Enhancing the ability of the square footing to resist positive and negative eccentric-inclined loading using an inclined skirt

Abstract

Laboratory model tests were performed to investigate the behavior of shallow and inclined skirted foundations placed on sandy soil with R.D%=30 and the extent of the impact of the positive and negative eccentric-inclined loading effect on them. To achieve the experimental tests, it was used a box of (600×600) mm cross-sectional and 600mm in height and a square footing of (50*50) mm and 10 mm in thickness attached to the skirt with Ds=0.5B and various an angle of (10°, 20°, 30°). The results showed that using skirts leads to a significant improvement in load-carrying capacity and decreased settlement. In addition, when the skirt angle increased, the ultimate load improved. Load-carrying capacity decreased with increasing eccentricity and load inclination. For load inclination (Beta) 15° when the eccentricity changed from e=0.15B to e=0.05B, the load improvement percentages were (323.2 to 263%) and (214 to 220%). The settlement reduction factor was (83 to 78%) and (62 to 58%) for positive and negative eccentric-inclined loading, respectively. Also, the result showed that the positive effect on reducing soil-bearing capacity is more than the negative. Increasing eccentricity increases the improvement percentage for positive eccentric-inclined load and decreases for the case of negative eccentric-inclined load. Increased skirt angle will increase the Improvement factor (IR). When the skirt angle increased from 10° to 30° for an improved foundation with load angles of 5°, 10°, and 15°, the improvement factor (IR) increased from (2.53, 2.51, 2.4) to (3.45, 3.65, 3.97) and (2.43, 2.58, 2.54) to (4, 4.63, 5.3) for both negative and positive eccentric-inclined load respectively and settlement reduction factor for load angle 15° and skirt angle increase from 10° to 30° were 34% and 27% for positive and negative eccentric-inclined load respectively. The (IR) for the positive eccentric-inclined load is more than the negative eccentric-inclined load for all cases. In addition, the skirt angle of 30° significantly improved the improvement factor (IR).