Microstructure unit of the offshore clay— clay domains contains a large amount of intragranular pores

of which the diameters are small to nanoscale. These pores have an important influence on the physical indices

water stability

expansion and shrinkage characteristics. However

general methods are difficult to accurately describe intragranular pore characteristics. The scanning electron microscopy (SEM)

mercury porosimetry(MIP)

nitrogen adsorption(NA) are used on the Zhanjiang clay to study its microscopic pore characteristics and control factors of pore distribution. The relationship and sensitivity analysis of the microstructure and physical parameters

mechanical behavior are established. Results show that the Zhanjiang clay has the unusual combination of poor physical properties and good mechanical properties; it is a kind of high sensitivity and strong cementation structural clay

the main mechanism was disorderly orientation and open flocculation structure with cementation bond; furthermore

pore structure is a space frame system which has higher strength and stability of the side-surface-angle connection. Therefore

the retention phenomenon of mercury-ejection curve and hysteretic loop in adsorption-desorption isotherm occurring because of special space frame system and ‘ink bottle’ type pore. In addition

the research shows that

the combination of SEM

MIP

NA methods can accurately

qualitatively and quantitatively evaluate overall pore system characteristics of offshore clay.