The study of the physical properties (geophysical methods) of rocks associated with its mechanical properties has recently received lots of attention. Recent studies show that geophysical methods especially the seismic and geoelectric methods are able to estimate the mechanical parameters and recognize their spatial variations, including anisotropy. Meanwhile, ELECTRICAL and seismic methods are the most used one.ELECTRICAL measurement is one of the non-invasive geophysical methods commonly used by engineers working in various fields such as mining, geotechnical, civil, underground engineering as well as oil and gas mineral explorations. This method can be applied both in laboratory and in the field. Numerous scientists have focused on the relation between RESISTIVITY and porosity. However, there is a very limited study on the relation between the ELECTRICAL RESISTIVITY and the rock properties apart from porosity.In this paper, changes in the ELECTRICAL conductivity of rocks during a uniaxial compression test were investigated in laboratory. The uniaxial compressive strength, elastic MODULUS, and density values of the samples were determined in laboratory. We installed special electrodes on seven nearly saturated core samples in order to measure the RESISTIVITY. Core samples had a 52-mm diameter and a 110-mm length. Two-electrode as well as four-electrode arrays were both used in RESISTIVITY monitoring in laboratory. Using a four-electrode array minimized the undesirable electrode polarization effects. In the four-electrode array, we used two non-polarizing Ag/AgCl electrodes mounted on the core sample. Our laboratory observations showed that there was not any electrode polarization effect. When we used a two-electrode array, the RESISTIVITY changes were less than 5 percent compared to a four-electrode array. In our laboratory investigation, we used different sedimentary core samples including sandstone, fossilioferous limestone and travertine. Maximum RESISTIVITY observed for the travertine core sample was less than 12 kohm. During the uniaxial compressive test, deformation measurements were made and the stress–strain curves were plotted. Tangent Young’s MODULUS values were obtained from stress–strain curves at a stress level equal to 50% of the ultimate uniaxial compressive strength.Sandstone core samples showed a RESISTIVITY increase in the whole strain range. On the contrary, the fossiliferous limestone samples (thin section showed that the sample was composed of tiny calcium fossils in a fine aggregate of micrite cementation) showed a RESISTIVITY decrease in the whole strain range. Travertine and limestone showed an intermediate behavior (RESISTIVITY increased in the lower strain and it decreased in the higher range). In other words, the onset of new crack formation occurs well inside the quasi-linear part of the stress-strain curve. The quasi-linear portion of the stress-strain curve was the result of a competition between closure of one population of cracks, and the growth of new propagation of the existing cracks.RESISTIVITY behavior during a uniaxial compression load is closely related to the pores in the lower strain ranges and then to the new induced fractures in higher strains. Our results showed that the ELECTRICAL RESISTIVITY may be a representative measure of the rock properties. Additionally, the effect of certain minerals on the rock’s RESISTIVITY must be taken into account. The results indicated that the rock structure had an important effect on the RESISTIVITY behavior during a mechanical loading.

ELECTRICAL RESISTIVITY techniques are well-established and applicable to a wide range of geophysical problems. 2D RESISTIVITY measurements can give information about both the lateral and vertical variations of the subsurface RESISTIVITY and can be used in a qualitative fashion for the identification of the structure and depth of masses. The RESISTIVITY inverse problem involves constructing an estimate of a subsurface RESISTIVITY distribution, which is consistent with the experimental data. This is a fully non-linear problem and its treatment involves iterative full matrix inversion algorithms, which can give good quality results. The back-projection RESISTIVITY technique (BPRT) can be applied to a set of apparent RESISTIVITY measures to quickly obtain an approximate image of the RESISTIVITY distribution of the investigated volume. This technique is based on the consideration that a RESISTIVITY perturbation in a point element (voxel) of a bounded region produces a change in voltage thus an apparent RESISTIVITY anomaly at the surface of the region, according to a sensitivity coefficient. The value of the coefficient is dependent on the position of the voxel considered in respect of both the current and the voltage dipoles, in agreement with the sensitivity theorem of Geselowitz. This consideration suggests that it is possible to correlate all the measured RESISTIVITY values, weighted by the appropriate sensitivity coefficients to each voxel of the investigated volume and to estimate the RESISTIVITY value of each cell of the model using a weighted summation of the apparent RESISTIVITY measurements. The BPRT considering a two-step approach. Initially, a damped least squares solution is obtained after a full matrix inversion of the linearized geoELECTRICAL problem. Furthermore, on the basis of the results, a subsequent filtering algorithm is applied to the Jacobian matrix, aiming at reducing smoothness, and the linearized damped least square inversion is repeated to get the final result. This fast imaging technique aims at increasing the RESISTIVITY contrasts, and practically, since it does not require a parameter set optimization, it can be used to easily obtain fast and preliminary results. The procedure proposed in this work consists of four steps: (1) Evaluation of sensitivity matrix B, (2) Inversion of matrix B using a damped LSQR solution, (3) Recalculation of a filtered Jacobian matrix B‘ obtained by means of a correlation filter, (4) Inversion of the filtered sensitivity matrix. The proposed technique is tested on RESISTIVITY synthetic data from the Schlumberger, Wenner, Dipole-dipole and Pole-pole arrays, the objective of which is to find the optimal parameter set. The synthetic tests carried out with 2D data suggested that a good compromise for 2D inversions is to choose 𝜆 for the Schlumberger, Wenner, Dipole-dipole and Pole-pole arrays, 0. 1, 20, 1 and 0. 5, respectively. Furthermore, all the synthetic tests carried out with 2D data suggested that a good compromise for 2D inversions is to choose 𝜒 ≈ 5. The approximate images using the BPRT inverse modeling for all synthetic data, with and without random noise, is compared with the least square inversion by RES2DINV software. Finally, a field case is discussed, and the comparison between the back-projection and inversion is shown.

