Effects of diagenesis on the geomechanical and petrophysical aspects of the Jurassic Bir El-Maghara and Masajid carbonates in Gebel El-Maghara,North Sinai,Egypt

Bulletin of Engineering Geology and the Environment - In the present study, the Jurassic Bir El-Maghara and Masajid Formations in North Sinai are subjected to a detailed microfacies analysis to...     

Hydrogeophysical study of the El Qaa Plain,Sinai, Egypt

The paper reports a study of the Quaternary aquifer in the El Qaa Plain using gravity, magnetic and geoelectric surveys. One hundred and twelve gravity and magnetic stations were measured and interpreted. The area is dissected by faults with orientations consistent with the Gulfs of Suez and Aqaba and the Nile valley. Groundwater data indicated an E–W flow and an increase in salinity toward the Gulf of Suez. The Piper diagram indicates that the water type of the El Qaa plain is Na–Ca–Cl–SO₄ and the hydraulic conductivity of the aquifer 50 m/day. The calculated effective porosity is about 43.1%.     

Microstructural, geochemical and geomechanical properties of caliche deposits from the Adana Basin, Turkey

The 1998 Ceyhan (Adana, Turkey) earthquake caused major damage to construction on caliche formations. Caliche (a heterogenous secondary calcium carbonate deposit formed in arid and semi-arid regions) is widespread in the Adana area. The paper distinguishes three types of caliche: massive, containing vegetation remains and containing gravel. The porosity, water absorption and unconfined compressive strength of these three groups of caliche were determined. The compressive strengths are low compared to caliches in other areas—an important consideration as Adana is the fourth largest city in Turkey.      

Effect of weathering on the geomechanical properties of the Miocene basalts in Malatya,Eastern Turkey

Miocene volcanic rocks are widely exposed in the eastern Taurids, Turkey. The geomechanical properties and weathering degree of the Middle–Upper Miocene basalts were determined at the Boztepe dam site in Malatya, eastern Turkey. An engineering geology map of the Boztepe dam site was made and the joint sets and the degree of weathering determined in the field. The degree of weathering and RQD values were obtained on some 1,195 m of core which was then compared with a series of geomechanical tests including unit weight, porosity, water absorption, uniaxial compressive strength and compressive wave velocity. The geomechanical properties were compared with the weathering classifications of ISRM (Rock characterization, testing and monitoring, p 211, 1981) and Kilic (Environ Eng Geosci 4:475–483, 1999)      

Mechanical and petrophysical properties of North Sea shales

One of the problems when evaluating potential borehole stability problems in the drilling of hydrocarbon exploration and production wells is the lack of relevant data to describe the lithologies. This relates in particular to the shales, since these constitute most of the overburden and are also the most troublesome. This paper presents a set of data from a variety of deeply cored shales from the North Sea. The shales have been extensively characterised and span a wide range of both petrophysical and mechanical properties, depending on, for example, burial history and diagenesis. Special characteristics of shales have been tested and described, including pore size distribution, permeability, anisotropy and temperature dependence. Appropriate procedures for sample handling, testing and interpretation have been developed or modified from other related sciences.     

Key geomechanical properties of the historically liquefiable TP-Lisbon sand

The intrinsic properties of sands have a strong influence on the behaviour of these soils. Therefore, particle shape and granular packing can provide relevant insights into the mechanical properties of granular geomaterials. This study presents the characterisation of the key mechanical geomechanical properties controlling the behaviour of an alluvial fine sand, which composes the liquefiable layer of the geological profile at ‘Praça do Comercio’ square, located in the downtown of Lisbon (Portugal). For this purpose, a comprehensive experimental plan was conducted in the laboratory using accurate testing procedures. The experimental plan addressed: (i) the evaluation of the particle shape from a large number of particles using a computational geometry algorithm and statistical procedures; (ii) the estimation of the minimum and maximum void ratio through two standard methods; (iii) the assessment of the stress–strain behaviour by triaxial tests using lubricated end platens and an embedded connection piston, and void ratio measurements using end-of-test soil freezing; and (iv) the stress-dependency assessment of seismic wave velocities using bender elements. Results are interpreted within the critical state soil mechanics framework, highlighting the effects of the particle shape and granular package on the behaviour of this natural sand. In addition, critical state and small-strain parameters are compared and thoroughly discussed against selected data of other sands. Results provide experimental evidence about the influence of the particle shape and granular packing on the key geomechanical properties of TP-Lisbon sand.     

