The response of laterally loaded piles is mainly influenced by soil-pile interaction in the shallower, unsaturated layers of surrounding soil above the water table. This study investigates the lateral load–displacement behaviour of model piles driven in unsaturated high-compressibility Kaolinite–Bentonite clay mixture. Model mild steel piles 360 mm and 480 mm in length ( \(L\) ) and 12 mm in diameter ( \(D\) ) with \(L/D\) ratios of 30 and 40 respectively, were used. The effect of soil suction, pile geometry, dry unit weight, water content, and undrained cohesion on the lateral capacity of model piles was investigated. The results revealed improved load–displacement behaviour with increased soil suction. A 33.33% increase in pile length, increased the lateral resistance by 10.68%, 35.14%, 43.03%, and 94.98% for the suction values of 3.90 MPa, 2.39 MPa, 0.96 MPa, and 0.80 MPa, respectively. The degree of reduction in lateral pile capacity with an increase in suction was strongly influenced by the dry unit weight, with insignificant influence of \(L/D\) ratio. Also, a positive correlation with a correlation coefficient ( \(r\) ) of + 0.51 was found to exist between undrained cohesion ( \({c}_{u}\) ) and soil suction. The study highlights the importance of considering the soil suction in design and analysis of laterally loaded piles. Considering the positive impact of soil suction in reducing the lateral response of piles in unsaturated soil, particularly in arid and semi-arid areas, can potentially lead to employing shorter pile lengths or reduced diameters while achieving the desired force–deflection demand.
