نشریه زمین شناسی مهندسی ایران
سال پانزدهم شماره 3 (پاییز 1401)

Static parameters are one of the most important parameters in estimating geomechanical properties. Determining these data is very costly in in-house studies, so they are not normally available or limited in scope. Hence, many researchers have tried to provide empirical relationships to estimate these parameters from other characteristics. The aim of the present study is to evaluate the parameters of the Young Static Modulus and the Uniaxial Compressive Strength of Aghchagili limestone based on physical and dynamic properties using multiple regression. For this purpose, ten blocky samples from the surface outcrops of the formation were prepared, and a 18 cores were obtained from them, and various physical, mechanical and wave velocity tests were carried out on the specimens. The results of this study showed that three different variables of density, compressive velocity and dynamic yang modulus have a better relationship with Uniaxial Compressive Strength than different physical and dynamic parameters. Also, for estimating the static Young Modulus, porosity variables and dynamics of Young's Modulus yield more acceptable results.

In this paper, stability analysis of the slopes on Sungun mine was investigated. Sungun mine located in East Azerbaijan province, 45 km north of Varzaghan city. In order to investigate the stability coefficient and the rate of displacement on the slopes, three sections were selected and analyzed by numerical and equilibrium methods using SLIDE and UDEC models. The results showed that the coefficient of slope stability against failure in static conditions is more than 1.4 and in dynamic conditions with cosidering of the design based acceleration (DBA) of 0.35 g, it will be in the range of 0.92 to 1.2. In the case of applying acceleration of 0.42 g, the safety coefficient decreased to 0.8 and 1.05 and in most of the mine area, especially by Janbu method, it will be less than 1 and occurance of instability in wide range of the studied mine area is possible. However, in the extraction benches even with the application acceleration of 0.35 g, a limited chance of failure is possible. Based on the numerical analysis results, the displacements in the western part of the mine (downstream of the mine slopes) are generally higher than the eastern part of the mine. The maximum dynamic displacement in DBA of 0.42 g will be happen at section 2 (middle part of the mine) with the amount of more than 40 cm. In the entire of the mine area, the occurrence of toppling failure is dominant.

Mineralogy and physical and mechanical properties of rocks used in the production of aggregates are the most important parameters for deciding on the method of their use for various engineering purposes. Concrete is one of the products produced in the construction industry that has the highest consumption of stone in the form of sand gravel materials in its building. In this paper, the effect of mineralogy as well as physicomechanical properties of aggregate on the compressive strength of concrete with C25 strength class has been investigated. They are exposed in the east of Ardabil (Iran). In order to conduct research, 20 samples of mines and sand workshops active in the harvest area and physical and mechanical tests and lithography and mineralogy were performed. Then, the ratio of concrete components by ACI method was determined so that the ratio of water to cement was kept constant in all designs and no additives were used. To analyze the results, the rock masses of the region were divided into four categories based on the type and mineralogical composition and the effect of their physicomechanical properties on the strength of concrete in each category was investigated separately. The results show that the strength of concrete made with andesitic rock mass (class II) has the highest value and class IV (dolomitic rock mass) has the lowest value. Also, concrete made of limestone (class III) depending on different characteristics Mineralogy and physicomechanics offer a wide range of resistances.

The use of lightweight stone materials and alkaline adhesives to replace gravel and ordinary Portland cement in concrete production prevents the emission of a significant portion of greenhouse gases, saves energy, and reduces the dead load of the structure. In this study, porous coarse-grained lava rock has been used to reduce the density of concrete, as well as slag and fly ash, as alternative materials to ordinary Portland cement in concrete production. Alkaline activation of the pozzolans was performed by solutions of 14 M sodium hydroxide and sodium silicate with a mass ratio of 1: 2. Chloride ion invasion, sulfate invasion, and the combination of sulfate and chloride invasion are on the research laboratory agenda. Concrete with alkaline slag and different ratios of slag and fly ash for alkaline activation and hydrated Portland cement have also been selected for comparison. According to the obtained results, Portland cement concrete tolerated the fastest deterioration against combined aggression with a reduction of almost 10% in compressive strength, the highest compressive strength was 55 MPa slag concrete, and with increasing fly ash replacement, the short-term mechanical properties are weakened, but with decreasing water absorption loss, on average, by about 12%, the long-term durability and protection of reinforced concrete increases.

