Advances in Civil Engineering / 2018 / Article / Tab 4 / Research Article
Emergency Trench Shoring and Rescue: A Simplified Method for Calculating Lateral Earth Pressures Table 4 Use of the T-L method for different failure scenarios. The clay properties bracket the range of plausible Type C clays that can exhibit the observed failure geometry.
Scenario 1: Figure 3 Scenario 2: Figure 4 Silty sand Sand Clay Clay Sand Sand Clay Clay Relative strength classification Meduim dense Dense Medium stiff Soft Dense Loose Medium stiff Soft Relative saturation classification Moist Saturated Saturated Saturated Moist-dry Saturated Saturated Saturated Undrained shear stength, S u (psf) — — 325 100 — — 650 200 Active earth pressure coefficient, k a 0.33 0.33 1 1 0.33 0.33 1 1 Unit weight, γ (pcf) 125 133 110 100 130 125 110 100 Maximum L (ft) 3 3 3 3 9 9 9 9 5 5 5 5 6 6 6 6 H (ft)6 6 6 6 12 12 12 12 Coulomb earth pressure 742.5 790.02 30 1200 3088.8 2970 120 4800 Q = wP a (kips)3.7 4.0 0.2 6.0 18.5 17.8 0.7 28.8 T-L method: ft (kips)3.3 3.3 3.3 3.3 9.9 9.9 9.9 9.9 N 4 4 4 4 6 6 6 6 R T-L = nR s T-L (kips)13.2 13.2 13.2 13.2 59.4 59.4 59.4 59.4 Maximum braced excavation pressure per strut [6 : Sand: P = 0.65γHk a (psf)160.9 171.2 334.6 321.8 Clay: γH /S u 2.0 6.0 2.0 6.0 γH /S u < 4 P = 0.3γH (psf) 198.0 396.0 γH /S u > 4 P = γH − 4S u (psf) 200.0 400.0 Q max = P × 4 ft × 4 ft (kip per strut)2.6 2.7 3.2 3.2 5.4 5.1 6.3 6.4