The prediction of the mechanical characteristics of concrete according to its components’ properties has been of great interest. In the current study, attempts have been made to extract some experimental models to predict the MODULUS of ELASTICITY of high strength concrete based on some known characteristics of the concrete mix. To do so, 45 mix proportions including 5 different ratios of silica fume, i.e., SF/CM = 0, 5, 10, 15 and 20 percent, 3 water to cementations materials ratios, i.e., W/CM = 0.24, 0.3 and 0.4, and 3 types of coarse aggregates, i.e., limestone, quartzite and andesite were selected. 540 cylindrical specimens were cast, cured and tested after 7, 28 and 91 days. Regarding different ratios of silica fume and different ratios of W/CM, the relationship of MODULUS of ELASTICITY of coarse aggregate and concrete at different ages was discussed and some empirical equations were proposed. Special emphasis was paid on two proposed models, the comprehensive model and the simple model. The credibility of the models was verified using some independent experimental data.

Introduction: Restorative materials are under constant loadings from mastication hence, it is important to have the knowledge of structural properties of the restorative materials to have long-term success on restorations. Therefore, the aim is to compare the nanohardness and elastic MODULUS values of various restorative materials. Methods: Disc-shaped samples were prepared from a high viscosity glass ionomer-Equia Forte Fil (EFF), a compomer-Dyract (DXP), a hybrid ionomer-Geristore (GS), a giomer bulk-fill-Beautifil-Bulk (BB), two bulkfill composites-Venus Bulk-fill (VB) and Sonic Fill 2 (SF), and a nanohybrid composite-Z250. Samples of each of the tested materials (n=9) were examined under nanoindentation to evaluate ELASTICITY MODULUS (Er) and nanohardness (Hnano) scores. One of the samples had undergone through scanning electron microscopy (SEM) evaluation. Data were analyzed statistically using the Kruskal-Wallis test. Results: SF had the highest ELASTICITY MODULUS, followed by Z250 and DXP, without any statistical differences. However, GS had the lowest ELASTICITY MODULUS, followed by EFF (P<0. 001). Among nanohardness scores, there is no significant difference between VB, EFF, DXP, Z250, and BB groups. While SF showed the highest, GS had the lowest nanohardness scores. SEM images showed the differences between filler sizes and shapes. Conclusion: Main structural differences between glass ionomer-based and resin-based materials determined significant differences among related parameters of the restorative materials.

The purpose of this paper is to evaluation the dynamic parameters of soil including damping ratio, shear MODULUS, ELASTICITY MODULUS, and investigation of shear wave velocity in different sections, acquaintance with the methods of measuring each of these parameters and the effect of different conditions on these parameters. The research method is an overview of sources and references on soil dynamic parameters including damping ratio, shear MODULUS, MODULUS of ELASTICITY and shear wave velocity. According to the results of this study, soil structure has a direct effect on soil dynamic properties and with increasing shear wave velocity the bed soil becomes harder and quality of soil will be better. Almost all construction projects are built on soil, so correct recognition of soil and identification dynamic parameters behavior of soil can be effective to providing a safe and economical design. Among the dynamic properties of soil, shear MODULUS, damping ratio and MODULUS of ELASTICITY are more important and also there are various methods for measuring these parameters.

