ENGINEERING GEOLOGY
Year:2023 | Volume:15 | Issue:4|Papers Count:8

Despite the development of numerous excavation methods and reinforcement of tunnels, finding a proper method for stabilization of underground structures is a challenging task. The use of pre-reinforcement systems is an appropriate method to improve the status of the ground. In this study, the performance of umbrella system in Alborz tunnel in north of Iran has been investigated. Rock mechanics studies of tunnel running area have shown that parts of this tunnel have unstable capacity due to being located in weak zones. Therefore, the tunneling operation running is not possible in these areas. On this basis, umbrella pre-reinforcement system that can be used for loose and running ground are modeled numerically by Flac3D software. In this research, in addition to investigating the performance of umbrella system, the effect of geometrical parameters such as the angle of placement of pipes relative to the horizon and the distance between the umbrella system pipes was investigated. The criterion of investigating is the displacement occurred at the crown of the tunnel. The results of this study indicate that increasing the angle and decreasing the distance between pipes, cause an increase in stability and by using umbrella system, the vertical displacement of crown of the tunnel has decreased by 70 %.

The rock mass permeability is one of the most important parameters regulating to the groundwater flow through the fracture’s rocks. The permeability distribution is an important part of estimating inflow into tunnels. The common methods to rock mass permeability estimation such as lugeon tests are expensive and very time consuming. The use of intelligent methods to estimate or classify data, especially in engineering problems, has been common in recent decades. Many algorithms have been designed and optimized for this purpose. Support vector machines (SVM) is one of these methods. In this paper, using the SVM method, the Amirkabir tunnel has been classified from the permeability point of view. In order to optimize the parameters of this algorithm, random search method has been selected. The results show that the accuracy of modelling using this method based on experimental data is around 94.59%. Based on this result, amount 85% of tunnel length is classified in the low permeability category and water inflow into tunnel from this part of tunnel is negligible

Detecting the subsurface anomaly and characteristics of the soil such as weak layer is one of the most important parts of an engineering project. In this paper, the multichannel analysis of surface wave (MASW) is used to identify the subsurface anomaly. The effect of weak layer between soil layers is evaluated by simulating in ABAQUS software. In this regard, the effect of changes in the depth and thickness of weak layer are compared with the results of a two-layer soil media. In examining of thickness parameter, the values of 2, 4, 6 and 8 meters are chosen for thickness of the weak layer. Also, in the investigation of the depth parameter, the location of the weak layer at the depths of 2, 4, 6 and 8 meters are selected. The results showed that the presence of the weak layer caused discontinuity and jump in phase velocity spectrum of Rayleigh wave. It was determined that the position of jump is moved from higher to lower frequencies by increasing the buried depth of the weak layer. In accordance to the increase in the thickness of the weak layer, the number of jumps are increased, and these jumps are inclined towards lower frequencies.

In engineering works, especially in geological sciences, civil engineering and mining engineering, before or after the construction of structures, there are cases where it is necessary to determine the strength of stone or concrete. In this regard, changes in the use of the structure (change in load), unfavorable operating conditions, lack of time, lack of access to laboratory equipment and structural damage are among the reasons for assessing the strength of materials in situ. There are several methods for testing materials that are either destructive or have expensive and imported equipment. In this paper, using the new "Twist-off" test, the strength of 9 different types of stone and concrete with eight different strength classes has been measured. Also, while comparing the results with standard methods, calibration diagrams and equations required to convert the results of the "Twist-off" test to the compressive strength of the mentioned materials are presented. According to the results, to measure the compressive strength of ordinary concrete using twist-off test, the relationship y = 19.27x0.67 with a coefficient of determination of about 0.95 can be used. Also, for the rocks used in this research, by using the equation y = 27.87x0.52, the compressive strength of the mentioned rocks can be determined by using the twist-off test with an accuracy of 94%.

