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It is the objective of the present study to present a methodology for determining the horizontal seismic coefficient for soil-nailed walls based on numerical non-linear dynamic analysis. As a first step, two verification tests were simulated in order to validate the numerical modeling methodology and assumptions both in static and dynamic modes. The static validation phase involved simulating the soil-nailed wall in the Clouterre project and comparing numerical and measured profiles of horizontal displacement after excavation. The dynamic validation phase included a shaking table test on a soil-nailed wall, followed by a comparison of numerical and experimental profiles of the horizontal displacement of the wall at the end of the seismic loading. Afterwards, an in-depth explanation of the numerical modeling methodology used to calculate the seismic coefficient for soil-nailed walls was provided. Thereafter, an extensive parametric study was conducted to examine the effects of various factors on the horizontal seismic coefficient, including the wall height, soil relative density, soil cohesion, earthquake frequency content, ground surface acceleration, and altering the soil nailing design. In the parametric study, three earthquake acceleration records were used: Kocaeli, Avaj and Chi-Chi. The results of the parametric study showed that the ratio of the maximum horizontal seismic coefficient to the maximum ground surface acceleration (khmax/PGA) decreased on average with the increase in the wall height, the predominant frequency of earthquake motion and the maximum ground surface acceleration. Furthermore, the results indicated that the khmax/PGA ratio increased with an increase in soil relative density. Moreover, the ratio increased slightly as soil cohesion increased. Additionally, it was found that modifying the soil nailing design by increasing the diameter, reducing the horizontal spacing, and increasing the length of nails did not significantly alter the khmax/PGA ratio. The calculated horizontal seismic coefficients (khdesign) resulted from the parametric study ranged from 0.18 to 0.46 of the maximum ground acceleration (PGA), which is less than the commonly used range of 0.33 to 0.5 PGA.

The present paper investigated the dynamic and durability characteristics of silty-sand soil used in the base layer treated with cement and a mineral polymer via a series of laboratory tests.The specimen selection for the cyclic triaxial test was based on the results of the uniaxial compressive strength, Brazilian tensile, wetting-drying and freezing-thawing cycles tests. The results showed that, the compressive strength of the cemented soil can be reached in the shorter period of times and volume loss of the cement specimen may be eliminated due to the use of polymer. The compressive strength of the treated specimen with 6.3% cement and 0.7% polymer and has been selected as the optimal combination. In the durability test, the cement-polymer specimens show a better performance than cement specimens, and this trend is more noticeable in wetting-drying cycles than freezing-thawing cycles. In the next step, the cyclic triaxial test was performed on four optimal combinations with treated cement and cement-polymer. An increase in frequency raises the resileient modulus and damping ratio, while it has decreased the axial strain. For AASHTO T307 stress level, the mean values of the resilient modulus of cement-polymer specimen were higher than cement specimen in two curing modes. Meanwhile, for damping ratio parameter, the cement specimen show a better performance than cement-polymer specimen. Generally, soil treatment with the cement-polymer specimen demonstrated a relative advantage over the cement-only specimen in the medium stress range for the base layer in wetting-drying mode (as defined by stress levels in AASHTO T307 standard).

In this study, the effect of the unreinforced and geogrid-reinforced granular blankets, end-bearing stone columns and the combination of these techniques on the behaviour of loose sand soil models have been investigated through laboratory and numerical simulations. In the models, a stone column from a large group of them with a triangular pattern was simulated in a unit cell. Since the rupture of the geosynthetic reinforcement within the reinforced granular blanket has never been experimentally investigated, a novel method of installing the geogrid reinforcement was used, allowing it to mobilize and ultimately fail under loading. The optimal thickness of the unreinforced and geogrid-reinforced blanket, the optimum layout of the reinforcement within the blanket and the changes in the stress concentration ratio of the stone column in different modelling conditions have been determined. Another objective of the present study is to discover the relationship between the failure of the geogrid layers and the characteristics of load-carrying capacity and settlement of the model tests.

Recently, industrial development and high growth of constructions have increased the need to pay attention to the improvement of construction sites. Meanwhile, soil biological improvement as a new, low cost and environmentally friendly method has been considered by many researchers. On the other hand, the use of micro piles by cement or chemical grout injection as one of the methods of soil improvement has been proposed since almost the middle of the twentieth century. Of course, one of the disadvantages of micro piles is the use of cement or chemical grouts, which have both limited resources and environmental pollution. The use of biological micro piles is one of the new and economical solutions to solve these problems.

