Coastal protection structures are often constructed from locally quarried rock, and are subject to harsh service conditions throughout long service lives. Durability of the rock is essential. By means of a thorough review of engineering standards and similar documents we show that petrological properties are known to be key controls on durability, but seldom feature in design guides. We surmise this is due to the use of subjective petrographic assessments. A review of the wider geological literature shows that quantitative methods are commonplace in petrology, but have not been adopted in rock engineering. We report on recent research work from Iran which shows that durability can be accurately predicted by applying machine learning methods to customary rock mechanics properties, and we suggest that combining these approaches with quantitative petrological data will allow improved design of coastal protection structures.

Open-ended (OE) pile field tests performed in low density chalk have demonstrated a unique installation response not widely observed in other geomaterials. This has encouraged the development of new CPT based design methods (ICP-18). Recently, A campaign of small-scale pile and CPT tests on intact soft rock materials, has been undertaken using a new multi-axis loading frame offering new observations on this unique behaviour. Similarities in model and field scale numerical tests suggest that the effects of stress-state may be less marked in the case of structured materials. Although scaling and stiffness issues certainly exist, the performance of the ICP method is trialled at small-scale enabling a new discussion on the applicability of small-scale pile tests in rock, scaling aspects and the changes intact rock fabric under-goes during subject to pile insertion which are revealed using X-ray tomography.

Mechanized tunnelling is the most used construction method for long tunnels due to its high excavation speed and enhanced worker safety. For deep tunnels, the study of the interaction between the ground and the supports is essential for the structural design of both shield and segmental lining which may be subject to heavy loads. For such scenarios, it is crucial also to assess the risk of entrapment of the Tunnel Boring Machine (TBM). Despite the three-dimensional nature of the problem, full axial-symmetric or 3D numerical calculations are rarely employed in the design practice because are time-consuming and demand advanced numerical skills. A recent paper proposed a simple and effective numerical procedure based on full axial-symmetric analyses. The procedure is described and validated by comparing the results of a case study with reliable data reported in the literature, obtained through 3D advanced numerical approaches that explicitly simulate the radial gap closure.

The current paper deals with geotechnical challenges and tunnelling experience gained during the detailed design phase of new tunnels in the frame of the Sotra Link Project (SLP) in West Norway. It consists of several civil works between Bergen and Øygarden, along the existing Riksveg 555: 4 main road tunnels (Kolltveit, Straume, Knarrvika, Drotningsvik), 3 pedestrian and bicycle tunnels, 19 road and pedestrian underpasses, 23 tunnel portals, 22 bridges and viaducts, 14 kilometres of pedestrian and bicycle paths and 24 kilometres of two-lane access. Geotechnical complexities analysed in this work are mainly related to the design of technical solutions for rock support under the following conditions: i) low overburden with loose shallow deposits and interference with existing and new nearby structures, ii) metric fault zone extension with expected swelling potential. Starting from a preliminary solution based on the NGI Q-system, the detailed design overcomes these challenges throughout finite element numerical analyses. This approach leads to a suitable dimensioning of customized linings and specific tunnel face support, together with partial excavation phasing when required. Within this context, two significant case studies are discussed with reference to Drotningsvik main tunnels: the first one concerns the design of the sections close to Kiple Lake (Kiplevatnet), where partial front reinforcement and surface grouting are foreseen. The latter case deals with a fault zone crossing located 500 meters western, by adopting a full front reinforcement and partial excavation phasing. The observational method supported by an extensive monitoring campaign during the construction phase will allow for possible design optimisations based on properly back-analyses. Currently, the delivery tasks for Sotra Link project are in line with the contractual scheduling. The project contract was awarded in September 2021 for a total value of 1.25 billion € and the design phase is expected to finish in 2024, while the infrastructure will be opened to traffic in 2027.

Ornamental rocks are competent rocks that are usually arranged in layers of dozen meters of thickness. These form rock masses, affected by joints and fractures of tectonic origin and very extensive stratification planes. Thus, fractures and faults with extensions around hundred meters often cause important instabilities in mining operations. When blocks with tens of thousands of tons appear, their stability must be evaluated and, if it would be necessary, controlled. There are several known cases of plane failures involving large blocks of rock in limestone and marble quarries. Stability 2D analysis, such as the one developed by the limit equilibrium method of Hoek and Bray (1981), face certain difficulties. It makes sense, that block geometry is variable depending on the sections that we set, besides, this is just one of the differences considered among those chosen sections. In fact, a posteriori study of these instabilities would show, important lateral differences in the resistant conditions of the failure planes that drive to sliding. Moreover, the loading conditions induced, by blasting or by water inflows, are not equal in every single section. Taking advantage of the strength of these large potentially movable blocks, considered as a set of sections, it is possible to transfer the force requirements among them to compensate the lack of resistance of some specific sections with extra of the surrounding ones. So we provide, as an example, the back analysis of a large 40,000 t sliding marble block. Then we have divided a 40 m high and 60 m. wide block into 10 meters slices, to evaluate the whole equilibrium so we can explain the sequence of ruptures that led to its collapse.

Normally, two in situ methods are used to assess the rock at-rest earth pressure coefficient (k0): one is the Hydraulic fracturing method that obtains in-situ stress average over a sample of a few square meters, and the other one is the Overcoring techniques that measures in-situ stress average over grain size areas. This paper analyses a total of 17 hydraulic and 51 overcoring successful tests into the Sandstone rock. The parameter k0 has a big influence on the structures constructed into the rock. In this analysis is presented a secant pile wall with piles of diameter 0.75 m separated 1.8 m embedded into the Shale and Sandstone rock. At the beginning the movements predicted by 2D numerical model were ten times greater than the movements observed in the inclinometers during the excavation. Thus, in this study was found out that this large difference of the movement is due to the larger k0 coefficient. Next, the k0 coefficients were corrected so that the movements predicted by the numerical model match with those measured. The calibration of the k0 coefficient was up two times the empirical Jaky’s k0 coefficient. This calibration had influence reducing the resulting forces of the wall during the excavation phases. Finally, the k0 results from the in situ tests and the calibration values were compared, showing that both results concur for the k0 lower bound of the test results.