Journal of Geotechnical Geology
Volume:16 Issue: 2, Summer and Autumn 2020

Application of soil nailing in stabilization of excavation operations in urban area’s constructions is most flexible and capable techniques for earth retention under soil mass instabilities. In general, the implementation of the soil nailing method is step-by-step, and this issue itself causes various and step-by-step changes in the excavation area. Therefore, by studying these stepwise deformations, it can be obtained the development of soil’s failure mass step-by-step. In this regard, presented article tried to investigate the stepwise deformations’ analysis in soil nailing operation in excavated soils using finite element numerical method and Plaxis2D software. The modeling was performed during four drilling stages and the changes in the slope stability as well as the deformations’ expansion in slope mass (sand and clay) were investigated. Based on the simulation results, it has been determined that with increasing depth, the degree of confidence in the slope (safety factor) for 2 different arrangements decreases step-by-step and the plastic area increases towards the bottom of the pit. But the nailing wall shows a good ability to curb instability.

Liquefaction is one of the main topics of seismic geotechnics. The effects of liquefaction on structures and installations during an earthquake can be very destructive. In the two earthquakes Alaska and Niigata Japan in 1964, spectacular examples of earthquake-induced failures, such as rupture of slopes, deformation of foundation in buildings and bridges, and the floating of buried structures a result of the flow of soil bed occurred. In liquefaction in general, soils tend to be denser when non-adherent, saturated and loose soils are exposed to earthquake vibrations. However, in certain granulation ranges, drainage is somewhat slow, as the rapid fluctuations in the soil due to lack of drainage will necessarily increase the pore pressure. Increasing pore water pressure results in a reduction in effective stress, which results in reduced shear resistance of the soil. Based on the relationship between the geostatic stresses in the soil, the increase in pore pressure may reduce the effective stress in the soil, which results in low or even zero shear strength and, consequently, Soil flows into fluid state, which is called liquefaction. In this research, we will study this phenomenon in the East of Urmia plain using the Japanese specifications for highway bridges 1999. The basis of this method is the evaluation of the liquefaction potential, by comparing the liquefaction resistance assessed from the soil SPT with the shear stress ratio induced by the earthquake to the normal effective stress from the earthquake. Of the 6 study boreholes, only one of the boreholes with high-liquefaction risk was evaluated. So the risk of liquefaction is very low. In general, the southern part of Urmia region requires more geotechnical studies due to the density of existing industries and roads, and also geophysical studies such as the use of shear waves.

Soil improvement can be expressed as one of the most important applied achievements of geotechnical engineering to improve the resistance conditions and properties of soil mechanics in a wide range of soil materials. The purpose of the improvements is to achieve proper resistance of soils (especially loose soils) to failure, which can cause serious damage and costs to construction projects. The micro-pile is one of most effective stabilization methods, which is used in the materials’ limitations and it is more economical than other techniques. The present study is based on investigation on the micro-piles’ performance to the improvement of sandy soil’s slope under dynamic earthquake loading. Methodologically, the finite element numerical method and Plaxis3D software have been used to implement the loading conditions and evaluate the deformations that have occurred in loose body of slope. The modeling process can be divided into two modeling groups, including slope with and without reinforced by micro-piles which is indicate the improvement process based on deformation reduction by stabilization technique. According to the results of the numerical simulation, it has been found that the use of micro-piles can be very effective on slope stability of the excavated trench in loose soil.

The Covid-19 pandemic was affected the human-environment relations which caused several consequences on ecosystems like environmental pollution changes. In this regard, the presented article is discusses the environmental impacts of coronaviruse spread in all over the world. For this purpose, an overview provided based on published articles about environmental effects of Covid-19. The key concept of the presented works is preparing a suitable reference for investigating the environmental influence of Covid-19 pandemic.

Pozzolan is an additive to cement clinker that if added to the high quality cement and concrete, it can be effective in enhancing the quality of cement and concrete resulting from high quality controlled precision and repeated sampling and continuous testing. Concrete creates the cement-free concrete without any additives. Documentary reports and rigorous scientific studies have shown that good pozzolan can, in addition to increasing the chemical resistance of concrete, eliminate the defects caused by the use of conventional cement in concrete and due to the diversity of water and soil use in different areas. In this study, the effect of natural pozzolan in different grades of cement on the mechanical properties and permeability of concrete at 7 and 28 days of age is investigated. It was found that with increasing cement grade, the water absorption rate of concrete increased. Also, the effect of pozzolan on the permeability of concrete samples is increased by increasing the pozzolan water absorption rate. Also, the effect of cement grade on the compressive strength of concrete was found to decrease with increasing concrete grade. Today using alternative sources in concrete productions is important, due to its economical and environmental considerations. Pozzolans are one of these resources which decrease the environmental pollutions and production costs of concrete structures.