the full-field displacements of the blocks were monitored with digital image correlation (DIC). The arching effect in the block model was clearly displayed by the DIC images. It also demonstrated that the load-bearing capacity of a block model was higher than the weight force of the overlying blocks within the failure cone that is the calculation rule of the current design method. The load capacity increased with the applied horizontal stress. The shape of the failure cone in a block model was structurally dependent on the joint patten of the model. The test results of five block models with different joint pattern will be presented in the paper.

Despite the new technologies available to assess the stability of rocky slopes, empirical methods continue to be a fundamental part of the initial evaluation process, verification of computational models, and monitoring of construction processes on site. The objective of this article is to propose improvements to the empirical method Q-slope by presenting five graphs based on the original method proposed by the authors in 2015. The graphs will al-low for reducing the time of data collection in the field, optimizing the evaluation of in-trinsic parameters of the method, and enhancing the technical transfer of the procedure.

Numerous Underground Rock Engineering (URE) projects like subsurface road/railway tunnels and hydroelectric power projects are constructed in the Lesser and Sub Himalayas, India. From the geological point of view, the Lesser Himalayan and Siwalik sandstones have been found in these regions. The design of the nationally eminent URE structures in the Himalayan region requires data on the physicomechanical properties of the rock. Hence, a comprehensive study has been conducted to determine the physicomechanical behaviour of the Lesser Himalayan and Siwalik sandstones. This study includes physical characteristics such as dry density (ρd), bulk density (ρb), saturated density (ρsat), effective/apparent porosity (neff), and water content (w); mechanical characteristic, i.e., Unconfined Compressive Strength (UCS) with acoustic signatures. The correlation between the Lesser Himalayan and Siwalik sandstone's physicomechanical properties is established. The AE characterization of the Lesser Himalayan and Siwalik sandstones under uniaxial compression loading is linked to their mechanical characteristics.

A considerable amount of slope stability analysis has been observed in jointed rock masses in which the GSI (Geological Strength Index) estimated at the outcropping level is considered input data to define the rock mass strength. However, this procedure is unsuitable when the rock outcrop scale and the slope scale are significantly different (e.g. open-pit slopes), resulting in an overestimated rock mass strength. For this reason, and in the absence of criteria to modify the GSI based on the scale effects, in this research, a new GSI version is proposed, called GSI_e or “equivalent GSI”. To define an expression for obtaining the GSI_e in terms of the rock mass properties, comparative stability analyses were conducted in a series of hypothetical slopes using two approaches: the first considers the rock mass as a discontinuous medium of rock blocks separated by discontinuities; the second considers the rock mass as an equivalent continuous medium characterized by an equivalent GSI. For the adequate equivalent GSI value, evaluated in each analyzed slope, the safety factor and the failure surface are similar in both approaches. In conformity with the results, a GSI_e formulation in terms of the slope height, the spacing, the intact rock strength, the persistence, and the joint conditions has been proposed. Finally, the formulation was validated by applying it in some cases of mining slopes where the failure occurred.

Rock tunnels are used extensively to convey water for the purpose of generating power, and such tunnels represent the main cost elements in typical Norwegian hydropower developments. Under Norwegian hydropower tradition, the key cost-reducing measure is to keep most of the tunnel length unlined, limiting the length of steel liners. Essential to this concept is to ensure that the stress in the surrounding rock mass exceeds the water pressure inside the tunnel, to avoid hydraulic failure. Reliable estimates of rock stress are required for the safe design of unlined pressure tunnels, and a new rock stress testing method, the Rapid Step-Rate Test, has therefore been developed to enable efficient estimates of rock stress. Since its introduction in 2021 the test method has been adopted by several contractors and plant owners, and some insights from the first few years of RSRT-testing are given, together with recommendations on proper test execution.

The excavation of underground infrastructures in geological sequences containing sulphates may cause swelling, water weakening, creep and karst. All these phenomena have been observed in tunnels for decades, but related technical problems still remain. This is especially true for geologically complex domains as Alpine environments, where the mechanical behviour of sulphates needs to be evaluated in relation to the structural complexity of the fracture network and of the 3D geometries of the orogenic context. This study, that is developed in the framework of the SALT project, a multiscale and interdisciplinary investigation of sulphate salts in the Alpine region, proposes a description of the main features of outcropping sulphates in Western Alps, providing useful preliminary information to afford technical issues related to sulphates during the realization of infrastructures in the Alps.