Mechanochemical phenomena in microporous bodies, including initial compression in a vacuum, additional compression in the initial gas adsorption stage, and expansion during subsequent adsorption, were analyzed under the constraint of mechanical equilibrium using adsorbate pressure tensor in pores of various shapes. Precise calculation of deformation was performed for cylindrical and spherical pores. Pore surface tension was shown to be responsible for initial compression of adsorbent in a vacuum and its expansion during gas adsorption. Insignificant additional compression of adsorbent in the initial adsorption stage was attributed to specificity of the adsorbate pressure tensor in a pore, effect of temperature, and chemisorption (provided that active centers are present).