ENGINEERING GEOLOGY
Year:2019 | Volume:12 | Issue:3|Papers Count:6

Determining the mechanical and dynamic parameters of the rocks under different environmental conditions of laboratory, device, and rock samples tested. Triaxial test is one of the most useful tests for mechanical behavior of rocks, which be done by advanced servo-controlled devices, can determined important parameters such as mechanical strength, modulus of deformeabilities and variations in the velocity of the wave during loading continuously. In this paper, at first some of the physical and geological characteristics of two types of clastic rocks (sandstone and tuff) evaluated, and then their mechanical and dynamic parameters determined during servo-controlled triaxial test in different conditions of lateral and axial stress studied. The values of parameters such as modulus of deformeability, the poisson's ratio, and longitudinal and transverse wave velocities, which are usually stated constant, change with increasing axial and lateral stresses during the test, because the sample's behavior changes from elastic to plastic during test. Therefore, providing fixed value for a parameter can't be logical and must specify the conditions for its determination along with the declared number. The results of triaxial test of this study, carried out by the ISRM standard method, show that the resistance values, the modulus of deformeability, the poisson's ratio and the wave velocity of the longitudinal and transverse waves for the sandstone sample are higher than that of the pyroclastic sample, due to the difference in physical properties and the structure and texture of these two rocks. The range of variations of these parameters is different in two specimens.

Brittleness is an important problem in rock boring. So far, various methods have been introduced for determining rock brittleness but no method has yet been standard to measure it. In this paper, an empirical study was done to provide a reliable method for predicting the S20 brittleness index. The S20 brittleness test was done for 35 limestone blocks pick out from different parts of Iran in dry and saturated state. In addition, physical (dry density, porosity, electrical resistivity, Schmidt rebound hardness number and water absorption), mechanical (uniaxial comprehensive strength and point load index) and dynamical properties (P and S wave velocity) was measured. Finally, the classification of the samples was done based on the studying of petrography and mineralogy and statistical studies were done for each class. According to the results, predicting S20 based on the provided classification has a high degree of certainty. In addition, by studying the brittleness of the samples in dry and saturated state, it was determined that the presence of Montmorillonite clay mineral causes a decrease of brittleness and the presence of intergranular micro cracks and high porosity leads to an increase brittleness in the saturation state relative to dry state.

Rock is a brittle naturally that is sobjected to a variety of environment impacts, such as temperature, confining pressure, humidity and water erosion. Moreover, the effect of temperature on rock fracture in most engineering fields has been considered. These include the determination of the resistance of rock structures to accumulate atomic waste in underground reservoirs, the hydraulic fracture process for extraction of oil and gas from different layers of the earth and analysis of the structures of underground mines. In this paper, we investigate the effect of temperature on mode I and mode II fracture toughness of Lowshan sandstone. To investigate the effect of temperature on mode I and II fracture toughness, was used a Cracked Chevron Notched Brazilian Disc. In this study, the specimens were subjected to a temperature of 20, 60, 100 and 150℃ . The results show that, with increasing temperature up to 150℃ , mode I and II fracture toughness of sandstone increases.

Soil particle arrangement affects soil behavior. Determining the arrangement of soil particles is complex. In this paper, wavelet transformation based on digital image processing was developed to determine the soil particles arrangement. Soil image is decomposed to 512×512 pixels small zones and is analyzed by wavelet transformation. For each analysis zone, an energy index is calculated. Since the energy can be calculated discretely for horizontal, vertical and diagonal directions, more data about the soil particles arrangement such as particles shape, particles orientation, and fabric can be acquired. For this purpose, the energy index is determined by comparing horizontal and vertical energies. Imaging of soils is done by sediment imaging test and flat surface test, and the energy index is calculated and compared for both methods. Energy index values greater than zero indicate that the particles are horizontally arranged, while the energy index values below zero represent the vertical arrangement of the particles. Therefore, the energy index is an appropriate indicator for determining the soil particle arrangement. Determination of particles arrangement by the DIP method reduces the operator and decreases errors.

Joints, deformation bands and faults are physical structures in rocks that have been developed as tabular zones of strain and fracture in response to tectonic and gravitational loading. The flow properties of faults are in general quite complex, because they can act as conduits or barriers to fluid flow. In most cases, a fault displays both aspects of this complex signature in time and space. Thus, the accurate description of permeability in the fault zone is an important aspect of the overall characterization of the reservoir or aquifer. Fault zone components consist of sheared joints, deformation bands, fragmented rock, fault rock, and slip surfaces, while damage outside of the core is in the form of joints, sheared joints and deformation bands. The distribution and orientation of these components may be variable within a fault zone, and each component has its hydraulic properties that vary as functions of geologic, mechanical, and hydrologic condition. Further, the infl uence of a given structural component on fl uid fl ow within and around a fault zone depends strongly on the component’ s geometric relationship to other structural components and to the direction of fl uid fl ow in this research the different models that describe the hydraulic behavior of faults has been reviewed.

In many plains in Iran, including those in Dasht-e-Neyshabur in Northeast of Iran, the dangerous phenomenon of subsidence has occurred. The main source of water supply in this plain is groundwater resources. Due to over-exploitation of groundwater resources, land subsidence has occurred and tension Fissures and splits have appeared on the surface in different parts of this plain. The main purpose of this research is to analyze the distribution and mechanism of Fissures formation caused by land subsidence. Using Sentinel 1 satellite sensor data, the land subsidence range in this plain was investigated, and using Quick Board and Sentinel 2 sensor data which have high spatial resolution, the Fissures in subsidence zone were determined. Then, during field observations, the existence and position of these Fissures were verified and, using GPS, full coordinates of the Fissures including 25. 5 km of continuous and discontinuous Fissure and 181 Fissures were mapped and a map from the plain’ s Fissures was drawn. In addition, the possible and covered Fissures in different areas of the plain were studied and identified in the maps. Geo-electric data from the plain and the condition of bedrocks were analyzed based on conceptual models of Fissure formation. Based on the investigations and taking into account the geometric shape and condition of the plain and its subsurface, it can be said that: the mechanism of the mechanical-based model, the mechanism of aquifer materials’ heterogeneity as well as tension stretch mechanism, are the most important mechanisms in the Fissure formation in Dasht-e-Neyshabur.