عباس مجدی

In the blast phenomenon, the explosives release a lot of energy, which causes damage and fractures the rock mass. One of the influencing parameters in the blasting results is the way the blast hole is charged. Power Deck blasting has been introduced as a blasting method to reduce or eliminate sub-drilling, optimize crushing, and reduce undesirable results. The purpose of this research is to investigate the impact of the Power Deck blasting method on the borehole pressure and damage to the rock mass compared to the conventional method. In this regard, the numerical simulation of a single blast hole was carried out using conventional and Power Deck methods by using LS-DYNA software. The results showed that in the Power Deck method, in the area of the air deck, the initial pressure of the hole is reduced compared to conventional blasting, and secondary pressures are produced, which leads to a reduction in the expansion of the hole along the air deck by 45% and increases the destruction in multi-stage. On the other hand, the generation of secondary pressures in the Power Deck method causes a 30% and 48% increase in rock mass destruction in the area of the bottom of the hole compared to the conventional method. As a result, the Power Deck blasting method improves the amount of expansion and destruction by using less explosive, which indicates the optimal use of the explosive energy.

The present work aims at implementing Response Surface Methodology (RSM) in order to generate a statistical model for Minimum Required Caving Span (MRCS) and estimate both the individual and mutual effects of the rock mass parameters on rock mass cavability. The adequate required data is obtained from the result of numerical modeling. In this work, various arrays of numerical simulations (480 models) are carried out using the UDEC software in order to study the rock mass cavability thoroughly. The effect of each individual parameter and their mutual effect on MRCS are investigated by means of ANOVA. ANOVA indicates that all the chosen parameters (depth, dip of the joint, number of joints, angle of friction of the joint surface, and joint spacing) highly affect MRCS. In other words, the results of ANOVA are in high agreement with the results of the conventional sensitivity analysis. Moreover, a combination of joint spacing and joint inclination has the highest mutual effect on MRCS, and a combination of undercut depth and joint spacing has the lowest effect on MRCS.

The mechanisms of deformation and failure of the structures in and on the jointed rock masses are often governed by the characteristics of the geometrical properties of joints. Since the joint geometry properties have a range of values, it is helpful to understand the distribution of these values in order to predict how the extreme values may be compared with the values obtained from a small sample. This work studies three datasets of joint systems (1652 joint data) from nine outcrops of igneous, sedimentary, and metamorphic rocks in order to determine the probability distribution function of the rock joint geometry properties. Consequently, the goodness-of-fit (GOF) tests are applied to obtain the data. According to these GOF tests, the Lognormal is the best probability distribution function representing the joint spacing, aperture, and trace length. The Cauchy is the best probability distribution function for the joint dip angle. It is found that the Cauchy distribution function is the best probability distribution function to represent the joint dip direction of igneous rocks, and the Burr distribution function is the best probability distribution function to define the joint dip direction of the sedimentary and metamorphic rocks.

Determining the hydraulic radius of the undercut in the block caving method is one of the key issues in this method. The hydraulic radius is directly related to the minimum caving span. In this research work, the rock mass cavability is investigated using the UDEC and 3DEC software. Since the factors affecting the cavability are very diverse and numerous, firstly, by 2D modeling in the UDEC software and examining the trend of changes in the minimum caving span, the most important factors including the depth, dip of the joint, number of joints, angle of friction of the joint surface, and joints spacing are selected for the final study. The variation trend of each variable is investigated by keeping the other variables constant (single-factor study) among various factors. In the second step, the minimum caving span for the five main factors and values is ​​determined in the single-factor study using the SPSS software and the multivariate regression method. Then the power function of the minimum caving span is chosen based on the selected variables with a coefficient of determination of 0.76. In continuation, a simple 3D model is built from the undercut. A linear equation is achieved between the results of the 3D and 2D modeling results in similar conditions. In a model with certain conditions, using the equation obtained from the numerical method, the calculated hydraulic radius of caving is 22.5 m, which is close to the result obtained from the Laubscher's empirical method with the same condition (24 m).

Prediction of the length of grout penetration and assessment of the groutability around the boreholes in the jointed rocks have a crucial effect on the planning and execution of grouting. Grout distribution in jointed rocks is a function of the geo-mechanical properties of rock mass, grout properties, and grout operational performance. This paper describes an analytical model based on the Newton’s second law, with the assumption of disk-shape model for the joints in order to calculate the maximum length of grout penetration in the horizontal and angled joints. It is shown that the proposed formulas can predict the length of grout penetration in rock masses with numerous joint sets as well. In order to validate the proposed model, it is compared with the existing analytical and empirical criteria, showing a very good accordance with their calculated results. Finally, the proposed analytical model is used to design the grout planning of a water conveying tunnel that is subjected to a heavy inflow. The design results in a successful filling of the vacant space behind the segmental lining and sealing the tunnel to stop the inrush water. These show that the model proposed in this paper can be successfully applied in practice.

