Deep excavations are frequently carried out near structural foundations in densely populated metropolitan areas. Those foundations surrounding the excavation site can impose additional lateral pressure on the retaining wall along with backfill pressure. A three-dimensional finite element analysis has been performed in the present study to determine the effect of square and circular footings of the same plan area on the sheet pile wall behaviour. A parametric study is performed by varying the plan area of footing, embedded depth of sheet pile, magnitude of surcharge loads, position of footing above and below the backfill surface from the top edge of the wall, the depth of the loose soil layer, and dredge line slope angle to find out the wall deflection, bending moment, and backfill ground settlement. The results show that the effect of square and circular footing highly influences the wall and backfill soil. However, the effect of square footing on the wall and backfill soil is more substantial than that of circular footing for the same plan area.

Due to the widespread problem of excavation in urban and non-urban constructions, the importance of stabilization of excavations and walls is felt more. One of the methods used in this matter is the use of steel sheet pile walls. When using steel sheet pile wall, the soil in and around the site may be of weak soil type for backfill, so it is necessary to strengthen this soil by using different methods. In this research, using the available information about the characteristics of the mixture of sandy soil and tire chips with volume ratios of 15 and 30%, the behavior of the sheet pile wall with different heights, under the effects of increasing the depth of the reinforced layer in the backfill, with The use of PLAXIS finite element software is investigated. The results show that the use of a mixture of sand and tire chips in the backfill part of the wall instead of full sand backfill leads to a reduction in the lateral displacement and the bending moment of the sheet pile. Also, the anchor force decreases. In this case, the settlement, increases to a small amount. Also, by increasing the depth of the reinforced layer, so that the entire backfill is reinforced with tire chips, the lateral displacement and bending moment of the sheet pile is reduced.

The seismic performance of quay walls is found to be strongly dependent on liquefaction occurrence. Besides, in some existing walls that were designed without consideration of the liquefaction hazard, due to the relatively long length of quay walls, the orientation of soil strata probably caused the liquefiable layers to appear unavoidably neighboring the wall roots. In this paper, the dynamic response of anchored sheet pile quay walls embedded in liquefaction susceptible soil was investigated numerically, utilizing the strain space plasticity model for cyclic mobility available in the DIANA finite element program. Based on the results, the extension of liquefiable soil around the wall root leads to the "failure at embedment" mode. Deformed mesh indicates that the most visible deformations are localized in loose soil around the embedded section. Beside the noticeable heave of the seabed, its seaward displacement causes a significant reduction in its supporting role for the embedded section, and leads to the large tilt of the wall. Consequently, an active wedge, extending from the embedded section to the back of the anchors, is formed. Moving along this wedge, the anchors endure significant overturning. The mentioned deformation shape was previously observed in shaking table tests conducted by the authors. The leeward section of the loose layer is recognized as the most vulnerable zone against liquefaction. Besides the effect of soil softening in this zone, dynamic active pressure behind the wall causes the bottom of the wall to experience higher displacement than its top. The time history of monotonic bending moment infers that considerable moment is applied to the wall root by the loose section behind the root. This moment is the main reason for the "escape" of the wall root. The remediation method, by deep vibro-compaction of the weak area, is considered as a liquefaction countermeasure. The effectiveness of soil improvement in zones adjacent to the embedded section is discussed, based on analytical dynamic responses. Implemented countermeasures are found to considerably reduce deformations in the wall; however, in order to prevent failure at embedment, improvement of soil located behind the wall root is more effectual. The compacting of this section not only reduces driving moment applied to the wall root, but also creates resistant moment against root escaping. In addition to the impact of base acceleration amplitude, the optimum extension of improved zones is introduced.

Steel sheet pile walls are being widely used as earth retaining systems. Sometimes loose or soft soil layers are located in various depths in an excavation. This issue causes different effects on ground surface displacements, forces and moments acting on sheet piles and struts during excavation procedure, compared with a status that soil is totally uniform. These differences are not exactly considered in conventional design methods of sheet pile walls. In this paper, a deep excavation using finite element method is analyzed. Excavation’ s depth is divided into three different layers. One of three layers is a loose soil layer and its position is modeled in three different situations, top, middle and bottom of the model. Obtained results are compared with results of excavation without the loose layer. The pseudo-static analysis is performed by applying 0. 3g horizontal acceleration. The results indicate that when a loose layer is located beneath stiffer layers, bending moments acting on sheet pile wall and shear forces increase about (50~100)% and (15~50)%, respectively. Also, the middle loose layer changes the location of maximum lateral deformation of steel sheet pile wall.

