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60 For large loads and/or poor soil conditions, a concrete pad should be placed in the bottom of the hole. This increases the bearing area and capacity as shown in Figure 7.2. For very poor soil, it may be necessary to use a group of piles and a pile cap to support each post as shown in Figure 7,3, Possible backfill material includes sand, gravel, crushed rock, soil cement, concrete, and earth. Soil cement can attain strength nearly equal to concrete and is made by mixing earth with cement in a 5:1 ratio (earth:cement). All organic matter should be removed from the soil prior to mixing. If an earthen fill is used, it should provide good drainage away from the posts or piles so that deterioration is minimized. By anchoring the posts, more resistance to overturning and uplift will be provided. A properly designed pile support will have sufficient frictional capacity such that added anchoring is not needed, Posts may be anchored by either embedding them in concrete or fastening them to metal pieces which are embedded in concrete, Two methods are shown here (Figure 7.4). In either case, posts must be braced until the concrete sets. WOOD POLE i !~ ..L Ii GRADE~ ' II 'lY__- - Uk lL Lt~-oL - ,...~''''''r....... ~~~~ l j --'- r-, I '-'I ,'i I....... :"\ ,;'<11' I : --,-'1 ~'/,' 'SPIKES OR i 'y' : LAG SCREWS I _J.. I \" CP"(.I) ,J ........... i "" ......, I ,;' .......l..,...... WOOD POST ....:1...--- .l. GRADE~ _'>L 3.:~i.1JL--\'-- ~/II'I;:I~ i-- _ GALVANIZED STRAP ... 'II ...>. {..... .,.......(1 ....' I I......... 1111...... : I ........' j..l.-' I I I "" I -+- FOOTING I /'.JI'..P I I ~..... , ) '- I , ...... I ...'" ...... I "" ........ I ...' ,v Figure 7.4. Posts anchored to concrete, (Reference 7) If a post or pile system is incapable of resisting the expected lateral loads on their own, permanent bracmg must be added, Two of the several methods are pictured here, The knee brace (Figure 7.5) is 2" by 6" lumber nailed or bolted between the floor joist and post or pile. Cross bracing is similar but extends from the top of one post or pile to the bottom of the adjacent one. Figure 7,6 shows cross bracing with the use of threaded rods, Such bracing should be in a plane parallel with the flood flow for the least obstruction, least potential for trapping debris, and most efficient use of material.