The hydraulic jacking refers to the process of crack growth of the pre-existing joints in the rock mass under grout pressure above the minimum in-situ stress. Thus it is essential to understand the resistance behavior of the joints and maximum grout pressure. This paper describes a novel method for determining the hydraulic jacking occurrence in anisotropic rock mass based on the principle of fracture mechanics. This method is established on three stage developments: developing an equation in order to calculate the equivalent stress intensity factor at the joint tip, determining the fracture toughness by employing the Brazilian disc test with a loading rate of 0.1 MPa/s on the rock cored samples, and assessing the stability of joints using the maximum tangential stress criterion. By comparing the joint stress intensity factor and fracture toughness in the direction of rock anisotropy, the joint stability is evaluated. Then the maximum allowable grout pressure is analytically formulated as a function of fracture toughness in order to avoid the unwanted deformations in the joints (i.e. jacking) during grouting. In order to validate the proposed method, the data obtained from the boreholes used to construct water curtain at the Sanandaj Azad Dam in phyllite rocks are analyzed. Finally, it is concluded that the growth and expansion of the joints due to the instability under grout pressure leads to an increased cement take and the occurrence of hydraulic jacking. In addition, the proposed equation for computing maximum allowable grout pressure provides an acceptable agreement with the existing empirical rules and the results of the field data.

The uniaxial compressive strength (UCS) of intact rocks is one of the key parameters in the course of site characterizations. The isotropy/anisotropy condition of the UCS of intact rocks is dependent on the internal structure of the rocks. The rocks with a random grain structure exhibit an isotropic behavior. However, the rocks with a linear/planar grain structure generally behave transversely-isotropic. In the latter case, the UCS of intact rocks must be determined by a set of laboratory tests on the oriented rock samples. There are some empirical relations available to describe the strength of these rocks. Though characterization of transversely-isotropic rocks is practically a 3D problem, but these relations provide only a 2D description. In this paper, a method is proposed to provide a 3D description of UCS of transversely-isotropic rocks. By means of this formulation, one can determine UCS along with any arbitrary spatial direction. Also, a representative illustration of UCS is proposed in the form of contour-plots on a lower hemisphere Stereonet. The method is applied to an actual case study from the Kanigoizhan dam site located in the Kurdistan Province (Iran). Application of the proposed method to the phyllite rocks of this site show that the direction perpendicular to the dam axis exhibits the most anisotropic behavior. Hence, it is essential to take the strength anisotropy into account during the relevant analysis. The results obtained, together with the statistical variation of UCS, provide a practical approach to select the proper values of UCS according to the scope of the analysis.

During the production of hydrocarbon reservoirs and the injection process, pore pressure changes lead to reservoir compaction, which directly affects the petrophysical properties of the reservoir rock. Therefore, it is very important to recognize the changes in rock behavior and reservoir properties such as porosity and permeability which are significant. In this study, the effect of hydrostatic loading on petrophysical, geomechanical and structural properties of carbonate reservoir is investigated, which the investigation is followed by analyzing the porosity, permeability and pore size distribution. In order to investigate the changes in the geomechanical behavior of the carbonate reservoir, the compressional and shear wave velocities of two reservoir rock samples with similar geometrical and physical properties have been measured under different loading conditions. Scanning electron microscopy (SEM) images have also been used to examine the structural changes of rock samples. The results of this study show that under loading, permeability and porosity have a decreasing trend in 36.14% and 7.39% respectively in the last loading step. The study of compressional and shear wave velocities demonstrate that there is an increasing trend by increasing pressure, which it is due to the volume ratio of rock matrix to pore space. Combining the analysis of SEM images and pore size distribution shows that pores have become compacted, and the mean pore size has been reduced, in which this pore collapse and the placement of smaller particles among coarse particles have decreased porosity and permeability. Ultimately, understanding the changes in petrophysical properties along with their corresponding structural and geomechanical changes is very important in production planning of hydrocarbon reservoirs.

Today, oil industry significantly relies on the precise determination of rock reservoir properties, which reduces the costs and risks of production planning. The reservoir rock always is compacted by pressure drop of the reservoir, which rises effective stress, reservoir compaction and alterations of reservoir properties. As these pressure variations can considerably affect petrophysical properties, in this study, several carbonate reservoir rock samples with different fabric and porosity type (according to CT scan and Archie classification analysis) subjected to cyclic and short-term loading from 600 to 6000 psi. Their petrophysical and compressive properties including pore volume, permeability and compressibility were measured using CMS-300 apparatus. Moreover, structural analysis and heterogeneity of core samples were analyzed by CT scan images. By performing this study, it will be possible to identify the value of the hysteresis effect on the reservoir rock samples as a result of increasing and decreasing of the pressure during cyclic loading. The obtained results show that, pore volume and permeability are both decreased due to loading, whereas reduction of the permeability is several times than the pore volume ones. Moreover, this reduction of pore volume is less severe in vuggy porous samples that shows the effect of heterogeneity and porosity type on hysteresis. Also, the results obtained from the behavior of the reservoir rock under various pressure conditions can provide a suitable design for gas injection studies to enhance oil recovery and also natural gas storage.

