Discontinuity flow behaviour in fractured rock mass remains a challenge in rock mechanics. This is due to fluid path prediction and velocities through the unsaturated zone under changing moisture conditions. This study proposes using the rock engineering systems (RES) approach to examine the interaction of the principal parameters in assessing discontinuity flow behaviour in fractured rock. This is achieved by a soft approach 3×3 interaction matrix in which the leading diagonal of the matrix is partially saturated flow, discontinuities in the fractured rock mass and the application of infrared thermography and photogrammetry. A georeferenced photogrammetry model is employed for 3D geotechnical discontinuity feature extraction. The analysis of these interactions shows that partial saturation in fractured rock mass depends on the discreet fractures, fracture network connectivity and matrix influence on storage. The leading diagonals of this RES approach highlight the most critical parameters for partially saturated discontinuity flow behaviour in fractured rock.

Fluid flow shows different behaviors through rough fractures with different scales. Numerical study as a powerful tool can be used to simulate fluid flow through a fracture with different scales. Geometrical properties, such as physical aperture and roughness, are important factors that have to be measured precisely. Photogrammetry, as a high-precision technique, was hired to reconstruct three-dimensional (3D) model of a granite fracture with a dimension of 25 cm × 25 cm × 10 cm. A high number of markers and scale bars were used to scale and orient the 3D model of the fracture accurately. The obtained 3D model of the fracture was used to simulate fluid flow behavior in a rough rock fracture. To validate the numerical modeling, experimental hydraulic tests were conducted with different hydraulic gradients ranging from 20 (kPa/m) to 200 (kPa/m) with an interval of 20 (kPa/m) under 0.3 MPa normal stress condition. Then, the obtained 3D model was used to simulate fluid flow through the fracture in different side lengths of 5 cm, 10 cm, 15 cm, 20 cm and 25 cm with the same hydraulic gradients. The results showed that the relationship between the hydraulic gradient and the flow rate was nonlinear and followed the Forchheimer Equation. The obtained hydraulic apertures were normalized to the subsample size lengths and were compared together. The results show the normalized hydraulic aperture decreases by increasing the sample sizes.

The analysis of the stability of rock slopes requires studying both the rock mass and the discontinuities within it. Discontinuities are typically considered planar at a reduced scale of study, usually on the order of meters. Furthermore, they tend to occur in sets with similar orientations. The characterization of these sets decisively influences the stability of the rock slope, making their study a key component. Traditionally, manual methods (compass, clinometer, measuring tape, etc.) have been used to collect data on the rock mass. However, this data collection is subject to operator subjectivity, potential hazards from falls or rockfalls, or even weather conditions. In this regard, the use of remote sensing techniques such as terrestrial 3D laser scanning or digital photogrammetry with RPAS (Remotely Piloted Aircraft Systems) has acquired popularity and acceptance within the scientific community in the last decade. Terrestrial laser scanning (TLS) is highly accurate and has been extensively used to geometrically characterize slopes. However, this instrumentation has the limitation that measurements are taken at ground level. Some areas of the slope may not be observable from the ground, thus limiting the surface that can be scanned. The popularization and accessibility of RPAS have enabled their widespread use in digitizing rock slopes using Structure from Motion (SfM), allowing for the reconstruction of surfaces in areas that cannot be digitized with TLS. However, the accuracy of this technique is lower compared to TLS. This research proposes the digitization of slopes using RPAS and airborne 3D laser scanning, with a comparison to data acquired with TLS assuming that the TLS data is correct. The study involves obtaining families of discontinuities using both techniques, and the comparison will allow for a discussion on whether the achieved level of accuracy and resolution are sufficient for addressing the geometric study of the discontinuity families. Two case studies are presented in the province of Alicante, Spain, analyzing the discontinuities in subvertical Cretaceous marls and another outcrop of Alicante Miocene.

Discontinuities significantly impact the stability of a rock mass and its hydraulic conductivity. Therefore, mapping rock discontinuities is essential to study rock mass behavior. This study explores the use of videogrammetry for digitizing rock mass at the tunnel face and measurements of joint orientations. Utilizing a mobile device for video capture, the method is compared against traditional laser scanning and mobile photogrammetry. Videogrammetry allows rapid data collection with smartphones or action cameras, emphasizing low-cost and accessibility. Results indicate that videogrammetry with a smartphone pro-vides an acceptable level of 3D reconstruction, with 3 mm control distance error and 1 cm cloud-to-cloud distance compared to a reference high-resolution laser scan. Discontinuity orientations measured from the videogrammetric 3D model show reasonable errors of less than 2-6° on average compared to data measured from the reference laser scan. The study validates videogrammetry as a practical, efficient alternative for rock mass characteriza-tion in underground settings.