Petrophysical and geomechanical properties of rocks from the oilfields of the Krishna-Godavari and Cauvery Basins, India

The petrophysical and mechanical properties of reservoir rocks from two major basins on the east coast of India were studied using samples cored from 19 wells in the Krishna-Godavari and Cauvery basins. Several of these drill holes are located in the producing oilfields in these basins. The purpose of the study was to investigate the relationships between the properties of the rocks including dry density, effective porosity, uniaxial compressive strength, tensile strength and Young's modulus. Their relationships are further elucidated using regression analyses. The results indicated that the petrophysical and geomechanical properties vary widely for the different sedimentary rocks and basement samples related to their depth and geological age. It is emphasized that the work should be further extended to assess its full potential in reservoir studies of the oilfields in these basins.     

Influence of loading and heating processes on elastic and geomechanical properties of eclogites and granulites

Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(V_p) and S-wave(V_s) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in V_p and V_s are estimated to be 1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson's ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.     

Petrophysical characterization and durability aspects of tufa rocks at Kurkur Oasis,Western Desert,Egypt

Bulletin of Engineering Geology and the Environment - Various kinds of rocks can be used as building stones based on their durability, appearance, and availability. During many periods of times,...     

Effects of freeze-thawing cycles on the physical and mechanical properties of basaltic and dolomitic rocks evaluated with a decay function model

Bulletin of Engineering Geology and the Environment - Basalts from Çorlu Karatepe and dolomite from Kırklareli subjected to freeze-thawing (F-T) cycles were studied, and the resulting...     

Effect of geomechanical properties on Cerchar Abrasivity Index (CAI) and its application to TBM tunnelling

Abrasiveness of rocks plays an important role in the wear of TBM tunnelling. Cerchar Abrasivity Index (CAI) test is the most commonly used method to estimate rock abrasiveness due to its simple, fast test procedure and economic benefits. This study investigated the correlation between CAI and geomechanical properties of igneous and metamorphic rocks. Single and multiple regression analysis were performed and predictive models for the CAI from geomechanical properties were developed. It is found that single parameter alone is not suitable to predict the value of CAI. The result of the multiple regression analysis shows that quartz content is less influencing factor to predict the value of CAI. Also, the correlation between CAI and NTNU’s Cutter Life Index (CLI) was examined and a predictive model for the CLI from CAI and geomechanical properties was suggested. Finally, the influence of CAI on disc cutter life prediction models was investigated and it was found that the variation of CAI has the maximum effect on the predicted disc cutter life in Gehring model.     

Estimating compressive and flexural strength of travertines with respect to laminae-orientation by geomechanical properties

Bulletin of Engineering Geology and the Environment - Travertine is an anisotropic rock considered as one of the most popular stone materials in the building industry. Due to its bedding and...     

Determining geomechanical parameters and a deformation uncertainty analysis of the Longtan Hydropower Station slope,China

Bulletin of Engineering Geology and the Environment - Accurately determining geomechanical parameters and rock mass deformation are key components of slope stability assessment as well as...     

Effects of loading-unloading and wetting-drying cycles on geomechanical behaviors of mudrocks in the Colombian Andes

The mudrocks in the Colombian Andes, particularly those exhibiting low cementation （bonding）, are susceptible to degradation when the environmental conditions change, which are challenging issues for engineering works. In this paper, the changes in physico-mechanical properties of mudrocks were moni- tored in laboratory, and some influential factors on the mechanical competence of geomaterials were studied. The geotechnical characteristics and experimental designs were developed from physical, chem- ical, mechanical and compositional points of view. In the tests, the techniques such as vapor equilibrium technique （VET） were employed to apply wetting-drying cycles and to control relative humidity （suction- controlled） and loading-unloading cycles through ultrasonic wave velocities technique. The results show that the main failure mechanisms for the laminated mudrocks start on the microscopic scale by fissures coalescence, exhibiting physico-chemical degradation as well; the global geomechanical behavior presents a state between a ductile, like rock, and a fragile, like soil. The obtained results can provide engineering values according to monitoring laboratory set, when compared with in situ conditions.     

Effects of loadinge-unloading and wettinge-drying cycles on geomechanical behaviors of mudrocks in the Colombian Andes

The mudrocks in the Colombian Andes,particularly those exhibiting low cementation(bonding),are susceptible to degradation when the environmental conditions change,which are challenging issues for engineering works.In this paper,the changes in physico-mechanical properties of mudrocks were monitored in laboratory,and some influential factors on the mechanical competence of geomaterials were studied.The geotechnical characteristics and experimental designs were developed from physical,chemical,mechanical and compositional points of view.In the tests,the techniques such as vapor equilibrium technique(VET)were employed to apply wettingedrying cycles and to control relative humidity(suctioncontrolled)and loadingeunloading cycles through ultrasonic wave velocities technique.The results show that the main failure mechanisms for the laminated mudrocks start on the microscopic scale by fissures coalescence,exhibiting physico-chemical degradation as well;the global geomechanical behavior presents a state between a ductile,like rock,and a fragile,like soil.The obtained results can provide engineering values according to monitoring laboratory set,when compared with in situ conditions.     