Soil nailing is one of the common methods used to stabilize excavation walls. This technique has been in attention in recent years. A variety of studies have been performed to optimize the pattern, length and inclination of nails in the design of soil nailing. The nail inclination has been one of significant optimization variables considered in previous studies. As a constraint of the optimization process, it has been assumed in previous studies that the inclinations of all nails through the depth of a soil-nailed wall must be equal. On the contrary, the present study presumes that the inclination of each row of nails could be different; in other words, the inclination of each row of nails is an independent optimization variable. The present study takes into account two approaches to optimize the design of soil nailing. In the first approach, the ratio of the maximum length of nails to the wall height is unconstrained but in the second approach, it is limited to the ratio proposed by the FHWA manual. The results of the present study show that two optimization approaches lead to different optimized inclinations for nails. For the first approach, the optimized inclination of all rows of nails equal to be 5 degree with respect to the horizon but in the second approach, these inclinations are different for rows of nails in the way that they reduce from the top row to the bottom one.

Deep excavations in urban areas require not only the stability of retained soil, but also special attentions due to the buildings existing nearby. They must be designed in such a way that the requirements for both ultimate and serviceability limit state for supporting system and neighbouring structures are satisfied. Anchored diaphragm walls are one of the safest lateral supports which help in overall stability of excavated areas. Diaphragm walls represent in general a considerably more complex problem than gravity or cantilever walls. Methodology and Approaches: The wall displacement, maximum bending moment and anchor extreme force were calculated using a dynamic PLAXIS finite element program. The soil was considered as elasto-plastic material, using Mohr–Coulomb constitutive model. The wall and the anchor were considered to behave elastically. Considering the dynamic applied load, absorbent boundaries were assumed to prevent dynamic wave reflection. Three different historical strong motions namely, Tabas, Bam and Roodbar were applied to the wall. The above mentioned outputs were obtained for different excavation geometry and mechanical properties for soil. Results and Conclusions: general results can be drawn as following:1-Change in the soil stiffness (modulus of elasticity and cohesion) from soft to stiff has caused the maximum wall displacement and bending moment increase by 76% and 20%, respectively.
2- Under dynamic load the maximum lateral displacement of the wall is at its top, while the static wall displacement is maximum at about one third the wall height measured from its toe.
3-Peak ground acceleration has direct effect on maximum wall displacement and bending moment, while earthquake frequency has inversely changes these output parameters. Based on obtained results 30% increase in earthquake acceleration has caused the maximum wall displacement increase by 15%
4- The maximum displacement and bending moments increased noticeably under earthquake load. So, for diaphragm walls in earthquake prone area, dynamic case should be considered in design. Albeit, building codes, accept higher displacement and bending moments under exceptional loading's.

Recently, public places and underground transport facilities such as subways and urban transport tunnels and routes have been targets of terrorists. Twin tunnels are built because of their structural strength and ease of construction. In this study, the behavior of tunnels with different cross-sectional geometries was examined numerically by FLAC under the impact of explosive forces. The results suggested that the performance of tunnels with a horseshoe section performance will be better than rectangular. In recent decades, there have been reports about explosion in tunnels. In this article, the performance of twin tunnels with three different shapes under internal explosion was studied. Consequently, horse-shoe tunnels have better performance. Stevens et.al. have studied the impact of surface explosions on tunnels in different conditions. Ghaemi explained the effect of emission of missile compressive waves and their impact in continuous and discontinuous environment. Liu presented the nonlinear response of tunnels buried under explosive loading. Lee studied the stability of a tunnel which was adjacent an exploded tunnel. Tian studied the dynamic response of multi-story buildings affected by explosion in one of two twin tunnels. In the previous studies, the effect of cross-sectional shape of twin tunnels has not been investigated. The shapes of twin tunnels were adopted according to code 161 of ministry of road and urban development. Four types of twin tunnels were considered. The primary section is the combination of 2 circles with 12.5 and 5.8 meter radii for each tunnel. The first suggested section is a rectangle with 10m width and 6m height for each tunnel. The second section is a circle with 12.5 radius and a line with 10 meter length for each tunnel. The third section is the combination of 3 circles with 12.5, 6.4 and 2.9 meter radii for each tunnel. FLAC was applied. Mohr-Coulomb failure criteria was used for soil.
Results and Bending moments and axial force in the crown of the damaged tunnel and adjacent tunnel were obtained for four different cross-sectional shapes. The results showed that the stress caused by the detonation was much lower than the compressive strength of concrete, while bending moments are high. Therefore, when an explosion occurs, rectangular tunnels have poorer performance compared to other types of the horseshoe tunnel. Among the tunnels with horseshoe section, the second section shows a good performance against explosion.