Vibration generated by vehicles during road transport has an important impact on agricultural products' damage process, particularly in the case of fruits and vegetables. MODULUS of ELASTICITY is one of the most conspicuous mechanical properties of fruits, the variation in which can be described as one of the most affecting damage criteria during transportation. This research was conducted to evaluate the effects of vibration parameters (frequency, acceleration and duration) as well as fruit position in the bin, on damage inflicted upon watermelon. Vibration frequency and acceleration were initially measured of different points of truck-bed to obtain the range of vibration frequency and acceleration distribution during transport. A laboratory vibrator was then employed to determine the factors influencing the damage incurred by watermelons during transportation. The damage was described as a difference of MODULUS of ELASTICITY of watermelon (flesh and hull) before and after the test. According to the results obtained from tests carried out on the truck-bed, vibration frequency mean values were 7.50 Hz and 13.0 Hz for 5-10 Hz and 10-15 Hz frequency intervals, respectively. Furthermore, vibration acceleration mean values were 0.30 g and 0.70 g for 0.25-0.50 g and 0.50-0.75 g intervals, respectively. Vibration frequency and acceleration mean values were used in vibration simulation. Vibration durations were 30 and 60 min and the damage was measured for watermelons positioned at top, middle and bottom in the bin. Laboratory studies indicated that, vibration frequency, vibration acceleration, vibration duration, as well as fruit position, which were taken into consideration as controlled variable parameters, significantly affected the extent of the damage. Damage incurred to watermelon flesh was higher than that to watermelon hull. Vibration with a frequency of 7.5 Hz, acceleration of 0.70 g, and duration of 60 min caused the highest damage. Fruits positioned at the top position in the bin incurred more damage than those in the middle and bottom positions.

Underground excavations provoke in their vicinity a region where the rock is disturbed, i.e., loosened due to micro as well as macro fractures. The shapes, dimensions, and properties of such so-called excavation damaged zones (EDZ) are of increasing importance for the planning and construction of geotechnical barriers in underground repositories for toxic and problematic wastes.Dynamic stability assessment of rocks after underground excavation is important. Mechanical changes related to an excavation damage zone (EDZs) leads to changes the physical properties of rocks. In fractured and unsaturated materials, RESISTIVITY is sensitive not only to the matrix ELECTRICAL properties but also to the saturation of the water phase and to the density and orientation of cracks. Recent studies show that ELECTRICAL RESISTIVITY tomography (ERT) and induced polarization (IP) methods are capable of monitoring the mechanical behaviour of EDZs.ERT and IP methods are performed in the galleries which are excavated in clay-rocks of the Tournemire test site located in the south of France. The aim of these geophysical investigations is the characterization of EDZ zones and hydro-mechanical behaviour. ERT is performed for an arc profile on the walls of the gallery, with 43 electrodes arranged on the floor and wall with a distance of 20 cm between them. Non-polarizing electrodes of Cu/CuSO4 were used. Interpretation of the ERT section on the straight line profile, carried out on the floor of the tunnel, confirmed the existence of a high ELECTRICAL RESISTIVITY zone near the surface (a fractured and partially saturated zone with a depth of 50 cm).A 2D ELECTRICAL RESISTIVITY model was developed to perform a tomography survey for the arc profiles on the walls of the underground excavations (horseshoe section). All the Wenner, dipole-dipole, and Schlumberger electrode arrays can be used for ERT surveying.Current and potential electrodes can be arranged on the floor, walls and ceiling of the tunnel, with equal intervals. A finite element method was performed in order to solve the Poisson equation for all points of the model space with respect to boundary conditions. The finite element approach involves solving a discretized form of the weak formulation of the Poison equation. For each quadripole (two current and two measured electrodes), the code is run once and the ELECTRICAL resistance can be calculated. The geometric factor of ELECTRICAL array can be calculated when the code is run for a homogeneous ELECTRICAL conductivity earth around the tunnel.The space model surrounding the gallery (up to 10 times the distance to the tunnel diameter) is divided into quadrilaterals whose conductivity can be changed. The Neumann boundary condition is considered for the inner and outer surface of the tunnel wall. The outer surface is far from the walls of the gallery.The code (Forward model) is programmed in COMSOL Script software using Matlab language. An input file was used that determines the location of each quadripole for each electrode array according data acquisition. Eventually, the apparent RESISTIVITY pseudosection is calculated from the code.An interpreted cross-section, obtained from manual inverse modelling using the code, shows good conformity with the results of the tomography obtained from the straight profile taken on the floor of the tunnel. The results also show that ERT is capable of investigating the RESISTIVITY changes near the surface of tunnel walls. The depth of the investigation is up to the tunnel radius.