Collaborative Research: Dynamic behavior of slickensided surfaces

“滑面”是在坚硬的粘土中形成的软弱表面，由于大的剪切位移-在50毫米到250毫米的数量级-集中在一个离散的滑动表面上。板状粘土颗粒与滑动表面平行排列，从而形成光滑的表面，其抗剪强度远低于形成光滑表面的相邻粘土的强度。与邻近的粘土相比，这种低抗剪强度的结果是，光滑的破裂面很可能是地震期间位移的地点。然而，目前还没有关于光滑表面在地震中遭受快速循环荷载时的行为的研究。因此，工程师在估计地震变形分析的强度时必须依靠假设和判断，而这些在执业工程师之间差别很大。例如，在加利福尼亚北部的一个特定项目中，关于应该使用的抗剪强度的不同意见导致了边坡稳定的建议，其成本相差十倍。目前，还没有办法确定其中一种设计是否存在危险的不足，或者另一种设计是否存在浪费。本研究项目的广泛影响包括本科生和研究生有机会参加弗吉尼亚理工大学的实验室实验，大一到大四的学生有机会观察加州大学戴维斯分校的离心机实验，并作为助理准备离心机模型。加州大学戴维斯分校和弗吉尼亚理工大学都有非常积极的项目，通过加州大学戴维斯分校的少数族裔工程研究机会，少数族裔工程项目办公室，以及与弗吉尼亚理工大学历史上的黑人学院和大学的联盟，招收少数族裔学生参与研究。该项目还包括与新ata大学的Binod Tiwari博士的积极合作，他在所涉及的实验类型方面有丰富的经验，并将在弗吉尼亚理工大学和加州大学戴维斯分校度过一段时间，这将有助于在日本和美国的研究人员之间建立更密切的关系。

"Slickensides" are surfaces of weakness formed in stiff clays as a result of large shear displacements - on the order of 50 mm to 250 mm - concentrated on a discrete surface of sliding. Platy clay particles become aligned parallel to the surface of sliding, resulting in the formation of a smooth surface with shear strength that is much lower than the strength of the adjacent clay through which the slickensided surface forms.As a result of this low shear strength in comparison with the adjacent clay, slickensided rupture surfaces are likely loci of displacements during earthquakes. However, there have been no studies of the behavior of slickensided surfaces when subjected to the rapid cyclic loading that occurs during earthquakes. As a result, engineers must rely on assumption and judgment when estimating strengths for seismic deformation analyses, and these vary considerably among practicing engineers. For example, for one particular project in northern California, the difference of opinion regarding the shear strength that should be used resulted in recommendations for stabilization of the slopes that differed in cost by a factor of ten. At present, there is no way to determine whether one of these designs was dangerously inadequate, or the other was wasteful overkill.The broader impacts of this research program include opportunities for undergraduate and graduate students to participate in the laboratory experiments at Virginia Tech, and for freshman through senior-level students to observe the centrifuge experiments at UC Davis, and to work as assistants in preparing the centrifuge models. Both UC Davis and Virginia Tech have very active programs to recruit minority students to participate in research through the Minority Opportunities for Research in Engineering at UC Davis, and the Office of Minority Engineering Programs and coalition with Historically Black Colleges and Universities at Virginia Tech. The project also involves an active collaboration with Dr. Binod Tiwari of Niigata University, who has considerable experience in the types of experiments involved and will spend time at Virginia Tech and UC Davis, which will help to establish closer relationships between researchers in Japan and in the United States.