Detonation of explosives in saturated sandy soils generates high-intensity compressive stress waves. These stress waves cause a significant increase in pore water pressure and a decrease in effective stress that may cause soil liquefaction. Therefore, understanding the mechanism of explosion-induced soil liquefaction development and how to decrease its damages can be vitally important for geotechnical and passive defense engineers. Because of the complex structure of soil, high amplitude blast loading, short time of detonation, high strain and pore water pressure, the numerical modeling of explosion-induced liquefaction is very complicated. Moreover, experimental results are highly dependant on the site condition and methods of experiment. In this paper, an explosion-induced soil liquefaction phenomenon has been simulated in three-dimensional space using LS-DYNA V971 R4.2 explicit dynamic nonlinear finite-element analysis code. To model soil properties in these analyses, MAT-FHWA-SOIL saturated sandy soil has been used which is available in LS-DYNA code with the modified Mohr-Coulomb behavior. To apply blast loading, a buried cylindrical explosive charge located on the axis of symmetry of the model has been used. The JWL equation of state has been applied to simulate blast phenomenon. In addition to numerical modeling of explosion-induced soil liquefaction phenomenon, parametric studies have been conducted for the investigation of effects of parameters in relation to soil properties and loading conditions on the generation of residual excess pore water pressure. The obtained results from this research demonstrate that increasing the skeleton bulk modulus of the soil leads to the increasing residual excess pore water pressure. Soil parameters, such as cohesion, maximum, and residual internal friction angle, are the factors that have no effect on the generation of residual excess pore water pressure.

Expansive soils are generally found in many parts of the world, especially in arid and semi-arid areas. Because of the ability of volumetric changes in response to seasonal fluctuations of moisture content, these soils are known as a harmful phenomenon in geotechnical engineering. Such soils swell when the moisture content is increased and shrink when the moisture content is decreased. Consequently, expansive soils cause detrimental damage to the structures founded on them. Clay soil can be stabilized by the addition of small percentages, by weight, of lime, thereby enhancing many of the engineering properties of the soil and producing an improved construction material.In this study, in order to find an optimum percentage of the lime to stabilization of expansive soil, the expansive soil was stabilized with various amounts of dolomite quick lime. Next, in order to find the effective type of lime to reduce the swelling potential, the expansive soil was stabilized with two types of lime such as Dolomite lime and Calcite lime that are used as quick lime and hydrated lime. Finally, in the last step, the soil was stabilized with lime by different methods to find the best method of adding lime to the soil.The results show that the optimum percentage of adding lime is 3% of the total weight of expansive soil. However, the results indicate that the use of calcite quick lime shows a lower free swell, but a higher swelling pressure than the use of dolomite quick lime. It is also expressed that stabilization of expansive soils with hydrated lime has higher free swell and lower swelling pressure, in comparison to the stabilization with quick lime. The experimental results also show that adding lime in the optimum moisture of soil is the most effective method of stabilization of expansive soil.

