1901 MERRILL CREEK PKY 2018-01-01 MF Import

The recommended equivalent fluid density values also assume a free-draining condition behind the structure. This can be accomplished by placing a 2-foot-wide, full-height zone of sand and gravel containing less than 3 percent fines againct the rotaining stcucmre. A drainpipe should be installed at the base of retaining walls to remove any water in this zone of sand and gravel. �_ Weep holes may be adequate for external grade transition walls. � Retaining structure footings may be designed in accordance with our previous recommendations in the "Shallow Foundation" section af this report. � � Lateral loads can be resisted by friction along the baze oC ihe foundations and passive � tesistance along the sides of the foundations. Frictional resistance may be determined using a coe�cient of friction of 0.40 along the base of the foundations. Pusive resistance may be ` � deteRnined using an equivalent fluid density of 300 pcf for a Ievel backslope behind the wall. This passive resistance may be increased to 450 pcf if the adjacent soil consists of dense glacial till (extending out at least two and one-half tima the height of the foundation element). These values include a factor of safery of approximately 1.5. � Rockeries General. Rockeries may be use% m both cut and fill areas. In cut areas where dense �� native soils are ezposed, rockeries may be up to 10 feet high if the ground surface behind the a�all is level, or up to 6 fat high for a 1.SH:1V backslope. In structural fill areas, we � recammend limiting the wall height to 4 feet. If pazking will occur behind the rockery, we recommend that the fill be ninforced witii geoteztile or a diftbrent facing should be used. t,� We recommend that rockeries be founded on dense native soils or on structural fill ptaced to the recommended standazd. In our opinion, when adequate foundation support and suitable materials are present such as those outlined above, rockeries will provide the most cost-effective earth retention system. Specific construction guidelines for rockeries are presented in the foltowing paragraphs. Construction Guidelines. The primary purpose of a rockery is to protect the slope face ' from erosion and ravelling, while providing limited soil retention. The base of the rockery should be embedded at least one-half the thicknas of the lowest course of rocks or 18 incha below the adjacent ground surface, whichever is greater. 1'he rockery should be suppotted on firm,undisturbed native glacial till soils or on compacted st�uctutal fill. The final rock wall face should be constructed with a batter of between 5:1 and 6:1 (vertical to horizontal). The rockery rocks should be tabular and rectangular. Rocks shoutd be hard,sound,durable and free of weathercd poRions, seams, ctacks and other defects. Based on the height of the cut and the slope behind the rockery, we recommend that the rockeriu be consttucted using ra•k G e o E n ` i n e e r a IZ Ftle No. I460-006-77d 13011 t 1297 i