Experimental Study on Mechanical Properties of Volcanic Ash Soils as Fill Materials for Barthfill Dams and Road Construction

为研究关东-壤土等火山灰黏结土作为填土坝和路面下路基土的土料，在碾压循环荷载作用下的强度降低（软化）、压实后的触变强度恢复、压实荷载在填土中的传递等力学特性，通过测量压实过程中的土压力和孔隙水压力，以及通过锥突和无侧限压缩试验测量填土材料强度的空间和时间变化，对模型填土进行了多次压实试验。充填材料的强度在压实达到一定程度时先增加，但在压实达到一定程度后，由于土骨架崩塌，强度逐渐降低，约为q值最大值的45%。循环三轴试验结果表明，模量、静、动变形模量是解释压实软化的较好指标。在模型压实试验中，由于强度数据的大离散，强度恢复特性难以识别。另一方面，实验室试验表明，易软化材料的强度回复率更高，而qc值和q值由于强度增加的反应不同，有时会显示出不同的强度回复率。

In order to study mechanical properties of volcanic ash cohesive soil like Kanto-Loam, when utilized as earth materials for earthfill dams and subgrade soil under the pavement, such as strength reduction (softening) due to cyclic loading of roller compaction, thixotropic strength regain after compaction, and transmission of compacting load in the fill, several roller compaction tests were performed for model earthfills by measuring earth and pore-water pressures during compaction and spacial and time-dependent changes of strength of fill materials by cone penetration and unconfined compression tests.Strength of fill materials increases at first as compaction proceeds up to a certain extent but decreases gradually after than due to the collaps of soil skelton, by approximately 45 percent of the maximum value in qu-value. According to the results of cyclic triaxial tests, qu-value and static and dynamic deformation moduli are good indices to explain softening due to compaction.Strength regain properties were hard to recognize in model compaction tests because of large scatters of strength data. Laboratory tests on the other hand gave some suggestions that the rate of strength regain is higher for materials easy to soften, and than qc-and qu-values sometimes show different results for strength regain because of their different reactions in strength increase.