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� <br /> � <br /> Drain lines should be perforated or slotted PVC pipes at least 4 inches in diameter. The drain lines <br /> � should be encased in clean (less than 5 percent �nes passing #200 sieve) free-draining uniform <br /> granula�aggregate fuily wrapped in filter fabric to prevent soil from migrating into the drain tile over <br /> time. This soil migration may clog tt�e drain line or cause "piping" in adjacent soil surrounding the' <br /> � drain line (creation of a void space in the adjacent soil). <br /> LATERAL EARTH PRESSURE <br /> � Basement walls, retaining walls, and other walls that retain soil will be subjected to lateral earth <br /> pressure. Cohesive (lean clay) lateral earth pressures and parameters must be used in wall <br /> design when cohesive soil acts on walls. Granular soil (sand and gravel) lateral earth pressures <br /> I and parameters must be used in wall design when granular soil acts on walls. Estimated lateral <br /> eartfi pressures and parameters for cohesive and granular soils are given in TABLE L. <br /> ( TABLE L ESTIMATED LATERAL EARTH PRESSURES as EQUIVALENT FLUID PRESSURE �"� <br /> COHESIVE SOIL GRANULAR SOIL <br /> ' Approximate total density (pcfl � 130 ' 120 <br /> ------._------------_._.---�--._.-�--------.__--•--.._..--�----------------� � <br /> . - ----•---•-----•----•---�----•-----�;.._.._..-•--•---•------------.._..___.._.._._.._.._.._._. <br /> Approximate friction angle (deg) � 15—20 � 30—35 <br /> -�--------•----------•---------�----•--••----•--�._--•-----------:-----._.._..--•----�----�-.._..--•-------•---•---•--•-'------••----••--------------•-__.._------------•---- <br /> Active pressure coe�cient ke ' ' 0.3 <br /> ._._.___-------_.._..--�--•----__.._.-•---•-----------•�----------•---•---_._.._�-5•----••-------------•---•+---•---•-•.___._---._.._.._-------__�.._._------� <br /> At-rest pressure coefficient ko ; 0.7 ' 0.� <br /> ..------------•---•--------�-----•---•-----._.._.____.._.._.._.;_-•-----.._.._._..----•-----•--------•------•----��--•-••-•---•--•----------•_._.._---__..__._._.._.._. <br /> Passive pressure coefficient kP � 2 ' 3.3 <br /> ; ; <br /> Active Earth Pressure (pcfl <br /> •-------�-----�-------•--��--------•---__._�._.._..___..--•--r..-------••----•--••----•--�----.._.._.__.._..-••-�---•-----------------------•--•--.._.__._�_._.___._..__ <br /> Drained � � • <br /> --------------------- <br /> � 65 � 35 <br /> Undrained �}�-----•---------_.._.._.._..-_-••-----L..--•-•----------------•--•--•-•---------•-•�--------j---•---•-..-__._..__ 80__ ._.�__.--------- <br /> ' 95 , <br /> . At-Rest Earth Pressure (pc� <br /> ---•--�------•-�---•----------��--------------.._..�.--•----•---r---••-------�-----•-------•---------�-•---------••-•-�------••--�----•---._..__-•----••--.__._..------�-----• <br /> Drained ' 90 � ' <br /> -----=----•-----•----•- � . <br /> Undrained �} ._ .~--•--------------------------i.._.._.._.._.._..___..-110----••--•--------._..---;----•----.._..------------�9�.._.._.._..-------_.---_ <br /> � <br /> Passive Earth Pressure (pc� <br /> ----�----_..--•------------••----------•---•--•--•---•-------•r------•-----------•--•--•----------•------------._..----------------.._..-------•----•--..__.._-•-----------•--� <br /> Drained � . 260 � <br /> ..------------•------ 400 <br /> Undrained ��7---�--._.-------__._.._.-•_-----.�.--�-----•-----.._.._.-135_._..-------._.---_-�_-•---•-----_..----._.. 190�--------------••----•-- <br /> Notes: <br /> (A) Excludes cohesive shear strength sliding friction effeds <br /> (B) Combined factored soil buoyant unit weight and hydrostatic water head (62.4 pc� <br /> (C) Excludes hydrostatic water head (62.4 pcfl <br /> Active earth pressure design assumes the top of wall moves away from adjoining soil. Active earth <br /> pressures and parameters must be used in this case. Passive earth pressure design assumes the <br /> bottom of the wall moves toward adjoining soil. Passive earth pressures and parameters must be <br /> used in this case. If the top of the wall remains stationary, at-rest earth pressures and parameters <br /> must be considered in design. Increased lateral earth pressure can develop on walls due to poor <br /> or restricted soil water drainage, surcha�ge loads applied behind walls, over-compacting backfill <br /> Allied Project 05039 �g July 31, 2005 <br />