Characterisation of the deformation behavior of the brittle rocks during loading plays a significant role on rock damage growth. There are a variety approaches to monitor the damage development. Among which the method of Acoustic Emission, due to its accountability, has attracted many researchers’ attention in recent years. The paper describes fracture mechanism of pseudo-rock samples by using Brazilian Test results. Hence, evolution of crack growth and its effect on tensile strength is the prime objective of this research. The work has been performed numerically by using UDEC (Universal Distinct Element Method) and RFPA (Rock Failure Process Analysis) for DEM and FEM analyzes, respectively. The effect of size and position of the artificial voids in disc-type samples on their tensile strength have been investigated. On this basis, several numerical models were constructed and analyzed. Typically, tensile cracks were initiated at the bottom or at the top of the voids, and then propagated parallel to the loading axis and finally reached to the sample surface. The results obtained by numerical methods have been compared with those obtained by Brazilian laboratory tests. Crack initiation, propagation, and coalescence produced by the numerical models have proven very good conformity with the experimental tests’ results. Finally, it has been concluded that by increasing the porosity, the corresponding tensile strength, count, and energy required to brick the rock will decrease exponentially. However, due to plane strain analysis of numerical software, tensile strength is estimated less than that obtained experimentally.

Tunnel boring machine and precast concrete lining (segmental lining) are two main parameters (that) should have been considered for tunnel excavating specially. By considering that the segmental lining is not uniform ring, investigation and estimation the behaviour of segmental lining are complicated. First, in this paper, we have been tried to introduced, the usual methods of investigation in segmental lining, as follow: Elastic, “Schulze and Duddeck”, “Muir Wood”, “Beam-Spring” and Finite Element models. As Beam-Spring model is acceptable and comprehensible, so developing this method in different ways, has been discussed completely. As joint is main and important factor in lining behavior, so segmental joint has been studied and the method of calculation joint stiffness has been introduced by this paper. Finally, this paper has been tried to present modulation and maintenance of beam-spring models, by two case-studies.

Unconfined compressive strength of rocks is one of the most important parameters in projects related to engineering geology, mining, geotechnics and rock engineering. For determination the unconfined compressive strength in laboratory tests, high-quality samples are necessary. However, such core samples cannot always be obtained from weak, thinly bedded and block-in-matrix rocks. For this reason, the development of predictive models for determination the mechanical properties of rocks such as unconfined compressive strength, seems to be an attractive study area in rock engineering. In this paper, fuzzy and statistical models were utilized to predict unconfined compressive strength of rocks based on data from the access tunnel in longwall mining. A total of 93 datasets of different rocks was used to develop the fuzzy and statistical models, from which, 75 datasets were considered for model construction and the rest was used for testing the models. Three parameters including Schmidth hardness, density and porosity were considered as input parameters. For evaluation of model performance, Root Mean Square Error (RMSE) and determination coefficient (R2) indices were used. For the fuzzy and statistical models, R2 equal to 94.3% and 87.9 and RMSE equal to 3.2 and 6.8, respectively. The results show that fuzzy model is significantly accurate comparing to the statistical model and its results are quite close to the actual values. Also, fuzzy model sensitivity analysis showed that Schmidth hardness is the most effective parameter on the unconfined compressive strength, whereas porosity is the least effective in this study.

More than 40% of infertilities are due to endometriosis. Ultrustructural and histochemical study of endometrium will help to clarify the etiology of endometriosis.

The aim of the present study was to investigate the ultrastructure and occurrence of apoptosis in endometrial cells of women with or without endometriosis.

In the present case-control study، endometrial specimens from 12 women without endometriosis (as control) and 12 women with endometriosis (as case) were examined. Specimens for control group were obtained from the patients that were referred to gynecology hospital for hysterectomy due to various reasons. In case group the endometriosis was diagnosed according to laparoscopy and endometrial samples were taken using pippel biopsy. The specimens from both case and control groups were processed for Transmission Electron Microscopy (TEM)، TUNEL reaction technique and morphometric studies.

The results show that endometrial epithelium lost its continuity in women with endometriosis and endometrial cells have euchromatic nucleus in comparison to those from non-endometriosis. There were several apoptotic cells in the luminal and glandular endometrial epithelium and stroma from endometrium of control group. However، apoptotic cells were rarely seen in the endometrium from women with endometriosis. The difference in number of apoptotic cells between two groups statically was significant (p<0. 001).

