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).