Characterizing Optimum Casing Configuration for Laterally Loaded Micropiles with Inclined Condition

Micropile is vulnerable to lateral load due to the small diameter configuration. Inclusion of a steel casing can be an effective option to enhance the lateral load capacity of micropile, yet not quantified in detail. In this study, the reinforcing effect of casing for laterally loaded micropile is investigated considering the inclined condition of micropile. A series of the finite element analysis were performed to simulate laterally loaded micropiles for various configuration conditions. The maximum bending moment (M_max) and its location (Z_max) became smaller and shallower, respectively, when micropile was inclined at an angle of θ, which is advantageous in design. For micropile with a casing, the lateral load capacity (H_u) increased as casing length (L_c) increased, and the effect of θ was similar for all cases with different length ratios of casing and micropile (i.e., L_c/L_p). H_u increased by 50% to 60% for L_c/L_p of 0 to 0.3, respectively. For L_c/L_p > 0.3, the values of both H_u and M_max did not change significantly for all θs. Therefore, L_c/L_p = 0.3 was proposed as an optimum casing length that yields the most economical yet most enhanced stability condition. A design equation was proposed to estimate the lateral load capacity of inclined micropiles with a casing.