Geopolymer concrete was proposed in order to eliminate the disadvantages (such as low strength and environmental damage) caused by the use of ordinary concrete in structures. In making this type of concrete, processed geopolymer materials from mineral sources such as slag and nanosilica replace cement and produce strong geopolymer concrete. In this laboratory research, a mixing design was made of control concrete containing Portland cement. Then geopolymer concrete was produced in three designs. The first design contains 100% of the slag of the composing furnace and the second and third designs contain 92% of the slag of the composing furnace and 8% of nanosilica, respectively, containing 1 and 2% of polyolefin fibers (4 mixing designs in total). Then, modulus of elasticity and tensile strength tests at 7 and 28 days of processing time at room temperature were performed on concrete samples. SEM test was performed on concrete samples at 90 days of age for validation with other results. The results indicate that increasing the curing age of concrete improved the results. In the modulus of elasticity and tensile strength test, the addition of fibers to geopolymer concrete at the age of 28 days, improved the results in Figure 19 (2% of fibers) compared to Figure 2 (no fibers) by 21.19 and 24.07%, respectively. Increasing the fibers improved the results of tensile strength tests and modulus of elasticity of geopolymer concrete compared to control concrete. The results of the SEM test overlapped with the results of other tests.

One of the indicators for evaluating the performance of a tunnel drilling machine is predicting the penetration rate of this machine. There are various methods and relationships for predicting the penetration rate, each of which has its own characteristics and are presented based on the parameters related to the rock mass and the characteristics of the machine. In this study, genetic, artificial immune system, dolphin echolocation and grey wolf algorithms were used to predict the penetration rate of TBM. In this regard, the database consists of 153 data (122 data for train and 31 data for test) including parameters of intact rock such as strength and brittleness and rock mass characteristics such as distance between planes of weakness and orientation of discontinuities along with TBM machine performance in Queens tunnel has been collected. Mean square error (MSE) and square correlation coefficient (R2) have been used to estimate the error rate between the developed methods. Considering the key parameters of rock mass and intact rock and TBM, relationships to predict the penetration rate are presented and based on statistical analysis, the best relationship is selected. The results are compared with the real data and the results of other models show that the values penetration rate predicted by the genetic algorithm with MSETrain=0.012, MSETest=0.02, R2Train=0.9319 and R2Test=0.8473,has acceptable accuracy compared to other methods.

In this study, a discrete element method based on linear parallel bond model (LPBM) has been used to investigate the growth path of cracks and the amount of force required to create it. The formation of cracks in this method is due to the breaking of the bond between the particles, which forms macro cracks by joining the microcracks. It was found that the average normal forces for breaking the bond in wing crack are about 11 and 30% in oblique and coplanar cracks by investigate the load on the coal sample containing pre-existing cracks, therefore, the growth of wing tensile cracks in the sample is due to the low value of normal forces. The value of shear force required to overcome the parallel bond of particles in oblique and coplanar cracks is about 7.5 and 3.5 times in wing crack, respectively, in order for crack propagation, it is necessary to break the shear bond between the particles in the oblique and coplanar crack path. The average shear force required to break a bond in the coplanar crack path is about 47% in the oblique crack path, which makes the coplanar crack faster than the oblique crack. The wing crack has the highest value in terms of length compared to other secondary (induced) cracks before the peak point (in stress-strain curve), and this causes the pre-existing cracks in the coal seams to be joined using wing cracks.

 One of the subjects of geotechnical engineering is soil bearing capacity, which is a function of the engineering properties of subsurface deposits and foundation characteristics. In this study, the results of 78 exploratory boreholes drilled in Mahshahr Special Economic Zone and Bandar-e-Imam were used to produce engineering geological maps with the aim of determining the soil bearing capacity in that area. The result from the boreholes shows that the sediment of the area is mainly clay and to a lesser extent silty clay and silty sand. After determining the soil classification, engineering parameters were determined based on laboratory test results. Then by using Hansen's formula and considering the allowable settlement of the foundation, bearing capacity was calculated for square foundation (1×1) and (2×2) meters, strip foundation with buried unit depth and a mat foundation (10×20) meters with buried depth one and two meters. By using the ArcGIS software, the load capacity map of the study area was produced and result shows that the allowable bearing capacity in this area varies between 0.40 to 0.98 (kg /cm2) and the northern area has higher load capacity than other area.