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Subgrade stabilization is crucial for forest road construction, especially in Northeast China and the Russian Far East, with great economic growth potential. This study explored a novel and green solution of integrating biochar (BC), polyacrylamide (PAM), and straw fiber (SF) in the form of a ternary composite for stabilizing forest subgrade soil in cold regions. Using central composite design-based response surface methodology, the optimal mix ratio design was obtained, and the composite stabilizer was designated as BPS. Afterward, the stabilizing performance of BPS was studied by conducting an unconfined compression strength (UCS) test. The results showed that the optimum composition of BC:PAM:SF stood at 81:9:10. The UCS and deformation modulus with 3% BPS at 28 days reached 565.42 kPa and 17.24 MPa, respectively, which were 3.36 and 6.05 times higher than those of the untreated samples. The BPS-treated soil also possessed better resistance to freeze–thaw cycles. The freezing–thawing-induced loss ratio of strength was 49.3% lower than that of natural soil. Moreover, empirical models for the UCS of BPS-stabilized soil, as well as its relationships with the modulus, were established and validated by data in the literature. Finally, the "filling, cementing, and reinforcing" stabilization mechanism of BPS was elucidated by scanning electron microscopy analysis. [ABSTRACT FROM AUTHOR]

Stratified pumping can obtain accurately hydrogeological parameters, and the effect of stratified water stop determines the success of stratified water pumping. To summarize the research achievements of the stratified water stop, on the basis of literatures published in recent years, with the method of drawing, analysis, we summarize the layered water stop technology research status quo, and point out existing problems and developing trend. Research results show that: “variable diameter and different steps to stop water”, “one hole with the same diameter to stop water” can achieve stratified water stop, of which “variable diameter and different steps to stop water” outside the casing mainly fills with gravel and clay ball, often uses glue plug device to stop water inside the casing, Packer is mainly used in the stop water of “one hole with the same diameter to stop water”, which is the development trend of stratified water stopping technology. The research results provide a reference for project of the stratified water stop.

Building fire will seriously threaten human safety. Silica aerogel with low thermal conductivity and thermal stability as fire-retardant material has been widely used in building fireproof structures. However, the natural fragility of silica aerogel will limit its application. In this work, the effects of faults on the thermal stability of silica aerogel are studied by molecular dynamics simulation with large simulation time (20 ns). Additionally, the atomic model of silica aerogel with random faults is built by a straining structure (tensile strains are 10%, 20%, 30%, and 40%). It is found that when the tensile strain is less than 20%, the silica backbone can remain stable. The effects of faults on the thermal stability can be neglected. The silica backbone thermally vibrates during the heating process. However, when the tensile strain is over 30%, it is observed that the faults will enhance the silica backbone merging. Silica aerogel can be stable under 800 K. It is believed that the results of this study will pave the way for the development of fireproof materials. [ABSTRACT FROM AUTHOR]

Coal mine fires have continuously remained the primary disasters in coal mining worldwide. Cement-based inorganic foam concrete, e.g., for engineering filling and coal mine fire extinguishing, has become the first choice for responding to such fires. The objective of this study was to propose quick-solidifying foamed concrete materials based on laboratory tests, and to test the properties of these materials. The stability of a foamed slurry and solidified stone of a quick-solidifying foamed concrete were tested, along with the rheological properties, curability, shrinkage, high-temperature resistance, and cracking of the slurry during solidification. The laws and values of these characteristics were obtained. The results finally show that the quick-solidifying foamed concrete developed in this study has good performance with regard to filling and fire prevention in the large spaces of a mine.