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EM 1110.2.2504 31 Mar 94 I. x _ I. c .1. b -I N o =..9.. {- !.a+ c+b-x II H II C b 2z R2 2z R2} +-In-+-In- c R1 b ~ Figure 4-8. Triangular load e. Triangular loads. A lriangular load varies per- pendicular 10 Ihe wall as shown in Figure 4-8 and is assumed 10 be continuous parallel 10 Ihe wall. The equation for IaleraI pressure is given in Figure 4-8. f Area loads. A SlD'Charge dislribuled over a Iim- iled area. both parallel and petpendicular 10 Ihe wall, should be treated as an area load. The IaleraI pressures induced by area loads may be calculated using New- mark's Influence CharIs (Newmarli: 1942). The IaleraI pressures due 10 area loads vIII)' wilh deplh below Ihe ground surface and wilh horizonlal distance parallel 10 Ihe wall. Because the design procedures discussed subsequendy are based on a typical unil slice of the wall/soil syslem. il may be necessary 10 consider several slices in Ihe vicinily of the area load. g. Point loads. A surcharge load distribuled over a small area may be treaIed as a point load. Ihe equations for evaluating IaIeraJ pressures are given in Figure 4-9. Because the pressures vIII)' horizonlalJy parallel 10 Ihe wall; il may be necessary 10 consider several unil slices of the wall/soil syslem for design. 4-5. Water Loads a. HydroslIllic prtSSlUt. A difference in water level on either side of the wall creates an unbalanced hydro- static pressure. Waler pressures are calculaled by multiplying Ihe waler deplh by ils specific weight. If a nooflow hydrosla1ic condition is assumed, i.e. seepage 4-6 effecls negJecled, Ihe unbalanced hydrostatic pressure is assumed 10 acl along Ihe entire deplh of embedment. . Waler pressure must be added 10 Ihe effective soil pres- '. sures 10 oblain IoIaI pressures. b. Seepage effects. Where seepage occurs, Ihe dif- ferential waler pressure is dissipaled by vertical flow beneath Ihe sheeI pile wall. This distribution of Ihe unbalanced waler pressure can be oblained from a seepage analysis. The analysis should consider Ihe penneabilily of Ihe slUTOUnding soils as well as Ihe effectiveness of any drains if presenL Techniques of seepage analysis applicable 10 sheel pile wall design include flow nels, line of creep melhod, and method of fragmenls. These simplified techniques mayor may not yield conservative resulls. Therefore, il is Ihe designer's responsibilily 10 decide whether Ihe final design should be based on a more rigorous analysis, such as Ihe finile elemenl melhod. Upward seepage in fronl of Ihe sheel pile wall lends 10 reduce Ihe effective weight of Ihe soil. Ihus reducing ils abilily 10 offer Ialeral support. In previous maleriaI Ihe effecls of upward seepage can cause piping of maleriaI away from the wall or, in exlreme cases, cause the soil 10 liquefy. Lenglhening Ihe sheet pile, Ihus increasing Ihe seepage paIh, is one effective melhod of accommodating seepage. For sheel pile walls thai relain backfill, a drainage colleclor sys- tem is recommended, Some methods of seepage analy- sis are discussed in EM 1110-2-1901. e) c . Wave action. The laleral forces produced by wave action are dependenl on many faclors, such as lenglh, heigh!, breaking poin!, frequency and deplh at struclure, Wave forces for a range of possible waler levels should be delermined in accordance wilh Ihe U,S. Anny CoasIaI Engineering Research Cenler Shore ProIection Manual (USAEWES 1984). 4-6. Additional Applied Loads Sheet Pile walls are widely used in many applications and can be subjected to a number of additional loads, other Ihan Ialeral pressure exerted by soil and waler, a. Boat impact, Allhough it becomes impractical 10 design a sheet pile wall for impacl by large vessels, waafronl stnJclures can be struck by loose barges or smaller vessels propelled by winds or cwrenls. Con- struction of a submerged berm thai would ground a vessel will greatly reduce lhis possibilily of impacL When the sheet pile structure is subject 10 docking impact, a fender system should be provided 10 absorb e)