Application of RMR and Q geomechanical classification systems along the proposed Mujib Tunnel route, central Jordan

This paper highlights the engineering geological investigations that have been carried out along the proposed Mujib Tunnel. The geomechanical classifications – rock mass rating (RMR) and Q index for tunnelling purposes – have been used to categorize the rock mass along the proposed tunnel. This tunnel will be driven into the Cambrian Sandstones (Um Ishrin Sandstone Formation) which are characterized by two to three sets of structural discontinuities. The geotechnical information obtained from drilled boreholes as well as from surface discontinuity mapping using scanline techniques indicates fractured sandstone along the proposed tunnel. This would be classified as very poor to fair quality material using the Q indexand RMR values. An expert system was used to obtain the design parameters of the proposed tunnel and to determine the support requirements. Electronic Publication     

Influence of microfabric on geomechanical behaviour of tertiary finegrained sedimentary rocks from Central North Island,New Zealand

Tertiary to Early Quaternary fine-grained marine sedimentary rocks (soft rocks) of the Central North Island, New Zealand, suffer from high erosion rates and slope instability. In geomechanical laboratory tests they exhibit a range in behaviour which straddles the division between overconsolidated soils and rocks. Direct application of published classification systems to predict performance has been unsuccessful for New Zealand soft rocks so far. Mineralogical composition does not vary greatly between ages and locations, in contrast to geomechanical parameters. Most constituents are detrital, no cement has been precipitated and post-depositional diagenetic alterations are negligible. Mineralogy does not comprehensively account for the geomechanical performance of these rocks. More direct influence is exerted by their microfabric. Basic building blocks of the fabric are detrital grains, clay microaggregates, microfossils and larger clay aggregates. Grains, microaggregates and fossils are mechanically stable, but larger aggregates exhibit varying degrees of stability. The geometric arrangement of structural elements can be described within a framework of three fabric types, the skeletal, matrix and turbostratic microfabrics, which form an evolutionary sequence related to the loading history of the deposits. Some geomechanical characteristics of the rocks, particularly strength, cohesion and durability, correlate well with the fabric type classification. In all fabrics, contact between structural elements involve clay, and its physico-chemical properties are important for their performance under stress. The fabrics are dynamic and adjust to changing stress conditions by re-arranging their constituents and contact configurations. Their response to loading and slow unloading during regional uplift is quasielastic, resulting in a loss of stress memory. During rapid unloading by erosion or excavation stress relief fractures parallel to topography can develop. Aggregates and connector assemblages form weak links in the fabrics. They are less competent in their response to stress and wetting and drying than other structural elements. Their breakdown decreases effective grainsize, average pore size and permeability, and initiates further disintegration of the fabric.     

Impacts of impregnation chemicals on combustion properties of the laminated wood materials produced combination of beech and poplar veneers

The aim of this study was to investigate the effects of impregnation with boron compounds Borax (B_X), Boric acid (B_A), B_X + B_A, Imersol-Aqua (I_AQUA) and Timbercare-Aqua (T_AQUA) on combustion properties of the laminated wood materials produced combination of Oriental beech and poplar veneers bonded with Desmodur-VTKA (D_V) and Poly(vinyl acetate) (P_VAc) adhesives. The test samples, prepared from beech (Fagus orientalis Lipsky) and poplar (Populus nigra Lipsky) woods, were impregnated boron compounds by vacuum, I_AQUA by dipping and T_AQUA by brushing methods according to ASTM D 1413-76-99 and directions of the manufacturer. The laminated wood materials were prepared in the form of five layers, 4 mm thickness from the impregnated beech and poplar veneers according to TS EN 386. Combustion properties of samples after laminated and impregnated process were determined according to ASTM E 160-50. Considering the interaction of combustion type and impregnation materials, combustion temperature was found the highest in flame source combustion (F_SC) + T_AQUA (528.150 °C) but the lowest in without flame source combustion (WF_SC) + B_A (391.333 °C). Consequently, boron compounds and I_AQUA showed a decreasing impact on combustion properties of the laminated wood materials, produced combination of beech and poplar veneers, bonded with D_V. In consequence, impregnation with boron compounds and Imersol-Aqua of the laminated wood materials, bonded with Desmodur-VTKA, provides security for the usage of having high risk of fire.