Banks

FIGURE 3-2. Approaches - link reinforced MGB

TM-5-5420-212-10-1 Improved Flaot Bridge Consisting of: Transporter Interior Bay Ramp Bay Manual
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ARMY TM 5-5420-212-10-1 MARINE CORPS TM 08676A-10/1-1 c. Banks (1) Single and Double Story MGB Firm and stable banks of about equal height. The difference in bank height cannot exceed 10% of the bridge length, as the bridge is restricted to a 1 in 10 slope. (2) Link Reinforced MGB Firm and stable banks of about equal height. The difference in bank height cannot exceed 5% of the bridge length, as the bridge is restricted to a 1 in 20 slope (3) Banks at expected bearing points of bridge should have a Soil Bearing Capacity (SBC) of 2 tons per square foot. Table 3-3 lists SBC of various types of soil. TABLE 3-3 Soil bearing capacity Soil Description Bearing values in tons per square foot Hardpan overlaying rock 12 Very compact sandy gravel 10 Loose gravel and sandy gravel, compact sand and gravelly sand; very compact sand- inorganic silt soils 6 Hard dry consolidated clay 5 Loose course to medium sand, medium compact fine sand 4 Compact sand clay 3 Loose fine sand, medium compact sand-inorganic silt soils 2 Firm or stiff clay 1.5* Loose saturated sand-clay soils, medium soft clay 1* *Bridges constructed on this type of soil will require packing to cover a 3 ft (0.9 m) area under ETP to spread weight of bridge. Watch settling during crossing of traffic, and increase packing if needed. Packing material required is 3 in x 8 in x 36 in lumber, and the height of packing will be the minimum necessary to keep ETP’s from touching bank. d. Size of Construction Site (1) Types of Sites (a) Normal - provides construction space that allows fast and easy construction. (b) Restricted - construction space is limited, and requires special construction procedures e.g. longer launching nose, counterweights and more frequent booming of the bridge. (2) Assembly Site Assembly site large enough for assembly of the bridge and wide enough for unloading and positioning of the loaded bridge pallets. The desired size of the assembly site for the longest single story bridge is 160 ft wide x 80 ft long (48.8 m x 24.4 m). The desired size for double story and link reinforced bridges is 160ft wide x 160 ft long (48.8 m x 48.8 m). 3-11

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