A‌l‌l s‌t‌r‌u‌c‌t‌u‌r‌e‌s a‌r‌e b‌u‌i‌l‌t o‌n f‌o‌u‌n‌d‌a‌t‌i‌o‌n‌s w‌h‌i‌c‌h a‌r‌e u‌s‌e‌d t‌o t‌r‌a‌n‌s‌f‌e‌r l‌o‌a‌d‌s f‌r‌o‌m s‌t‌r‌u‌c‌t‌u‌r‌e‌s t‌o t‌h‌e b‌e‌a‌r‌i‌n‌g s‌t‌r‌a‌t‌u‌m. I‌n c‌e‌r‌t‌a‌i‌n c‌a‌s‌e‌s, w‌h‌e‌r‌e s‌h‌a‌l‌l‌o‌w f‌o‌u‌n‌d‌a‌t‌i‌o‌n‌s a‌r‌e n‌o‌t s‌u‌i‌t‌a‌b‌l‌e f‌o‌r t‌r‌a‌n‌s‌f‌e‌r‌r‌i‌n‌g l‌o‌a‌d‌s, d‌e‌e‌p f‌o‌u‌n‌d‌a‌t‌i‌o‌n‌s s‌u‌c‌h a‌s p‌i‌l‌e f‌o‌u‌n‌d‌a‌t‌i‌o‌n‌s a‌r‌e u‌s‌e‌d. I‌t i‌s w‌o‌r‌t‌h m‌e‌n‌t‌i‌o‌n‌i‌n‌g t‌h‌a‌t i‌n m‌o‌s‌t c‌a‌s‌e‌s, c‌y‌l‌i‌n‌d‌r‌i‌c‌a‌l p‌i‌l‌e‌s h‌a‌v‌e b‌e‌e‌n u‌s‌e‌d. H‌o‌w‌e‌v‌e‌r, p‌a‌s‌t r‌e‌s‌e‌a‌r‌c‌h r‌e‌v‌e‌a‌l‌e‌d t‌h‌a‌t t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y a‌n‌d s‌t‌i‌f‌f‌n‌e‌s‌s o‌f t‌a‌p‌e‌r‌e‌d p‌i‌l‌e‌s a‌r‌e m‌o‌r‌e t‌h‌a‌n t‌h‌e‌i‌r c‌y‌l‌i‌n‌d‌r‌i‌c‌a‌l e‌q‌u‌i‌v‌a‌l‌e‌n‌t‌s.T‌h‌e‌r‌e h‌a‌s b‌e‌e‌n l‌i‌m‌i‌t‌e‌d e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌a‌l r‌e‌s‌e‌a‌r‌c‌h c‌a‌r‌r‌i‌e‌d o‌u‌t o‌n t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f t‌a‌p‌e‌r‌e‌d p‌i‌l‌e‌s, a‌n‌d m‌o‌s‌t s‌t‌u‌d‌i‌e‌s i‌n t‌h‌i‌s a‌r‌e‌a a‌r‌e b‌a‌s‌e‌d o‌n n‌u‌m‌e‌r‌i‌c‌a‌l a‌n‌a‌l‌y‌s‌i‌s. R‌e‌s‌u‌l‌t‌s o‌f t‌h‌e a‌b‌o‌v‌e m‌e‌n‌t‌i‌o‌n‌e‌d r‌e‌s‌e‌a‌r‌c‌h i‌n‌d‌i‌c‌a‌t‌e t‌h‌a‌t t‌h‌e‌r‌e i‌s a re‌l‌a‌t‌i‌o‌n‌s‌h‌i‌p b‌e‌t‌w‌e‌e‌n t‌h‌e t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e a‌n‌d t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f t‌h‌e p‌i‌l‌e‌s. I‌n t‌h‌i‌s s‌t‌u‌d‌y, t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y a‌n‌d s‌e‌t‌t‌l‌e‌m‌e‌n‌t o‌f t‌a‌p‌e‌r‌e‌d p‌i‌l‌e‌s u‌s‌i‌n‌g d‌i‌f‌f‌e‌r‌e‌n‌t t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e‌s h‌a‌v‌e b‌e‌e‌n s‌t‌u‌d‌i‌e‌d. F‌o‌u‌r d‌i‌f‌f‌e‌r‌e‌n‌t t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e p‌i‌l‌e‌s w‌e‌r‌e i‌n‌s‌t‌a‌l‌l‌e‌d i‌n t‌w‌o d‌i‌f‌f‌e‌r‌e‌n‌t s‌o‌i‌l‌s, n‌a‌m‌e‌l‌y; f‌i‌n‌e g‌r‌a‌i‌n s‌a‌n‌d (r‌e‌g‌i‌o‌n‌a‌l‌l‌y n‌a‌m‌e‌d Y‌a‌z‌d W‌i‌n‌d‌y S‌a‌n‌d), a‌n‌d a f‌a‌b‌r‌i‌c‌a‌t‌e‌d c‌o‌a‌r‌s‌e a‌n‌g‌u‌l‌a‌r s‌a‌n‌d. U‌s‌i‌n‌g a l‌o‌a‌d c‌e‌l‌l a‌t t‌h‌e t‌i‌p o‌f t‌h‌e p‌i‌l‌e, t‌h‌e t‌r‌a‌n‌s‌m‌i‌t‌t‌e‌d l‌o‌a‌d t‌o t‌h‌e p‌i‌l‌e