Journal of Geotechnical Geology
Volume:16 Issue: 1, Winter and Spring 2020

The swelling potential is the most important factor on engineering and agricultural design of foundations on fine-grained soils which it can be cause expansion problems for these structures. So, providing the suitable views of swelling condition can help to solid designs. The presented paper, tried to understand the clayey soil’s swelling potential related to Marageh city in East Azerbaijan Province, NW of Iran; by using comprehensive laboratory tests (concluded 25 samples from 10 different sampling location) which included physicochemical properties, USDA class of soil and clay mineralogical aspects. The experiment results was used by regression analysis for formulate the swelling based on laboratory indexes (i.e., water absorption, porosity, density, Gs, SO4-, Cl-, pH, Casagrande limits, UCS, XRD and clay content). According to the analysis results, the studied soil’s (where classified as clay, clay loam and silty clay) swelling status is varied and located in moderate to high potential

Investigating of foundations actions on soil is one of the most important topics in geotechnical engineering. This behavior indicates the stability conditions of the foundation under structure loading on the foundation and soil responses. In this regard, the foundation’s behavior is affected by soil behavior and failure is likely. In recent years, the use of soil reinforced stabilization is considered as the most successful procedure to increase bearing capacity and reduce foundation’s settlements. In this paper by using finite element numerical modeling, attempted to evaluate the behavior of the geogrid-reinforced soil which conducted by Plaxis2D software. For this purpose, with the series of modeling, the soil- foundation behavior for both unarmed and reinforced conditions has been evaluated and the of geogrids performance was estimated. Based on the results of modeling, it has been determined that the geogrids has a good ability to improve and stabilize soil conditions.

As known the selecting the appropriate contractor is paramount importance to the success of civil projects which is even more important to urban construction projects in various cities. Thus, this study highlights the main criteria for selecting contractors for construction projects in urban area as cases study for Tehran city, Iran. The 19 criteria were identified based on field investigations and expert opinions which classified into six groups. The analytic network process (ANP) was applied on criterias to responses prioritization. According to the results of the assessment, the affordability with 0.0660 and compliance rate with 0.0599 importance score are ranked criteria for responses prioritization and selecting the appropriate contractor in Tehran city. The executive ability factor with 0.0144 score received the lowest attention in ANP model.

The superimposing of static and dynamic loads on such as machine foundation which are setting on the tunnels will cause differential and impermissible settlements. These settlements sometimes may reason irreversible damage to financial and human factors. This paper investigates the effects of the soil damping parameters, tunnel lining types and tunnel lining thickness on the circular foundation settlement under the influence of cyclic loads. PLAXIS 2D DYNAMIC is used as the FEM code to analyze models as well as investigating the effects of number of geogrid layers as a reinforcement element on the foundation settlement rested on the bored tunnel to obtain safe condition.

The purpose of this study is to investigate the effect of desert sand as a replacement on the tensile and compressive strength of concrete. To this end, a total of 180 cubic specimens (15×15×15 cm) and 90cylindricalspecimens (15×30 cm) were made with three concrete classes of C20, C25, and C30. Control samples (samples without desert sand) and samples containing 5%, 10%, 15%, and 25% sand were also produced. They were processed in mineral-free water at 7, 14, 21, and 28 days. They were then subjected to pressure and tension tests by a 200-ton digital concrete breaker jack. For the water absorption test, 15 cylindrical samples (7.5×15 cm) were made for C25 and 0%, 5%, 10%, 15%, and 20% desert sand. They were then tested after 28 days. The results showed that the compressive strength at the age of 28 days gradually increased by adding the sand. It reached the highest for C20 containing 10% sand. However, it reached the highest foe C25 and C30 containing 5% sand. Adding sand over 20% leads to decreasing compressive strength. The tensile strength of C25 and C30 concrete containing 5% sand and C20 concrete containing 10% sand was the highest compared to the control sample. Adding sand up to 10% leads to decreased water absorption, and then it increases after adding sand.

Knowledge of the earthquake behavior of embankment dams comes from four sources: observations made from the dam response during earthquakes, experiments conducted on prototype dams for determination of their dynamic properties, experiments conducted on reduced scale models of dams including shaking table and centrifuge testing and finally analytical studies. From numerical analysis point of view, two dimensional seismic response analyses is usually applied to seismic design of embankment dams. Evaluation of seismic behavior for different height of dam is important. Many embankment dams have been made in different height in the world that we have not general point of view about seismic behavior of them. To achieve this goal, Masjed Soleyman dam for a case study has been selected. Masjed Soleyman zoned rock fill dam with 177 m height was constructed and impounded in South-West of Iran in 2001. Finite Element model of Masjed Soleyman dam has been constructed and the Mohr-coulomb elastic-perfectly plastic constitutive model is taken into account to reflect the soil stress-strain relation. First, layer analyses have been carried out considering 12 layers in end of construction stage. Then, this analysis has been continued considering water table and weight of dam reservoir. 2 earthquake records have been applied horizontally to the bedrock for dynamic analysis. For study of mode of vibration and distribution of acceleration, 10 models have been used with different height. Then seismic response of earth dam due to some known earthquake has been investigated. These data were used to identify the modes of vibration of the dam. Result shows that First and second mode of vibration in Masjed Soleyman dam case to peak horizontal displacement and acceleration decreased in height of dam. Also changing of peak horizontal acceleration and peak horizontal displacement in height of dam depends on dominant mode of vibration, height of dam, properties of materials and frequency specification.

The presented study provide the numerical view and finite element (FEM) based modeling for earth-dam sealing curtains wall in earth-dam by using grout injection procedure. In this regard the plaxis software was used to estimate the variations and provide the simulation which is implemented in geometrical modeling, boundary conditions, assign materials properties, behavioral model, mechanical modeling and seepage analysis. Modeling conduced for two case groups related to before and after curtains wall design. According to the results of seepage analysis, it has been determined that when the sealing curtain is not applied, deformations due to stress, strain and pressure of the perforated water cause changes in the dam area and its expansion in sediments. On the other hand, the expansion of strain in the core range reflects the phenomenon of plastic behavior of the core and downstream, which is the result of in-situ stress and water pore-pressure in it.