金属基复合材料的高应变速率超塑性

综述并评论了金属基复合材料的高应变速率超塑变形机制,描述了金属基复合材料在高应变速率超塑变形中的一些理化现象,说明了变形过程中的各种影响因素,总结了具有高应变速率超塑性能的金属基复合材料及其性能,并指出了在金属基复合材料的高应变速率超塑性研究方面的不足.

Uplift behavior and load transfer mechanism of prestressed high-strength concrete piles

Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.

锚杆局部黏结-滑移特性与围岩的相关性研究

为了探究围岩介质对锚杆局部黏结-滑移特性的影响,以两种不同类型的砂岩和钢管作为围岩介质制备锚固体进行中心拔出试验,分析了锚固体拔出失效形式、载荷-位移曲线、黏结应力沿锚固长度的分布特征。研究发现:锚固体拔出的失效形式表现为劈裂破坏与拔出破坏;锚固力与围岩的强度呈正相关,由大到小依次为钢管、黑砂岩、黄砂岩;载荷-位移曲线表现出明显的阶段性特征,曲线第一阶段的斜率与围岩相关;锚固界面滑移弱面形成于第一阶段结束时,且滑移弱面形态决定了曲线随后的发展趋势;随着拔出载荷的增加,黏结应力由沿界面均匀分布向非均匀分布过渡,黏结应力峰值位于锚固段自由端附近,峰值强度与围岩强度呈正相关。基于锚固体物理模型,探讨了围岩条件对锚固界面黏结-滑移特性的影响机理。试验结果可以为不同围岩条件锚固系统载荷传递机制和现场支护设计提供参考。