JOURNAL OF ENGINEERING GEOLOGY
Year:2017 | Volume:11 | Issue:3 |Papers Count:8

Earth-fill dams stability in steady state seepage condition is very important, especially during earthquakes. Numerical software analyses require accurate and realistic modeling of construction stages. Since earth-fill dams are constructed in different layers, so these conditions should be considered in software modeling to achieve a reasonable design. In this study, an earth-fill dam is modeled in PLAXIS software and the effects of the number and shape of layers are studied in dry and steady-state conditions. Obtained results in static and pseudo static analyses show that modeling of earth-fill dams with different layers has significant effects on shear stresses and horizontal displacements. For example, horizontal displacements and shear stresses, increase at least 50% and 17% respectively, in comparison with single layer models. According to the obtained results, it can be mentioned that modeling of an earth-fill dam in the layered model and rather in inclined layers are more reasonable.

Geotechnical engineers, in many cases face with low strength or high swelling potential of clayey soils. Stabilization methods are used to improve the mechanical properties of this type of soils. Lime and cement are the most popular materials used in chemical stabilization of clayey soils. If sulphate exists in the stabilized clayey soil with lime, or if soil is exposed to sulphates, problems such as strength reduction and swelling will occur. Reuse of industrial residual such as Rice Husk Ash (RHA) can be beneficial from the economy point of view. RHA includes a proper amount of silica with high specific surface area which is very suitable for activating the reaction between the soil and lime. In this paper, chemical stabilization of gypsum clays using lime and RHA is addressed.Sulphates exist in the constitution of the soil. Unconfined compression strength and swelling potentials of the stabilized soil are evaluated. The results of this study indicate that RHA has positive impacts on improving mechanical properties of the gypsum clays stabilized with lime. From the view point of strength and swelling characteristics, and economy, addition of 6–8% lime and 8-10% RHA as an optimum amount is recommended.

In the narrow geosynthetic-reinforced retaining walls a stable rear wall exists in a short distance and there is no enough space to extend appropriate length of reinforcements. In this case, the probability of overturning of retaining wall increases especially when subjected to earthquake loading. To increase the stability of the wall, reinforcements may be connected to the stable rear surface. Alternative solution is the utilization of full-height cast in-place concrete facing in order to resist the earth pressure by combined actions of reinforcements pullout capacity and facing flexural rigidity. One of the main questions about this type of walls is the portion of earth pressure resisted by the facing.In this study, the seismic earth pressure of narrow geosyntheticreinforced backfill on rigid facing was evaluated using limit equilibrium approach and horizontal slices method. The critical failure surface was assumed to extend linearly from the wall toe to the rear surface and then moves along the interface of the backfill and rear surface up to the backfill surface. The effects of various parameters such as wall aspect ratio have been investigated. The obtained results show that the applied soil pressure on wall facing will be increased with depth in the upper part of the wall according to the Mononobe-Okabe equation, but its pattern is inversed in the lower part of the wall and it decreases until it reaches to zero at the wall toe. The results of analyses indicate that the attracted soil thrust by the facing increases with lessening of backfill width.

Rock anisotropy plays an important role in engineering behavior of rocks. Slates are anisotropic rocks which have long been used for gable roof, floor tiles, borrow materials, and other purposes. The slates studied in this research are calcareous and have a porphyro-lepidoblastic texture. To determine the role of the anisotropy on the tensile strength and fracture pattern, two variables including Y (the core axis angle to foliation) and b(the angle between the axis of loading and foliation) in the Brazilian tests were used. The angles were selected at 15o intervals.Thus, for both Y and b, seven angles of 0o, 15o, 30o, 45o, 60o, 75o, and 90o were selected (i.e., there are 43 possible modes). In order to name and examine the failure pattern, 11 models were proposed. The average value of the failure strength for the three stations varies from 3.21 MPa to 20.94 MPa. Based on the obtained results, there is a direct relation between the average tensile strength and density. A comparison between Brazilian test data under dry and saturation conditions shows that the saturated Brazilian tensile strength is 30.8% less than the dry Brazilian tensile strength. Moreover, the changes in fracture length with thechanges inψ and b indicate an inverse relation. Eventually, the average of tensile strength(st) and strength anisotropy index (Ia) demonstrates thatthe influence of orientation angle (Y) is much larger than that of foliation-loading angle (b).

