The Indo-Gangetic Quaternary alluvium predominantly consists of clay, silt, or sand layers as deposited by these major rivers and their tributaries. Sometimes, silts are intruded into the sand matrix, or plastic clay percolates into the sand matrix. The percolated plastic clay formed the alluvial lumps in the sand matrix at insitu conditions due to groundwater fluctuations. From preliminary studies, it has been observed that these conditions affect the dynamic behaviour of these soils. However, the dynamic properties of these soils are not well documented. Therefore, a comprehensive study has been initiated here to estimate the dynamic behaviour of these various types of soil available in this Indo-Gangetic quaternary alluvial deposit. A series of large-strain cyclic triaxial tests and small-strain bender element tests were performed in the soil dynamics laboratory at IIT Patna. Samples were prepared by adding varying percentages (5%, 10%, 20%, and 30%) of non-plastic silt with sand, and mixing various percentages of clayey lumps with sand to evaluate the effect of these soil conditions. This methodology was used to examine the impact of silt and clay intrusion in the sand matrix on the liquefaction susceptibility of the soil. Findings indicate that lumped sandy soil demonstrates a higher susceptibility to liquefaction than clean sand. A novel aspect of this study is the comparison of dynamic shear modulus and damping ratios for clean sand and sand-lump mixtures, analysing the effects of saturation levels, silt content, and clayey lump percentages under cyclic loading. Simultaneously, bender element tests demonstrated that shear wave velocity increases with the increase in lump content, confining pressure, or loading frequency in the sandlump mixture samples. The results contribute valuable insights into the behaviour of Gangetic alluvial soil under dynamic loading, enhancing geotechnical and seismic risk assessment in similar geological environments.