Negative pore water pressure plays a significant role in the behavior of clay minerals, particularly kaolinite and bentonite. This work enhances the impact of negative pore water pressures on these two types of clay minerals, highlighting their influence on soil properties and engineering considerations. Kaolinite and bentonite, both common clay minerals, exhibit distinct responses to negative pore water pressures due to their differing mineralogical compositions. The interaction between negative pore water pressure and these clay minerals is crucial for predicting and managing soil behavior in geotechnical engineering. The theoretical calculation of negative pressure assumes that, for any particular degree of saturation, the pores are filled with water uniformly to a particular level of pore size (average pore size) which is always less than the pore size that is actually filled in the test specimen. Therefore, the theoretical calculations have serious limitations in that and hence in the present experimental work involved the preparation of artificial mix proportions of Kaolinite-Sand, Bentonite-Sand, and Kaolinite-Bentonite-Sand. These mixtures were then exposed to a direct shear test with different energy levels, including light (LC) and heavy compaction (HC). To calculate the negative pore water pressure of the prepared mix proportions, Mohr’s Coulomb failure envelope was extended to the Normal stress axis. The negative pore water pressure for kaolinite-sand mix proportions increases by 65%, whereas for bentonite-sand mix proportions it increases by up to 294%. Furthermore, the negative pore water pressure experiences a significant rise of 352% when considering different mix proportions of kaolinite-bentonite-sand.