Geomechanical and water vapor absorption characteristics of clay-bearing soft rocks at great depth

The geological and physico-mechanical properties characterization of deep soft rocks is one of the critical scientific issues for deep soft rock engineering. In the present study, X-ray diffraction(XRD) analysis,scanning electron microscope(SEM), and mercury intrusion porosimetry experiments were carried out to investigate the mineral compositions, microstructure and porosity characteristics of the 13 claybearing soft rock samples collected from a deep coal mine in China. Water vapor absorption and uniaxial compressive experiments were also performed to examine water absorption characteristics and waterinduced strength degradation effect of the investigated deep soft rock samples. The results show that the dominant mineral components in mudstone, coarse sandstone and fine sandstone samples were calcite, quartz and clay respectively. The contents of clay minerals in all samples were relatively high and ranged from 12.3%(N-4) to 56.5%(XS-1). Water vapor absorption processes of all the soft rock samples follow an exponential law which is very similar to the water vapor absorption behavior of conglomerate samples reported in our earlier study. Correlation analyses also suggested that there were good positive correlation relationships between water absorptivity and clay minerals for both mudstone and sandstone samples. Furthermore, it was found that vapor absorption was not correlated with the porosity for mudstone, however, positive correlation relationship was found between them for sandstone. Correlation analysis between UCS, modulus of elasticity and water content demonstrated that both of them tend to decrease with the increase of their water content due to water absorption.

Hydrophilic characteristics of soft rock in deep mines

A series of water absorption tests on dried soft rock have been conducted by the intelligent testing system for water absorption tests in deep soft rock, including tests of water absorption with and without pres- sure. The results show that the water absorbing capacity of rock with a certain pressure is larger than that of rock without pressure： however, the relationship between the water absorbing percentage and the time can be expressed by w（t） = a（l - e^-bt）. In hi-logarithmic coordinates, the hydrophilic relationship with time in tests with pressure could be characterized by linearity, while they present concave or convex in tests without pressure. Based on the hypothesis that each influential factor is irrelevant and they have a linear correlation with the water absorbing capacity, we calculated the weight coefficient of each factor according to experimental results under different conditions. The calculations demonstrate that the effec- tive porosity, content of smectite and kaolinite are all positively correlated with the water absorption capacity of rock; meanwhile, the fractal dimension of the effective pores presents a negative correlation with the water absorption capacity of rock. The water absorption capacity with pressure increases with increasing illite, chlorite and chlorite/smectite formation and a decrease in illite/smectite formation and the fractal dimension of the effective pores, while it is opposite in tests without pressure. The weight coefficient of smectite is smallest among positive factors, and the fractal dimension of the effective pores is the smallest amongst the negative factors.

Reducing dietary sodium of dairy cows fed a low-roughages diet affect intake and feed efficiency,but not yield

Wastewater from dairy farms has become a major environmental and economical concern.Sodium residue in treated and untreated wastewater from dairy farms used for irrigation can lead to soil and groundwater salinization,with the risk of soil degradation.We examined the effect of reducing sodium fed to mid to late lactating cows from 0.61%(high sodium[HS])to 0.45%(low sodium[LS])of dry matter on dry matter intake(DMI),milk and milk-component yields,eating behavior,apparent total track digestibility,feed efficiency,and sodium excretion into the environment.We randomly assigned 28 multiparous high-yielding(>35 kg milk/d)cows to 1 of 2 treatment groups(LS or HS)in a crossover design,with 7 d of adaptation and 28 d of data collection.Reducing sodium in the diet reduced sodium intake from 171 to 123 g/d while lowering sodium excreted in the manure by 22%.Energy corrected milk(ECM)yield(37.4 kg/d)and sodium excretion in the milk(33.7 g/d)were similar for both groups.The DMI of LS cows was lower than that of HS cows(27.3 vs.28 kg/d)and consequently,feed efficiency of the LS cows was higher(1.40 vs.1.35 ECM/DMI).Eating rate,meal and visit frequency,and eating time were similar for both treatments;meal and visit duration were longer for the HS cows,and meal and visit sizes tended to be larger.Digestibility of DM and amylase-treated neutral detergent fiber remained similar.Based on the results of this study,and discussed considerations,we recommend lowering the dietary sodium content for mid to late lactating cows in commercial herds to 0.52%of DM,in order to reduce sodium excretion to the environment via urine.