Physical-mechanical properties of microbially induced calcite precipitation-treated loess and treatment mechanism

Loess disintegration can lead to geotechnical engineering problems,e.g.,slope erosion,wetting-induced landslide,and hydroconsolidation.Microbially induced calcite precipitation(MICP)technique is a potential loess reinforcing method.This study investigated the physical-mechanical properties of MICP-treated loess and then explored the mechanism of loess modification by MICP.Here,loess first underwent MICP treatment,i.e.,mixing loess with Sporosarcina pasteurii and cementation solution(CS).Then,the effects of the CS concentration(0.2,0.6,0.8,and 1 M)on the physical and mechanical properties of the MICP-treated loess were tested.Finally,the static contact angle test,scanning electron microscopy(SEM),and X-ray diffractometry(XRD)were conducted to study the mechanism of MICP treatment on loess.Results showed the following property changes of loess after MICP treatment:the liquid limit decreased by 1.7%,the average particle size increased from 6 to 47μm,the specific gravity decreased from 2.65 to 2.43,the unconfined compressive strength increased from 37 to 71 k Pa,and the disintegration time increased from 10 to 25 min.Besides,the shear strength also increased,and the shear strength parameters(cohesion c and internal friction angle?)varied with the CS concentration.The static contact angle tests indicated that the water absorption ability of loess was reduced after MICP treatment.SEM and XRD results verified that the CaCO_(3)from MICP was attributed to the above results.The above findings explained the mechanism of MICP treatment of loess:the CaCO_(3)coats and cements the particles,and fills the pores of loess,improving the strength and water stability of loess.

The difference analysis of physical-mechanical properties of sediments in the central South Yellow Sea and Zhe-Min coastal area in China

The difference analysis of physical-mechanical properties of muddy sediments is made in the central South Yellow Sea and the Zhe-Min（Zhejiang Province to Fujian Province of China） coastal area. The results show that sediments in the two regions are both dominated by mud. There are perfect negative power function correlations between the water content and the density, the compression coefficient and the compression modulus; a good positive power function correlation between the liquid limit and the plastic limit, a perfect positive linear correlation between the water content and the void ratio, and a perfect polynomial function correlation between the miniature vane shear strength and the pocket penetration resistance. In general, compared with sediments in the Zhe-Min coastal area, sediments in the central South Yellow Sea possess high water content, high void ratio,low density, high plasticity, high compressibility, low shear strength. The causes of the differences between physical-mechanical properties of sediments are analyzed from the topographic features, material sources,hydrodynamic conditions, deposition rate, and material composition. Compared with the Zhe-Min coastal area,the central South Yellow Sea is far from the Mainland and low-lying; has poor hydrodynamic condition; the materials diffused to the area are less and dominated by fine clay, have the high content of smectite and organic matters. These factors lead to sediments of the central South Yellow Sea has the higher water content, the higher plasticity, the lower density, and the lower strength than sediments in the Zhe-Min coastal area.

Effect of Fertilization on Anatomical and Physical-mechanical Properties of Neosinocalamus Affinis Bamboo

In order to maintain soil fertility of Neosinocalamus affinis plantations,fertilizers of N,P,and K were applied.The anatomical and physical-mechanical properties of N.affinis bamboo wood from different fertilization treatments were measured.The aim of this study was to elucidate the effect of fertilization practice on the properties of N.affinis bamboo wood.The results revealed that the fertilization of P and K resulted in a slight reduction in fiber length.The application of P,K,and low level(0.3 kg/clump)of N fertilizers had no significant effect on the fiber morphology,while high level(0.9 kg/clump)of N fertilizer contributed to short fibers.The specific gravity was significantly decreased by fertilization,while the volume shrinkage was increased.Since the effect of various fertilization treatments had different influence patterns on the properties of N.affinis,specific evaluations on the quality of the fertilized bamboo wood should be performed prior to its utilization.

Studying the Curing Conditions of Unsaturated Polyesters from Secondary Polyethylene Terephthalate Alcoholysis Products

The technological properties of the curing conditions for unsaturated polyesters synthesized on the basis of the alcoholysis products of secondary polyethylene terephthalate and unsaturated polyesters used in the production of fiberglass pipes were studied. It is shown that unsaturated polyesters synthesized on the basis of alcoholysis products can completely replace imported resins of grades 196 and 196A in the production of fiberglass pipes.