LENGTH OF DEADMAN

Figure 14. Determination of Deadman Dimensions.

TM-5-5420-278-10 M85 Tank Chassis Transporting: for Bridge Armored-Vehicle-Launched Scissoring Type Class 80 Manual
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TM 5-5420-278-10 0035 00 0035 00-22 BRIDGE ANCHORAGE (Contd) LENGTH OF DEADMAN Deadmen are designed to have lengths which enable them to resist the breaking strength of the cable attached to them. The required length and thickness are based on allowable soil bearing with 1 ft (0.3 m) of length added to compensate for the width of the cable trench. The formula for the determination of deadman length Dt is: Dt = CC + 1 (HP x Df) where CC is cable capacity (breaking strength) HP is the required holding power of the deadman. Df is the deadman face in feet (for log deadmen, use log diameter). This is the general formula for the determination of the required deadman length in all circumstances. In Appendix C of TC 5-210, the values for CC and HO have been divided by 1,000 for ease of calculation. Actual breaking strengths (CC) or cables were provided in table 7. The actual holding power of deadmen in loamy soil is provided in table 9. NOTE Table 9 assumes the deadman will be buried in loamy soil. For rock or hardpan soil, multiply the values in table 9 by a factor of 5. For fine-grained or sandy soil, multiply these values by a factor of 1/2. The tower-to-deadman slope used in table 9 represents an approximation of the slope of the cable running from the tower to the deadman, as shown in figure 16. Since this value cannot be accurately measured until the exact location of the deadman is known, an estimation is made. The tower-to-deadman slope should fall between a 1:1 slope (45 degrees) and a 1:4 slope (14 degrees). If it is not possible to obtain an accurate estimate, then assume the worst case (1:1) slope. REQUIRED HOLDING POWER (HP) IN LB/SQ FT DEPTH OF DEADMAN (DD) TOWER-TO-DEADMAN SLOPE 1:1 (45°) 1:2 (26.5°) 1:3 (18.5°) 1:4 (14°) 3 950 1,300 1,450 1,500 4 1,750 2,200 2,600 2,700 5 2,800 3,600 4,000 4,100 6 3,800 5,100 5,800 6,000 7 5,100 7000 8,000 8,400 Notes: 1. For hardpan or rock, multiply the HP by 5. 2. For fine-grained soils with high moisture content, multiply the HP by Table 9. Holding Power of Deadmen in Loamy Soil.

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