Conventional methods used for the design of sheet pile walls as a retaining system are based on the lateral force equilibrium and proposed equations. Soil is not uniform in depth, sometimes, soft soil layer may exist in various depth and situations. This issue can cause different effects on forces and moments acting on sheet pile and struts during the excavation procedure, compared with status such that soil is uniform in depth. In this study, a deep excavation using the finite element method is analyzed. Excavation's depth is divided into three clayey layers. One of the three layers is soft clay layer whose position ns are modelled in three different situations, top, middle, and bottom. The obtained results are compared with those of the conventional design method. According to the comparative obtained results, it can be concluded that: 1. In relatively uniform soil deposits, conventional methods cannot correctly estimate sheet piles maximum bending moment locations. 2. In status in which a soft clay layer exists between two stiff clay layers whose thicknesses of all three layers are the same, bending moment location acting on sheet pile is different from other status and is very close to the conventional method value. 3. By increasing the depth of soft clay layer, bending moments acting on sheet piles are increased, especially in the final stages of excavation. This issue is not considered in the conventional method. 4. When the soft clay layer is a surface layer whose thickness does not exceed the one-third the depth of the excavation, using the conventional method for design practices is conservative. 5. It appears that the conventional method underestimates the forces of struts near excavation depth so that, in the current study, forces of these struts are increased by about 15-70 % in finite element method in comparison with conventional method. Using equivalent cohesion and specific gravity in layered soils cannot consider location effects of different soil layers.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradient at the ‎outlet of such structures rested on permeable foundations.‎‏ ‏So far, for analysis of seepage under hydraulic ‎structures much research work has been conducted in the form of numerical models. However, less field and ‎laboratory works have been done to study boiling phenomena for evaluating of the numerical models. In the ‎present research work, a laboratory model was made to simulate seepage and its controlling measures under ‎coastal dikes. The model consist of a flume 2.2 m long, 0.8 m deep and 0.4 m wide, in which vertical sheet pile ‎were provided by Perspex sheets. The flume was made of steel frame and Perspex as well as thick glass ‎sheets. The foundation material was made of clean, fine sand, compacted to a uniform density and covered ‎the bottom 40cm of flume. Perspex sheets were employed sheet pile variable depth. The piezometric heads at ‎the both downstream and upstream side of dike were measured using small diameter clear plastic tubes. The ‎effect of position and depth of the sheet pile on the seepage flow and exit gradient have been demonstrated in ‎form of dimensionless curves. The results show that the depth of the sheet piles d/D=0.46 with the maximum ‎upstream water level h/hm=1.0 boiling phenomenon does not occur and the seepage rate and hydraulic ‎gradient in the area are favorable.‎

So far, for an analysis of seepage under hydraulic structures much research has been conducted in the form of numerical models. However, few field and laboratory works have been performed to study the boiling phenomena for evaluating numerical models. Throughout the present work, a laboratory model was built to simulate seepage and its controlling measures under sheet piles. The model consisted of a 2.2 m long, 0.8 m deep and 0.4 m wide flume, in which vertical sheet piles were provided by Perspex sheets. The flume was made up of a steel frame, Perspex as well as thick glass sheets. The effect of position and depth of the sheet pile on the seepage flow, exit gradient and uplift pressure have been demonstrated in the form of dimensionless curves. The results indicate that the ratios d/D=0.44 and d/D=0.34 with a maximum upstream water level of h/hm=1.0 form the best possible depths, for both vertical and inclined sheet piles in the depth of the foundation sheet pile. In other words, inclined sheet piles are much more effective in reducing and controlling seepage, uplift pressure and hydraulic gradient than the vertical ones.

Recent studies regarding dam failure show that most dam failures are due to unsuitable conditions of foundation and insufficiencies depth of bed rock. Seepage, uplift pressure and piping phenomenon under the foundation of dam cause disastrous failures in dams that exit gradient is an important criterion for safety against piping. Therefore, finding methods will be to reduce seepage flow, exit gradient and uplift pressure will be very important. In this study, ANSYS software is employed for analysis and modeling water flow in foundation dam. This study determines the flow characteristics (flow rate and exit gradient) and quantities of uplift pressure in an impervious dam with sheet pile. Extensive analyses were performed for different condition, including dam width and sheet pile depth. The results have been presented in simple charts. These simple charts allow designer to predict seepage problems and perform an optimum design in short time.