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Showing 6 results for Soil Properties

H. Shakib, Gh. R. Atefatdoost,
Volume 12, Issue 1 (3-2014)
Abstract

An approach was formulated for the nonlinear analysis of three-dimensional dynamic soil-structure interaction (SSI) of asymmetric buildings in time domain in order to evaluate the seismic response behavior of torsionally coupled wall-type buildings. The asymmetric building was idealized as a single-storey three-dimensional system resting on different soil conditions. The soil beneath the superstructure was modeled as nonlinear solid element. As the stiffness of the reinforced concrete flexural wall is a strength dependent parameter, a method for strength distribution among the lateral force resisting elements was considered. The response of soil-structure interaction of the system under the lateral component of El Centro 1940 earthquake record was evaluated and the effect of base flexibility on the response behavior of the system was verified. The results indicated that the base flexibility decreased the torsional response of asymmetric building so that this effect for soft soil was maximum. On the other hand, the torsional effects can be minimized by using a strength distribution, when the centre of both strength CV and rigidity CR is located on the opposite side of the centre of mass CM, and SSI has no effect on this criterion.
A. Eslami, I. Tajvidi, M. Karimpour-Fard,
Volume 12, Issue 1 (1-2014)
Abstract

Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.
O. Farzaneh, F. Askari, J. Fatemi,
Volume 12, Issue 4 (12-2014)
Abstract

AWT IMAGEPresented is a method of two-dimensional analysis of the active earth pressure due to simultaneous effect of both soil weight and surcharge of strip foundation. The study’s aim is to provide a rigorous solution to the problem in the framework of upper-bound theorem of limit analysis method in order to produce some design charts for calculating the lateral active earth pressure of backfill when loaded by a strip foundation. A kinematically admissible collapse mechanism consisting of several rigid blocks with translational movement is considered in which energy dissipation takes place along planar velocity discontinuities. Comparing the lateral earth forces given by the present analysis with those of other researchers, it is shown that the results of present analysis are higher (better) than other researchers’ results. It was found that with the increase in AWT IMAGE, the proportion of the strip load (q) which is transmitted to the wall decreases. Moreover, Increasing the friction between soil and wall ( AWT IMAGE) will result in the increase of effective distance ( AWT IMAGE). Finally, these results are presented in the form of dimensionless design charts relating the mechanical characteristics of the soil, strip load conditions and active earth pressure.


S.a.o. Hosseini, M. Nasiri, M. Akbarimehr,
Volume 13, Issue 3 (9-2015)
Abstract

Harvesting of timber using ground based machinery is still a common practice around the world. Track and road building, and movement of machinery during harvesting operations cause soil disturbance. Therefore the aim of this study was to investigate the change in soil properties after logging operation on skid trails (2 years and 7 years after logging) and compare disturbed soil properties with control sampling (undisturbed soil). For this purpose, soil samples were collected from the skid trail and undisturbed area. Electrical conductivity, pH, organic carbon, moisture equivalent, moisture, total porosity and bulk density were determined on the skid trail and undisturbed area. Soil characteristics were examined in two ages (2 years and 7 years skid trail). There were crucial differences in the values of electrical conductivity, organic carbon, moisture, total porosity and bulk density from skid trail and undisturbed area in 2 years skid trail (p<0.05). But on 7 years skid trail, there were no significant differences in values of mentioned factors from skid trail and undisturbed area (p>0.05) except bulk density (p=0). It has been concluded that 7 years after logging, all soil properties except bulk density were completely recovered on skid trail. These findings have important implications for assessing the impact of skidders traffic and recovery time in skid trails.
Sedat Sert, Aybars Nafi Kılıç,
Volume 14, Issue 3 (4-2016)
Abstract

With the ongoing developments in numerical analysis methods, it is possible to model the soil-foundation-structure interaction and non-linear load-deformation behavior of soils in three-dimensional calculations. In light of these developments, the calculations of mat foundations can be made more realistically and economically by using advanced softwares, which take into account the interactions of these three components than the conventional methods. The aim of this paper is to present the effect of superstructure loading types on the analysis of mat foundations by using three dimensional finite element analysis results. Thirty six different models have been established to examine these effects on the internal forces and settlement behavior. The data of a 3-storey existing building has been used and superstructure loads have been modeled in different ways such as uniformly distributed loads, column loads and by modeling all building. The building has been modeled with a mat foundation having a thickness of 50 cm, 75 cm and 100 cm in seperate models. The mat and superstructure elements have been modeled either with 2D plate elements or 3D volume elements in different models. The “Mohr-Coulomb” material model has been used and soil properties have been represented as “normally loaded” and “overconsolidated”. Results for total and differential settlements and internal forces have been presented in figures and graphs. An important finding is the place where the maximum displacement occurs. It is very different when the load is transmitted by modeling the whole structure and it causes to have different internal forces and different placement of reinforcement. Another finding is that the biggest decreases in differential settlements are seen in column and building loading when the soil properties improved, while this effect remains very small in distributed loading. For bending moments, the biggest difference in comparison to the loading types is that the maximum moments are calculated in different places independent to the location of shear walls, when the load is simulated as a uniformly distributed load. It has been found that the superstructure loading type affects the settlement pattern and internal forces, so this effect must be taken into account.


Yones Sojodi,
Volume 14, Issue 4 (6-2016)
Abstract

The paper present the results of various experimental and numerical studies on slopes, small scale physical modeling of slope under surcharge load were performed in loose sand environment. Digital images were captured during the incremental loading from side of model simultaneously. The Particle Image Velocimetry (PIV) and 3D numerical model was applied to investigate the slope under surcharge loading and some of the other important factors that control the performance of piles are investigated. The factors of safety and location of critical failure surfaces of reinforced and unreinforced slopes obtained and compared for various slopes. For homogenous slope, it is found for stabilized slope with piles, the 3D failure surface shape in front of piles is triangle, unlike its conical shape in laterally loaded piles. The paper also studies numerically the effect of soft bound effect, soil properties, pile spacing, pile position and surcharge distance effects on stabilized and none stabilized slopes. The results indicate that the depth of soft soil layer from ground surface and its angles with horizontal direction has importance effect on optimum location of stabilized pile. Studies on pile space effects shows with increasing pile space, arching phenomenon didn’t developed and partial pressure of supported portion transferred to un supported soil portion and the potential failure volume of the slope becomes large.



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