5.3.2 Clough and O’Rourke's method

Clough and O’Rourke（1990）proposed various types of envelopes of excavation⁃induced ground surface settlements for different soils on the basis of case studies.According to their studies，excavation in sand or stiff clay tend to produce triangular ground surface settlement.The maximum settlement will be found near the retaining wall.The envelopes of ground surface settlement are as shown in Figures 5.9（a）and 5.9（b），whose influence ranges are separately 2He and 3He where He is the final excavation depth.Excavation in soft to medium clay will produce a trapezoidal envelope of ground surface settlement，as shown in Figure 5.9（c）.The maximum ground surface settlement occurs in the range of 0＜d／He＜0.75 while 0.75＜d／He＜2.0 is the transition zone where settlement decreases from the largest to almost none.Basically，the curves in Figure 5.9 are also envelopes.