Landfilling has been recognized as the cheapest method for the disposal of municipal solid waste and as such has been the most used method in Iran. Landfill site selection is a complex process involving social, environmental, and economical parameters as well as government regulations. The aim of this study is to propose suitable sites for burial municipal waste in the Ardebil using Multi Criteria Decision Making (MCDM) method, field investigations and environmental study. In the first stage, restriction areas are identified and eliminated using integration Geographic Information System (GIS) and Analytical Hierarchical Process (AHP). Then other criteria categorized and weighted using AHP method. By overlapping all of criteria maps 12 sites are recognized as landfill prone areas. In the second stage, eight sites were eliminated during the site investigations study and remining 4 sites were introduced as suitable sites. Finally site No.6 is proposed as the most appropriate site based on the environmental and social economical considerations were carefully evaluated with Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method.

In recent decades many researchers have studied on the damage assessment of structures after a seismic event. To assess the damage of structures under an earthquake, it is so important to study the correlations between earthquake parameters and damages of the structures. A lot of seismic parameters have been defined by researchers to characterize an earthquake. Spectral parameters of an earthquake convey a variety of information about ground motion, so they can properly characterize an earthquake. Also a lot of damage indices were proposed by researchers to quantify the damage of the structures or to rank their vulnerability relative to each other. Park-Ang index is one of the best indices to describe the damage of a structure. In this paper, the correlations between spectral parameters of earthquakes and Park-Ang indices are studied. Three RC frames with different height are analyzed under far-fault earthquake records by nonlinear dynamic analyses. The correlations between spectral parameters and Park-Ang indices of the frames are calculated. The results show that in all the frames most of spectral parameters have strong correlations with damage intensity. In order to estimate the damage potential of an earthquake, some spectral parameters which have high correlations with damage intensity can be proper indices. Housner intensity, acceleration spectrum intensity and velocity spectrum intensity are shown to have strong correlations with damage intensity. In this paper, a new spectral parameter which has high correlation with damage intensity is achieved.

Uniaxial compressive strength is one of the most important features to describe the resistive behavior of rocks which is used as an important parameter in the design of structures especially underground openings. The determination of this parameter using direct methods such as ordinary uniaxial compressive strength tests is costly and time consuming, and also sometimes preparation of standard samples in many rocks is difficult. In such cases, the implementation of the simple non-destructive tests and using empirical relations can increase the evaluation speed and reduce costs. These relations even regional or local (for example within a geological formation or a single lithology) can help in the estimation of these parameters in order to be used in geotechnical projects. In this study, samples of existing limestones in north of Saveh were prepared and uniaxial compressive strength, point load, Schmidt hammer and shear wave velocity tests have been performed. Then, by the statistical evaluations of the results, the empirical relations between uniaxial compressive strength and the results of other tests have been obtained. Finally, to evaluate derived relations, they have been compared with the same relations.The comparison between the predicted and observed values of uniaxial compressive strength represents the validity of obtained empirical relations. The application of the proposed relations for limestones in the study area and those with similar geological conditions will provide acceptable results.

The results of an ongoing FEM parametric study are presented regarding the dependence of the resulting piled raft behavior under lateral load and combination of loads on pile diameter, pile length, arrangement of piles and raft thickness. Taguchi method with Analysis of Variance (ANOVA) was employed to calculate the contribution ratio of these factors on the lateral displacement of piled raft. The obtained results of this study show that the pile diameter is an effective factor in horizontal deformation of the piled raft under pure horizontal load. However, in the case of load combinations, the pile length has the highest participation ratio in reducing the horizontal deformations.