Journal of Engineering Geology

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The study area is located in Jiroft district, Iran, and is a part of Sahand-Bazman volcanic zone. There are various landslide factors and the importance of each factor are identified qualitatively, based on previous studies and regional specifications. Three landslides were recognized in the study area using direct method (field work) and aerial photographs interpretation. One of these landslides is located in the vicinity of Mohammad Abad of Maskoon Village. The aim of this study is landslide hazard mapping using two integration methods that includes Fuzzy Logic and Hybrid Fuzzy-Weight of Evidence (Hybrid F-W of E). The obtained results of maps from both methods, show a good agreement especially in introducing  high hazard regions. The hybrid method is based on the occurred landslide points and is more rigorous, so hazard regions delineated by this method occupy smaller areas than the areas introduced by fuzzy model. Therefore, hazard maps resulted from Hybrid and Fuzzy methods, can be considered as minimum and maximum limits of landslide hazard in the area, respectively. 

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Today the effects of grouting are usually confirmed by the results of permeability tests but this method is not enough to show the changes in mechanical properties of rock masses. Although many investigators use the in situ tests for evaluation of rock mass mechanical property improvement. But this tests are time consuming and expensive. Grouting reduces the permeability and improves the condition of joints and ultimately increases the rate of rock mass classification in rock engineering. So with measurement of rock mass quality index values (Q-value) in cores obtained from grouted boreholes, the efficiency and success in improving the mechanical properties of rock mass can be showed. This paper for first time introduces Q-logging as a simple method to assess the impact of grouting in improvement of the rock mass quality. Here in, the results of Q-Logging in trial injection panels in the Bakhtiary, Bazoft and Khersan II dams have been examined. The deformation modulus were calculated from the Q-Logging for before and after of grouting. Results show that there is a good agreement between calculated rock mass parameters based on the Q-Logging method and the measured from in-situ test in the studied site. This agreement confirms the efficiency and applicability of the Q- Logging method for assessment of grouting success as well as the estimation of the rock mass parameters in grouted areas. Also it has been shown that the deformation modulus in weak rock mass with low quality has been more improved than rock mass with beater quality.

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One of the best approaches to reduce transportation problem is to use the underground tunnels. Therefore, Niayesh highway tunnel was performed by the New Austrian Tunnelling Method (NATM) in the northern part of Tehran and it includes north and south tunnels. The excavation of tunnels and other underground structures cause considerable changes in local stress conditions around structures that lead to surface settlement. In this research, surface settlement has been studied for five sections (CS-1 to CS-5) by empirical methods, numerical analysis and actual settlements. For the empirical and numerical methods, O’Reilly and New (1982) method and also finite element method (PLAXIS_2D software) have been used, respectively. On the basis of the obtained results, the numerical method in all sections (except section 3) is in agreement with the actual settlements. While, empirical methods have estimated the settlements more than actual values in those sections.  Also, the achieved results from the aforementioned methods show that the maximum settlement due to tunnel excavation is more than allowable settlement and it is in risk condition

