1718 ENGLAND AVE 2016-01-01 MF Import

IGcotcchnical Enginecring Evaluation England Avenuc Lot � June 2, 2005 NGA Fiic No.411805 � Page 11 uphill side of the swcwre. The lateral pressure acting on subsurfacc retaining wzlls is depcndent on the II nature and densiry of the soil behind the wall, the amount of lateral wall movement which can occur as � backfill is placcd, wall dr�i��ge conditions, and ihc inclination of thc backfill. For walls that arc frcc to yield at the top at least one thousandth of the height o(the wall (active condition), soi! pressures will tx� ( less than if movement is limited by such factors as wall stiffness or br.icing (at-rest condition). Wc I recommend Qiat walls supporting horizonlal backfill and not subjected to hydrostatic forces be desigm d I using a triangular earth pressure distribution equivalent to that exerted by a Fluid wiih :� dcnsity of 35 pcf for yieldino(active conJition) walls, and 55 pcf for non-yielding(at-rest condition) �valls. lThese rccommended laterd eartl� pressures are for a dmined backfill and are based ou thc assumption of a horizontal ground surface behind the wall for a distance of at Icast the subsurface height of the wall, anJ Ido not accowu for surch.�rgc loads. Addition,d latcral carth pressurcs shoulJ bc considercd for surch::,gc IoaJs ucting adjacent to subsurface walls and within a dis�cince equal to the subsurface height of the ��;�II. IThis would include the effects of surcharges such as Iraffic loads, Floor slab loads, slopes, or other surfxc IoaJs. Wc could consult with you and your stnictural cn�,inccr rc��arding additional loads on rctainine ( walls and dcbris walls during final design, if necdcd. IThe lateral prcssures on walls may be resisted by friction bct��e�n the found:uion anJ subgrade soil, ,md by p;�ssive resishuice acting on the below-grade portion of the foundation. Recommendations for � friction;d �md p;issi�c rcsist,mcc to lalcril lo,ids ,irc pr�scntcd in thc Foundations subsection of this � repurt. All w:dl b:ickfill should bc wcll compac�cd :�s uutlincd in thc Structural Fill subscction oF this report. I Care should be taken lo prevent the buildup of c�cess lateral soil pressures,duc to overvcompaction of the � wall backfill. This can be accomplished by placing wall backfill in six-inch loose lif'ts nnd compactina it with small, hand-operated compactors within a distance behind the wall equal to at least one-half the Ihcight of the wall. The thickness of the loose IiRs should be lessened to accommodate the lower compactive energy of the hand-operated equiproent. The recommended Ievel of compaction should still Ibc maintaincd. Ne are av:�ilable to provide specific rctainim� �eall/,horing recommendations as the �rojcct plans Jc�'clop. I � NELSON GEOTECHN/CAL ASSOCIATES, INC. I