Due to construction of high-rise buildings and construction of underpass intersections and also due acceleration of construction of high-rise buildings in most metropolitan areas, deep and shallow excavations always bring advantages and disadvantages for engineers. During the construction of underpasses that are located below the groundwater level, no problem can disrupt the project development process as much as the presence of water problem ،due to this problem in the Baghodrat martyr underpass project of Kerman city to reduce groundwater ،different methods were studied. Eventually Valid scientific documents, the use of pumping wells and guidance to the intended location for drainage and stabilization of the well by nailing were confirmed. In this research, first numerical modeling Baghodrat martyr underpass of Kerman city using finite element method using Plaxis2D software and by changing the mechanical properties soil including internal friction angle, adhesion and permeability of soil as well as outlet pumping discharge, the maximum vertical subsidence The edge of the pit was calculated and the necessary analysis was performed in this regard. The results showed that increasing the angle internal friction and adhesion and soil permeability coefficient reduced sedimentation and increasing pumping discharge increased soil sedimentation. Then, using multilayer prosthetic artificial neural network in MATLAB software and Plexis software data as network entrance, the values of ambient subsidence around the pit in other cases have been predicted. Finally, an artificial neural network with a correlation coefficient of 0.982 is obtained, which indicates the accuracy and power of accurate prediction of real values.

Clay is a type of problematic soils that can cause problems such as swelling, settlement and significant deformation due to the absorption of water and moisture. Today, the use of available and waste materials to prevent environmental pollution to stabilize problematic soils is considered that one of these materials is sawdust ash. In the present study, the possibility of improving the properties of clay using sawdust ash has been assessed. For this purpose, sawdust ash with weight percentages of 3, 6, 9 was mixed with clay and then cured for 1, 7 and 14 days. In order to evaluate the geotechnical behavior of stabilized soil, Atterberg limits, standard compoaction, uniaxial compressive strength, direct shear, California bearing ratio (CBR) and consolidation tests have been performed. The results of the present study show that the optimum amount of sawdust ash is equal to 3% during the curing time of 14 days. In improved soil, the placticity index is 49%, the compression index is reduced by 40% and the maximum dry intensity is up to 14%, the uniaxial compressive strength is 65% and the shear strength at the moment of failure is on average 53.6% compared to not the stabilization state increased.

This study has reviewed and completed the database of landslides triggered by the 1990 Rudbar-Manjil earthquake (Ww=7.3), using previous studies, stereoscopic interpretation of aerial photographs, and checking satellite images (before and after the earthquake). We mapped 223 coherent landslides as polygons and central points using a digital elevation model (DEM, 12.5 m) by GIS software. A quantitative hazard zoning of the size (area and volume) of landslides was implemented based on controlling parameters by automatic linear regression (LINEAR) and geographically weighted regression (GWR) models. The controlling parameters include geotechnical group (cohesion and internal friction angle), topography (elevation, slope, aspect, and curvature), and seismic (distance from the fault rupture surface and the epicenter of the earthquake, the intensity of Arias, and the peak ground acceleration). The results showed that the quantitative zoning of the GWR model is more consistent with the size of existing landslides compared to the LINEAR model. The landslide area (LA) and landslide volume (LV) have a multimodal distribution compared to seismic and topographic parameters. Therefore, the nonlinear GWR model prepares a more accurate prediction of zoning than the linear regression model owing to the local effects of controlling parameters on the size of landslides.

Collapsible soils are among the problematic soils in nature that due to wetting, make many settlements so that according to research, the amount of settling can reach 1 to 2% of the thickness of the soil layer.If this type of soil is not identified, if structures are built on them, the constructed structure will be damaged if the soil saturates and changes in soil moisture. The existence of such soils in many parts of the world including Kerman province of Iran, necessitates the attention to study the behavior and characteristics of the collapsible soils. The aim of this contribution is to investigate the effect of butadiene rubber on the stabilization of collapsible soils. The tested fine-grained soils that have been sampled from two different sites were stabilized through injecting different percentages of butadiene (the number of experiments was 84). The ASTM D5333 Double-Consolidation Method, was applied in order to examine the stabilized soils on intact soil samples. The results show that the penetrations of butadiene rubber as well as the formation of butadiene rubber columns have led to reduction in soil collapse. Considering development of intelligent systems using prediction behavior of stabilized collapsible soils, the ANFIS model was used to predict degree of collapsibility of soil samples stabilized by injection Styrene Butadiene Rubber.