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Introduction
Studying the effect of slope angle on bearing capacity of foundations on the slope in urban areas is a challenging problem that has been investigated by researchers for years. In general, the analytical approaches for solving this problem can be categorized into limit equilibrium, characteristics and limit analysis methods. In recent years, there have been studies for using the limit analysis within the framework of finite element method for geomaterials. In these studies, the soil mass is not considered as rigid and there is no need to predefine a failure surface for the slope. In the performed research, using the upper bound finite element limit analysis, bearing capacity of strip foundation on slope have been studied. This analytical method enables the use of the advantages of both methods of limit analysis and finite element analysis. In this method, the slip between the two elements is considered. In order to find the critical state of the failure, the rate of power internally dissipated is linearly optimized, by using the interior points method. The advantages of this method are the high convergence rate in comparison with other analytical optimization methods. The effect of different upstream and downstream slopes and foundation depths and also the influence of various mesh discretizations have been evaluated. Finally, the results are compared with those obtained from previous methods available in the literature.
Methods
The finite element limit analysis method is based on nodal velocities. Considering the principals of the finite element method and having the nodal velocities, the velocity at each node of the element can be obtained from corresponding shape functions. The rate of power internally dissipated in each element is defined by multiplying the strain rate on stress in each element. In this method, the slip between the two elements and the rate of internal power dissipated at each discontinuity of two adjacent elements is considered. For this purpose, in each node, four new unknowns’ velocities are defined. To remove the stress from the equations, and provide a linear relationship for linear optimization, a linear approximation to the yield function has been used. For this purpose, the Mohr-Coulomb yield criterion is estimated with a polygon in the stress space. Also, using the reduced strength parameter, the effect of the dilation angle is considered. According to the principles of upper bound limit analysis, the value of plastic strain rate is calculated from the flow rule. The velocity field in elements and discontinuities must satisfy the set of constraints imposed by an associated flow rule. In order to have an acceptable kinematics field, the velocity vectors have to satisfy the boundary conditions. These conditions include zero kinematics velocities along the vertical and horizontal boundaries of the geometry as well as negative vertical unit velocities and zero horizontal velocities at points underneath the rigid foundation.
Results and discussion
In order to calculate the bearing capacity of foundation, a set of different uniform and non-uniform mesh has been examined. The results obtained from different uniform mesh sizes indicate a certain divergence in the course of analysis. However, the results between the fine and very fine non-uniform mesh are closely related to each other and are converged. The obtained results show that, by increasing the internal friction angle, the bearing capacity has been increased. At high angles of modified friction, the effect of increasing the internal friction angle on the increase in bearing capacity is more in slopes with lower angles. By increasing the downstream foundation depth, the bearing capacity has been increased. This increase is more important in the case of slopes with lower angles. However, the upstream depth variations didn't present a significant effete on bearing capacity. In order to investigate the effect of upstream angle on the bearing capacity, the upstream mesh is also refined similar to the downstream. The obtained results indicate that variations of the upstream angle have a minor effect on the bearing capacity. This is of course true if the upstream slope is fully stable. The results of the proposed method in this study are an upper bound for the results reported by the limit equilibrium and displacement finite element methods. As seen in Figure 1, the suggested method predicts lower bearing capacities compared to rigid block limit analysis method and is indeed a lower bound for the classical limit analysis method. The finite element limit analysis with linear optimization has resulted in more bearing capacity than cone optimization. The bearing capacities, obtained from characteristic lines method depending to the slope angles, in some cases is more and in some cases less than those explored by the proposed method.
In this paper, the bearing capacity of foundation located on slope was evaluated by finite element limit analysis method. In this regard, the effects of different downstream and upstream angles of slope and foundation depths and also, the effect of various mesh discretizations on the bearing capacity were studied. It is shown that an increase in the downstream angle causes a decrease in the bearing capacity and an increase in the downstream foundation depth leads to an increase in the bearing capacity.  However, the upstream angle and upstream foundation depth were not much effective on the bearing capacity.
 