b‌a‌s‌e h‌a‌s b‌e‌e‌n m‌e‌a‌s‌u‌r‌e‌d a‌n‌d t‌h‌e l‌o‌a‌d t‌r‌a‌n‌s‌f‌e‌r‌r‌e‌d b‌y s‌k‌i‌n f‌r‌i‌c‌t‌i‌o‌n c‌a‌l‌c‌u‌l‌a‌t‌e‌d b‌y s‌u‌b‌t‌r‌a‌c‌t‌i‌n‌g t‌h‌e b‌a‌s‌e l‌o‌a‌d f‌r‌o‌m t‌h‌e w‌h‌o‌l‌e a‌p‌p‌l‌i‌e‌d l‌o‌a‌d. T‌h‌e r‌e‌s‌u‌l‌t‌s d‌e‌m‌o‌n‌s‌t‌r‌a‌t‌e‌d a r‌e‌l‌a‌t‌i‌o‌n‌s‌h‌i‌p b‌e‌t‌w‌e‌e‌n t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e a‌n‌d b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y, w‌h‌i‌c‌h h‌a‌v‌e b‌e‌e‌n c‌o‌m‌p‌a‌r‌e‌d w‌i‌t‌h t‌h‌e‌i‌r c‌y‌l‌i‌n‌d‌r‌i‌c‌a‌l e‌q‌u‌i‌v‌a‌l‌e‌n‌t‌s. A‌v‌a‌i‌l‌a‌b‌l‌e r‌e‌c‌o‌m‌m‌e‌n‌d‌e‌d m‌e‌t‌h‌o‌d‌s h‌a‌v‌e b‌e‌e‌n u‌s‌e‌d t‌o d‌e‌d‌u‌c‌e t‌h‌e u‌l‌t‌i‌m‌a‌t‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f p‌i‌l‌e‌s f‌r‌o‌m l‌o‌a‌d- s‌e‌t‌t‌l‌e‌m‌e‌n‌t c‌u‌r‌v‌e‌s. B‌a‌s‌e‌d o‌n a‌c‌q‌u‌i‌r‌e‌d r‌e‌s‌u‌l‌t‌s, p‌i‌l‌e‌s w‌i‌t‌h a 2.45 d‌e‌g‌r‌e‌e o‌f t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e i‌n f‌a‌b‌r‌i‌c‌a‌t‌e‌d c‌o‌a‌r‌s‌e a‌n‌g‌u‌l‌a‌r s‌a‌n‌d h‌a‌v‌e t‌h‌e m‌a‌x‌i‌m‌u‌m b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y. F‌u‌r‌t‌h‌e‌r‌m‌o‌r‌e, i‌n f‌i‌n‌e s‌a‌n‌d, t‌h‌e u‌l‌t‌i‌m‌a‌t‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y r‌e‌d‌u‌c‌e‌s w‌i‌t‌h t‌a‌p‌e‌r‌e‌d a‌n‌g‌l‌e a‌f‌t‌e‌r a‌n o‌p‌t‌i‌m‌i‌z‌e‌d a‌n‌g‌l‌e.

Ardakan is located in Iran’s central desert. Cracking has caused significant damage to buildings and arteries in this region. Different theories have been associated with the explanation of these cracks, the strongest of which is the problematic soils (expansive soils, dispersive soils and collapsible soils). In this respect several geotechnical tests performed on five bores up to 14 meters in depth. To determine the swelling potential of soil, direct (standard A methods of ASTM D4546) and indirect (various criteria including Chen, AASHTO, Kaldveer, Vander Merwe and free swell test) methods were used.
It was concluded that soils have moderate swelling potential. This feature in some cases can cause cracks in the structures. It has also been concluded that the dispersion and collapse potential of soil are negligible.