The Kastamonu Castle located on a sandstone hill with Eocene age is one of the most historical and touristic places in Kastamonu city center. The settlement of the city was expanded towards the hill of Kastamonu Castle and was influenced by a numerous rockfalls occurred in the past. The rock-fall problems around the castle could be related to jointing, weathering, freezing-thawing and earthquake effects or combination of them. In this study, the rockfall problems of the western and southern part of the castle are evaluated by two-dimensional rockfall analyses along six different profiles due to the fact that these areas are in more critical situation because of closer residential areas. Different size of rock blocks and various types of movements are taken into consideration in the analyses. Fall-out distance, bounce height, kinetic energy and velocity of the rocks for sandstone unit are separately evaluated. The obtained data are used to define the possible rockfall hazard zones. Finally, the areas having potential rockfall risks are distinguished. Based on the evaluation of the data, removing of unstable blocks and supporting the area with the protective fences are suggested.
Construction projects are becoming more challenging and require as much instrumentation information as possible. Two new types of instruments have been developed by Solexperts to satisfy these needs. Both instruments have been field proven. The MagX extensometer is based on the magnetostrictive measurement principle. The displacement of 20 positions along a 15 m curved or straight measuring line can be simultaneously measured with high precision. The instrument is configured as a manual or automatic device. The Reverse Head Extensometer (RHX) continuously monitors the propagation of deformation during excavation providing important continuous time-relative information about excavation activities to control the excavation process, optimize design and site activities. It consists of up to 20 extensometer modules. The data logging head is located at the deepest point of the borehole instead of at the surface. This reverse configuration allows collection of continuous time-relative data as its modules are successively destroyed by the excavation.
Mode I fracture toughness (KIC) of three crystalline marbles with the same mineralogy but different grain size distributions are measured using both Cracked Chevron-Notched Brazilian Disc (CCNBD) and Hollow Centre Cracked Disc (HCCD) specimens. For each marble, KIC values obtained from both CCNBD and HCCD specimens are well fitted. Measured KIC values are negatively correlated with grain size while are correlated with measured P-wave velocity (Vp).
An unexpected and instantaneous slide of rock mass from escarpment of a side cut, and which had already been partly remedied, occurred on the road Jablanica—Prozor/Rama near Mary’s cave. The entire rock mass on the studied site is divided into individual blocks in the form of vertical columns and prisms. The main rock mass rests on primary fractures with a gradient of 30–80°, which corresponds to limit angles of friction in cracks with similar fills, so there is a danger of new slides. Geotechnical investigations, which consisted of geological engineering works and geotechnical analyses, were performed on the site. The aim of investigations was to establish engineering-geological characteristics of the examined slope, reasons of instability, and to propose rehabilitation measures on the analyzed location.
This paper presents the origin and the type of instability phenomena in the Rjecina and Sušacka draga valleys near the town Rijeka, Croatia. Both locations are part of unique morphostructural unit. Karstified carbonate rocks prevail in this area. Paleogene siliciclastic sedimentary rock complex, i.e. flysch, has a form of a squeezed syncline between carbonate rocks. Geological boundaries between carbonate and flysch rock mass are tectonic, but with different mechanism of origin. Erosion processes and gravitational forces have caused disintegration of the carbonate rock mass, separation of blocks and their sliding over the flysch bedrock, as well as the accumulation of talus on the toe of rocky scarps. During the time, coarse grained fragments originating from the rockfalls were mixed with soil-like material from flysch weathered zone. Disintegration of carbonate scarps, rockfall and talus displacements are a permanent phenomena. The comparisons of a recent instability show a distinction between Rjecina and Sušacka draga valleys.
Steeply dipping rockhead and cavities provide extreme challenges for design and construction of foundations in karst dolomite terrain. The Gautrain Rapid Rail Link will connect Johannesburg, Pretoria and the OR Tambo International Airport along approximately 80 km of align-ment with 10 railway stations. Approximately 15 km of the alignment is underlain by dolomite with nearly 6 km elevated on a viaduct. To facilitate detailed design and choice of foundation method for the viaducts founded in dolomitic bedrock or overlying residual soils the Bombela Civils Joint Venture opted to include single-hole reflection borehole radar surveys as part of the ground investigation works. First arrival time, signal attenuation and reflectors were assessed from radargrams to locate karst structures and geological discontinuities for distances up to 12 ms around each borehole. This paper describes procedures together with examples demonstrating the merit of borehole radar surveys combined with conventional ground investigation in karst dolomite.
The stability analysis of large-scale rock slopes in heterogeneous and discontinuous rock masses still presents one of the main problems in rock and mining engineering today. The case study of large-scale slope stability analysis in heterogeneous and discontinuous rock masses in the St. Juraj– St. Kajo open pit mine has been compiled. The geological formation of this site consists of flysch sediments which have layers with extremely different properties and unfavourable disposition in relation to slope configuration. This may result in forming the slip surface of composite shape. In order to obtain an appropriate solution for slope stability, limit equilibrium and numerical modelling methods of different computer programs have been used. The evaluation of physically acceptable solution is presented on the basis of calculation method and its obtained results for critical slip surface.<.p>
The world’s highest suspension bridge has been constructed across a 500 m deep canyon in karst at a remote location in Papua New Guinea to carry oil pipelines across the Hegigio River. The bridge has a main suspension cable and two wind cables, each cable requiring anchorage into cavernous limestone. For the south abutment located on a pre-existing cut and fill bench, an A-frame tower was erected on pad footings, but with the most critical issues surrounding an 11 storey temporary erection tower at the cliff edge. On the higher north abutment, the main cable required only a simple support structure, but the wind cable anchorages had to be constructed from a bench cut into the cliff face. Site investigation and work was particularly challenging, not only for the usual issues of karst but also because of the remote location and extreme topography, and for the control of risk during construction.
When describing exposures in the field or logging core in the laboratory of carbonate rock the logger would have to have at his or her disposal a small library of codes of practice and publications to be able to describe rock in terms of mineralogy, strength and discontinuities for geomechanics purposes.
At TUDelft logging of numerous boreholes were made in the very weak Cretaceous calcarenites for the proposed new tunnels of the main motorway through Maastricht the A2 (E24). B To allow for fast referencing, the classification descriptors were summarized on plasticized pocket cards becoming indispensable in the logging process. The mineralogical limestone cards are based on definitions for limestone and carbonate from a geology dictionary as well as including well-known tables compiled by engineering geologists in several publications. Additional cards were made and used to describe the geomechanical features also applicable to non-carbonate rocks.
Long-term application of Geomechanical classification (Bieniawski 1973) and Q-system (Barton et al. 1974) in Croatia has resulted in a database related predominantly to carbonate and clastic rock masses. On the basis of the classification of 461 geological situations during exploration works and tunnel construction, the relationship between classifications has been analyzed. For the purpose of deter-mining constants m and s at the Hoek-Brown failure criterion, the GSI and Q’ correlations for carbonate and clastic rock masses have been analyzed.