Regarding the ultrastructural characteristics of endometrial epithelial cells and comparison of apoptotic occurrence in control and case groups it is concluded that endometrial cells in endometriosis group have higher potential to survive and possibly implant.

Line 2 Tehran Subway Tunnel has been excavated by a special designed TBM with an open face shield. Then the prefabricated reinforced segmental concrete lining, type (8+1), has been erected as a permanent support system. Subsequently, cementitious grout was used to create a peripheral water sealing curtain to prevent inrush water into the tunnel. In this paper, the effort has been made to deeply investigate the principles and technology employed in grouting of and improving the alluvial deposits surrounding Line 2 Tehran Subway Tunnel. Hence, the results obtained from laboratory tests along with in-situ water pressure tests (WPT) were used to evaluate the influence of grouts on strength characteristic of the in-situ alluvial deposits. The results revealed considerable changes due to cementitious grouts in decreasing permeability and displacement, and the increase in strength characteristics of the surrounding alluvial deposits as well. Furthermore, for the first time, also in this paper, the grouted soil samples were used to analyze the grout distribution within the samples visually. The results were also used to establish an empirical relation within the parameters involved. Hence, an empirical equation has been proposed by which the percentage of quality of grouted soils can be estimated.

Flexural toppling failure occurs due to tensile stress caused by in-situ rock column moments. Observations and theoretical analyses carried out by researchers show that the total failure plane is perpendicular to the rock mass discontinuity plane. In this paper, to analyze the flexural toppling failure, each rock column is modeled as a cantilever beam. Then using the laws of the strength of materials, along with the limit of equilibrium, the safety factor is found. Although the result of this analysis is comparable with those of laboratory tests, their use in real slopes shows a safety factor more than what it has to be. This is due to stress concentration around and near the tips of structural defects in the rock mass. Calculation of the amount of stress concentration around structural defects, based on the laws of the strength of materials, is cumbersome and has not been observed in the analysis of flexural toppling failure. In this paper, for the first time, structural defects of in-situ rock columns, with a potential of flexural toppling failure, enter the analysis. In nature, structural defects in rock masses appear haphazardly and unevenly in different locations. However, due to brittleness of the rocks, the rock defects generally appear in the form of ended cracks. Keeping this in mind, to analyze rock columns with structural defects, we considered a single ended crack perpendicular to the column length resulting total failure. Hence, in this case, based on the theory of fracture mechanics, each rock column, with respect to the length of the crack, acts like a beam with two infinite ends. With the above presumptions and employing the equations of limit of equilibrium, we can find the forces and moments acting on the section involving the crack are found as follows: (1) (2) (3) Where:: Rock column weight.: The angle between the rock slope and the horizontal plane: Rock inter-column coefficient of friction.: Pore water pressure at the base of the rock column.: Rock column width. : Side length of the rock column.: Water pressure force at each side of the rock column.: Rock inter-column normal forces.: Rock inter-column shear forces (equal to respectively).: Distance between force points and the support.: Distance between force points and the support.Bending moment, compressive and shear forces cause, respectively, tensile, compressive, and shear stresses on the plane involving the crack, and their combined action produces the stress intensity around the structural defect of in-situ rock columns. Using empirical TADA functions, the “Stress Intensity Factor”, related to the above stress field is defined as follows:(4-a) (4-b) (5-a) (5-b) (6-a) (6-b) Where;: Normal stress intensity factor caused by the bending moment.: Normal stress intensity factor caused by the compressive force.: Shear stress intensity factor caused by the shear force. : Length of the crack.Since the factor of safety against failure is:, (7)if equations 1 to 6 are substituted into equation7, then the rock inter-column normal force is computed as follows: (8) To analyze a given slope against flexural toppling failure by using equation 8, first we should draw the total failure plane. Then rock columns are numbered, from the toe of the slope to the last column that has a potential to failure. Next, we substitute and for and (the force points between two columns) respectively, along with a prescribed factor of safety. Other related parameters, including the slope geometry, geomechanical properties of the rock mass and the ground water level are also taken into account. Now we apply equation 8 for the last column (column n) to calculate by letting. Repeating the calculations, knowing for column, we can compute and, finally for the first column, we can determine the value of. Knowing we can decide about the flexural toppling failure with the following conditions:If, safety factor of the slope is equal to the allowable safety factor.If, safety factor of the slope is less than the allowable safety factor.If, safety factor of the slope is more than the allowable safety factor.In cases 2 and 3 is substituted with a new value (in case 2 less than the allowable safety factor and in case 3 more) and the calculations are repeated. This process continues until the difference between two given consecutive safety factors becomes less than the acceptable error. In this case, the last assumed safety factor is considered equal to the factor of safety of the rock slope stability against flexural toppling failure.