Based on the geological, engineering geological, structural–tectonical investigations and laboratory analyses, engineering geological model of the Croatian karst has been made. This model consists of three parts: shallow karst, transition zone and deep karst. Each one has its structural and tectonic characteristics.
Ogata, S. (Hokkaido University) | Kawasaki, S. (Hokkaido University) | Hiroyoshi, N. (Hokkaido University) | Tsunekawa, M. (Hokkaido University) | Kaneko, K. (Hokkaido University) | Terajima, R. (Kyokado Engineering Co. Ltd)
A series of fundamental laboratory tests was performed to develop a novel conceptual grout, that improves the sealability of soil and rock using microorganisms, hereafter denoted as biogrout. Biogrout, which includes calcium ions and glucose, is a material to produce the precipitation of calcium carbonate (CaCO3), which plugs voids of rock and soil and, moreover, cracks of rock. In our previous studies, precipitation tests on CaCO3), were carried out at 25°C. This paper especially focuses on evaluating the influence of the temperature on the precipitation of CaCO3), to consider applications of biogrout in soils of various areas with varying climates. In laboratory tests, biogrout was added to soils from vari-ous areas in Japan under wide-ranging temperatures (5 to 35°C), and the results showed that the tem-perature highly affected the precipitation of CaCO3), because of the temperature dependence of microbial metabolism.
High damage potential, relatively high pore pressures and limited pre-construction accessibility are the main features of subaqueous tunnels. Potential hazards include high water inflows or even a complete flooding of the tunnel in the case of a hydraulic connection to the seabed. In subaqueous tunnels high pore pressures may occur at small depths of cover, i.e. in combination with low effective stresses and low shear strengths of the ground, thus having a particularly adverse effect in terms of stability and potential deformations. The paper examines some of the geomechanical issues relating to subaqueous tunnels (face stability in fault zones, the limits of open mode TBM operation in weak sedimentary rocks and the effect of advance drainage in squeezing ground) by means of three case studies: the recently completed "Melen 7" Bosphorus tunnel, the soon-to-commence Lake Mead Intake No 3 tunnel construction and the future Gibraltar Strait tunnel project.
The longest pair of inclined shaft is located in the first pumped-storage power plant in Iran. The shafts are about 500 m long with inclination of 65° and with diameter of 6.2 m (center to center distances is 20.5 m). Several access galleries to save time were carried out and excavations in two phases (pilot and then enlargement). 12% of shafts lengths were excavated by blind shaft sinking. Mechanized method was utilized in 60% of pilot shaft (Dia.: 2.4 m), remaining part of shaft pilot was excavated by conventional drilling and blasting method (Dia.: 1.8 m). Enlargement of shafts were done by drilling and blasting method. Geological conditions at the pressure shafts are problematic due to presence of karst, weak rock zone and underground water leakage. This situation has caused some problems like redrilling of raise borer, reamer falling down, and several collapses in pilot and enlargement phase and at intersection of access gallery and shaft. Consolidation grouting, backfill concrete, fore poling and shotcrete by rebar used in order to solve mentioned problems. Pressure shafts excavation were carried out continually from Oct. 2005 to Feb. 2009 (40 months).
Importance of the detection of the low strength zones for the engineering geological and geotechnical modelling is stressed as well as illustrated with an example, and an appropriate method is described. The highest values of liquid limit and plasticity index in a geotechnical column regularly correspond to the lowest values of angle of internal friction. RNK method singles out one layer, often one of the weakest layers, as a reference, and uses relatively simple but numerous and very carefully performed tests to organize and compare data obtained in the area—allowing very useful extrapolations, and detection of all weak layers. Correlation of plasticity index and angle of internal friction is presented with several new series of very carefully obtained data. An instability in very fractured limestone is analysed in detail, which occurred during excavation at the shipyard near Rijeka in Croatia, because the low strength zone was undetected and its possible importance underestimated.
For the engineering design of underground structures in rock masses, knowledge of the natural in situ stress state is generally required–as basic information and as input to numerical programs supporting the design. This review paper covers the relevant key points, including the nature of in situ stress, the relation between structural geology and rock mechanics and engineering, rock stress measurement/estimation, the ISRM Suggested Methods for rock stress estimation, rock stress compilations, the influence of free surfaces on rock stress (including the Excavation Disturbed Zone and rock spalling), and other perturbations of the rock stress field, including a mention of the effect of natural voids in karst regions.
In order to investigate the influence of water vapor pressure of surrounding environment on fracture toughness of Mode I and II of rock, a series of semi-circular bend (SCB) test under circum-stance with various water vapor pressures were performed. The water vapor is most effective agent which promotes stress corrosion of rock. The rock used in the test was Kumamoto andesite, and the region of water vapor pressure was 10-2 to 103 Pa. It is made clear that elastic modulus and fracture toughness for both modes are dependent on water vapor pressure of surrounding environment and that these relations can be linear logarithmically.
The mathematical model is developed on the basis of the Discrete Elements Method for investigation of processes of gravitational flow of the granular materials. The problem about drawing of coal from high coals in sublevel caving systems is numerically investigated in two-dimensional statement. Influence of order of opening of discharge holes on drawing process is shown.
Filipponi, M. (Laboratoire de géologie de l’ingénieur et de l’environnement (GEOLEP), Swiss Federal Institute of Technology Lausanne (EPFL)) | Jeannin, P.-Y. (Swiss Institute of Speleology and Karstology (SISKA)) | Parriaux, A. (Laboratoire de géologie de l’ingénieur et de l’environnement (GEOLEP), Swiss Federal Institute of Technology Lausanne (EPFL))
Many recent tunnel constructions showed that uncertainties related to karst processes are a major issue. The main problem beyond these issues is the poor predictability of the location and characteristics of the karst structures. Research progress along the last two decades, on the understanding of the development of underground karst structures in time and space, confirmed that the development of karst conduits is not random but predictable. Essentially, it is now possible to quantify the probability of karst occurrences inside a karst massif by identifying the few inception horizons that guide the karstification in regional scale, reconstructing the hydrogeolgical history and winnowing different speleogenetical zones. We present a ground investigation method that consists in linking various existing evidences derived from geological and geomorphological data to a probability of karst occurrence. This allows assigning a risk to some specific 3D volumes of a karst massif.
A large number of the shotcrete slopes constructed during Japan’s post-war economic boom are now more than 30 years old, and their structural deterioration is an ongoing problem. There-fore, it is necessary to accurately assess the stability and durability of these existing slopes. In this paper, we propose a technique that converts data from seismic velocity and electric resistivity to porosity and saturation, and we used the proposed technique to evaluate weathering and groundwater fluctuation behind the slope. Evaluation data from boring samples indicates that the distribution of porosity and saturation of rock mass around the slope as calculated using the proposed conversion system are highly similar to those of the real rock mass conditions.