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Introduction
Grouting is one of the most widely used methods of soils improvement in which pressurized grout penetrates in the voids, of the soil. In the grouting method, in addition to reducing the permeability, shear strength and stiffness of the soil increase significantly. However, application of this method in projects such as dam construction and soil improvement requires the use of a large volume of grouting materials in order to satisfy the design criteria. In more recent years, due to the economic and environmental issues, in the case of cement-based grouts, replacing the whole or a portion of Portland cement with other materials has been experimentally investigated. A special type of kaolinite clay called metakaolin has recently been used in concrete, which has yielded interesting results. However, few studies has been conducted on the use of metakaolin in cement-based grouts. Such that, its effect on the mechanical behavior of the grouted soil are not well understood. Accordingly, in the present study, the mechanical behavior of a type of sandy soil grouted with different combinations of Portland cement and metakaolin was experimentally investigated in laboratory scale.
Material and methods
Different materials used in the present study including sand, cement, metakaolin, bentonite and water were selected based on the standard criteria and with the aim of better interpreting the test  result and their differences due to considered influencing factors. Sand was obtained from Malayer Shushab river bed. According to the Unified Soil Classification System (USCS), it is classified as SP. Ordinary Portland cement was used in this study regarding to its widespread application in the practical works. The metakolin is classified as class N pozzolan according to the ASTM C618. Another constituent material of grout is bentonite which is produced by Iran Barit factory as sodium-calcium bentonite. Its liquid limit and plastic index are 296 and 262 percent, respectively. The water used to prepare the grouts was provided from Hamedan drinking water, which according to ASTM C94 has the required quality for grouting operations in laboratory.
The device for grouting specimens was developed at the Soil Mechanics Laboratory of Bu-Ali Sina University during the present study. It equipped with grouting pressure control system and tool for keeping grout in homogeneous conditions during the grouting operation into specimen. The samples were prepared with 0, 5, 10, 15, 20 and 25 percent substitution of cement with metakaolin. Curing time of grouted samples was considered as14 and 28 days.
In order to investigate the factor affecting stress-strain behavior of the grouted sand, the samples were sheared using advanced triaxial apparatus. After passing considered curing time, the samples were sheared considering three levels of confining pressures of 50, 100 and 200 kPa and by applying axial strain rate of 1 mm per minute. For each test, the maximum deviator stress and its corresponding axial strain were recorded. In addition, for studying post peak behavior of grouted soil, for every one of tests, average ratio of deviator stress to the axial strain as softening modulus, was calculated from the deviator stress-axial strain curves.  The moisture content of the samples was also measured according to ASTM D2216 at the end of tests. In the following, the role of different factors influencing stress-stain behavior of grouted sand including; confining pressure, ratio of water to the mix of cement and metakaolin, percentage of metakaolin, curing time and moisture content were investigated.
Results and discussion
Figure 1 shows the effect of metakaolin as alternative of a portion of cement on maximum confined compressive strength and its corresponding axial strain.
For the samples confined by pressure of 50 kPa the maximum confined compressive strength is almost constant by replacing cement with metakaolin up to 10%. However, the amount of axial strain corresponding to the maximum compressive strength of the specimens increases by 6% (Figure 2). For 25% replacement, the maximum confined compressive strength of the samples decreases by 17% compared to the initial state (pure cement). In contrast, the axial strain value related to peak state of most samples has been increased by 4% in comparison to the initial state.
 
In the case of confining pressure of 100 kPa, by replacing up to 10%, the mean confined compressive strength of the specimens was almost constant. However, the amount of axial strain corresponding to the peak state of the specimens has been increased by a maximum value of 18%. For 20% replacement percentage the compressive strength of the specimens has been decreased by about 15% compared to the initial state. However, in the range of 20 to 25 percent, the reduction process has slowed down, which can be due to various factors such as the effects of sample densification during further increase of metakaolin. According to Figure 1, it can be seen that in the range of 20 to 25% substitution, the amount of strain at failure state increased by an average of 40%, which indicates that the sample is more deformable.
In the case of confining stress of 200 kPa, by replacing 10% of the cement with metakaolin, maximum confined compressive strength and its corresponding axial strain, has been increased by approximately 5 and 14%, respectively. With increasing cement substitution up to 25%, the resistance of the specimens decreased by 8% compared to the result of sample grouted with pure cement. Although, axial strain at peak state has been increased by 28%. From the Figure 1, it is obvious that increasing in confining pressure yeilds a considerable increase in the maximum compressive strength of grouted soil. Besides, post peak behavior of grouted soil is also affected significantly by confining pressure. Such that an increase in confining pressure leads to decrease in softening modulus. On the other word, grouted soil displays a more deformable behavior. It should be noted that these aspects of grouted sand cannot be described by unconfined test. However compressive strength of the grouted soils in the majority of case, has been evaluated based on the unconfined test results. 
Conclusion
The aim of this study was to investigate, in laboratory scale, the mechanical behavior of sand grouted with cement-based grout and considering different percentage of metakaolin as an alternative for a portion of cement. The soil samples were grouted using a specific device developed during present study. After passing curing time the samples were sheared using triaxial apparatus by considering three levels of confining pressures. The main findings of this experimental research are as follows:
- Replacing 10% of cement with metakaolin, increases deformability of grouted soil, without reducing compressive strength. Deformability of grouted soil increases with adding more percentage of metakaolin however, in this case compressive strength decreases.
- By increasing confining pressures, more values of metakaolin can be used instead of cement in the grout.
- Increasing confining pressure, increases compressive strength, increases deformability and deceases softening modulus at post peak behavior.
- Shear strength parameters of grouted sand is affected by adding metakaolin into the grout. Increasing the percentage of metakaolin results in small changes in the internal friction angle of the grouted sand, however, the amount of cohesion decreases.