动荷载作用下冻土试验技术及冻土变形初步研究

Preliminary study on testing techniques and deformation of frozen soil under dynamic loading

随着季冻区公路工程建设规模不断扩大,路基在冻融及车辆荷载(尤其重载)协同作用下翻浆、沉陷等灾害现象频繁出现,需要对其致灾机理进行深入研究。本文采用英国GDS冻土动静三轴仪对季冻区路基土开展了常温、-5℃及-10℃三种环境下的动变形试验研究。主要工作有:(1)针对GDS仪器在试验中出现的围压进气孔及加载杆易冻结等实际问题,提出了采用耐压密封胶及硅胶干燥剂等处置方法,保证了冻土负温试验的顺利开展;(2)开展了常温下路基土动变形试验。在相同循环作用次数条件下,存在动应力临界值。当动应力幅值超过此界限,土体残余应变逐渐增大,直至破坏;反之,则土体应变速率逐渐降低,残余应变最终趋于稳定;(3)开展了-5℃及-10℃条件下路基土动变形试验。试验表明:同一动应力幅值作用下,随土体温度降低,其残余应变减小,但即便同在负温条件下,土的应变速率及最终值也有很大差异。试验得到的新认识对季冻区公路设计及灾害防治有一定指导意义。

With the construction scale of highway in seasonal freezing regions extends continuously, hazards like frost boiling and subsidence of subgrade under circles of freezing and thawing, action of traffic load （ especially the overloading） appear more frequently, it is essential to study out the mechanism behind it. Studies of dynamic de- formation to the subgrade soil at room temperature, -5 ℃ and - 10 ℃were conducted on the GDS triaxial appa- ratus, on which frozen soil can be tested. The main of the air inlet for cell pressure and the loading rod work of this paper is as follow ： （ 1 ） According to the questions are easily frozen during the tests, pressure-tolerant sealant and silica-gel desiccant were applied, which ensures the experiments go smoothly. （2） Tests of subgrade soil＇ s dynamic deformation at room temperature were conducted, which indicated that there is a critical value for dynamic stress when the times of circle are the same. When the amplitude of dynamic stress exceeds the value, the residual strain will increase constantly until the damage of specimen. Otherwise the strain rate will gradually die down, and the re-sidual strain finall rature, - 5 y tends to be stable. （3）Defn ℃ and - 10 ℃ is studied. It s residual strain tends to difference between strain rate standing gained via the tests hell）fill to the disaster t）e decreased with and the final value will be useful to th rmation properties of subgrade soil under dynamic load at normal is found that at the same level of dynamic stress amplitude, the the decreasing temperature. However, there are still considerable , even both of them were at negative temperature. The new undere design of highways in seasonal freezing regions, and it is also and accident reduction