Similar simulation device for unloading effect of deep roadway excavation and its application

The unloading effect of the excavation of deep roadways has been considerably studied, but most research methods have been limited to numerical simulations and field measurements. Only a few have adopted experimental methods for similar simulations. On the basis of the theory of mechanics,the testing system is designed considering initial geostress and dynamic unloading. The system includes an impact unloading gear and in-situ stress loading equipment, and a designed three-link structure and the impact hammer can effectively realize the dynamic excavation of roadways.Meanwhile, a cyclic excavation similar simulation experiment on a deep roadway is conducted in a laboratory. The testing system and the relevant monitoring facilities are utilized, and the unloading effect inside the surrounding rock under the cyclic dynamic excavation is studied. Results show that the cyclic dynamic excavation causes significant unloading only in the nearby rock mass, and the unloading indicators show nonlinear changes.Moreover, when the lateral pressure coefficient is 1.2,the damage is concentrated on both roadsides due to the excavation unloading. Meanwhile, the damage gradually decays as the span increases.

生物质填充型降解塑料原料及改性方法研究进展

为解决不可降解塑料对环境带来的危害,不同类型可降解塑料的研究迅速兴起,生物质填充型降解塑料是常见的一种。文章总结了不同原料与不同改性条件下生物质填充型降解塑料及其应用进展。原料方面按填料的不同,分为淀粉、木质纤维素、蛋白质、微藻等生物质填料。改性方法主要分为物理改性、化学改性以及增容剂的加入。介绍了生物质填充型降解塑料在工业及日常领域的一些应用。