Analytical investigation for stress measurement with the rheological stress recovery method in deep soft rock

Due to the difficulty and weakness of current stress measurement methods in deep soft rock, a new rheological stress recovery method of the determination of the three-dimensional(3D) stress tensor is proposed. It is supposed that rock stresses will recovery gradually with time and can be measured by embedding transducers into the borehole. In order to explore the applicability and accuracy of this method, analytical solutions are developed for stress measurement with the rheological stress recovery method in a viscoelastic surrounding rock, the rheological properties of which are depicted as both the Burger's model and a 3-parameter solid model. In such conditions, explicit analytical expressions for predicting time-dependent pressures on the transducer are derived. A parametric analysis is then adopted to investigate the influences of the grout solidification time and the mechanical properties of the grout layer. The results indicate that this method is suitable for stress measurement in deep soft rock, the characteristics of which are soft, fractured and subjected to high geo-stress.

INVESTIGATION INTO MORPHOLOGY, MICROSTRUCTURE AND PROPERTIES OF SBR/EPDM/ORGANO MONTMORILLONITE NANOCOMPOSITES

Rubber compounds based on styrene-butadiene rubber/ethylene propylene diene monomer blends of different compositions （60/40, 70/30, 80/20, 90/10, 100/0） reinforced with 1 wt%, 3 wt%, 5 wt% and 7 wt% organoclay （Cloisite 20A） were prepared on a two roll mill via a vulcanization process and characterized by several techniques. Results of X-ray diffraction showed expansion of the inter-gallery distance, and transmission electron microscopy （TEM） micrographs confirmed that the prepared nanocomposite samples have intercalated and partially exfoliated structures. Cure characteristics showed that, organoclay not only accelerates the vulcanization reaction, but also gives rise to a marked increase of the torque, indicating crosslink density of the prepared compounds increases at the presence of organoclay. Mechanical properties of samples received markedly increase by clay loading due to the good interaction established between nanoclay particles and polymer matrix as it was evidenced by SEM photomicrographs. At the same time, rheological properties showed that addition of nanoclay could improve storage modulus as well as complex viscosity of SBR/EPDM samples. The results of ozone test revealed that the ozone resistance of samples significantly increases as nanoclay or EPDM content increases.

RHEOLOGIC STUDIES ON CHEMICAL CROSS-LINKING KINETICS FOR LDPE

Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide （DCP） was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry （DSC） technique with different heating rates. The kinetic parameters of crosslinking reaction were calculated by both rheological and DSC measurements. The results reveal that with the increase of DCP contents, the apparent activation energy, Ea, ranges from about 140 kJ/mol to 170 kJ/mol and the order of crosslinking reaction, n, approaches unity. The influence of measurement frequency, on crosslinking reaction was also investigated. It can be found that n does not change with the increase of ωand Ea decreases slightly with the increase of ω