An Unconstrained Sliding Friction Model and an Application to the Folsom Dam

无约束滑动摩擦模型及其在福尔瑟姆大坝的应用

• 批准号: 0408389
• 负责人: Steven Glaser
• 金额: $ 28.89万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408389&HistoricalAwards=false
• 关键词: Unconstrained; Sliding; Friction; Model; Application

We are undertaking a fundamental curiosity driven project that has immediate implications for public safety. The intellectual merit rests in development of an analytical technique to model laterally unconstrained shear displacement of a gravity loaded block. The public safety issue concerns safety of the Corps of Engineer's Folsom Dam. Completed in 1955, the structure is located just east of Folsom, California, and holds back over one million acre-feet of water. Between Folsom Dam and downtown Sacramento, the American River flows through one of the most densely populated regions in California. Recent calculations made with original surface topographic data have produced some unacceptably low factors of safety for seismic scenarios involving independent sliding of the monoliths, in which case there might be little or no lateral constraint on a given block. Co-P.I. Richard Goodman is a member of the Folsom Dam Outlets Modification Project external review panel, giving us unique access to existing topographic data on surface profiles beneath the Folsom monoliths. This enables us to approximately duplicate actual surface profiles in test samples, as well as to use the topographic data to analytically estimate the stability of the dam.There is currently no general analytical model for laterally unconstrained sliding, even if full topographic information is available for the entirety of both sliding surfaces (as in the case of Folsom Dam). We are developing a mathematical sliding model that takes into account the unconstrained boundary conditions, offering a prediction of the 3-D failure (dilation) route. We are utilizing the properties of functionals and examining relatively simple tests on rough surfaces to develop an analytic energy-based equation describing unconstrained sliding. Minimizing virtual work and setting constraints which reflect the interaction of the surfaces between which contact points are sliding allows the calculation of the lowest energy path of each sliding point along the surface. This methodology is being extended over the candidate set of likely contact points to describe the net motion of a rough block sliding over a rough surface, which is not a trivial problem because the contacting set of asperities changes with displacement. The equation will be empirically refined and extended to the semi-constrained case.Experimental verification of the proposed model is being carried out using a simple but entirely new device, which allows virtually unconstrained lateral motions in the principle directions. This device is being incorporated into the specialized acoustic emission (AE) shear testing facility built for a previous NSF grant. The upper loading platen for the normal load has embedded within 24 Glaser/NIST-type high-fidelity AE sensors which yields full quantitative time-domain waveforms from local movements on the sliding surfaces. The overdetermination of the present problem allows for extremely accurate source location in 3-D space and inversion for the detailed source kinematics expressed as a moment tensor.Besides the life safety issues, broader impacts include the furthering of our understanding of frictional behavior of unconstrained blocks. This will provide a tool for many other researchers in a variety of fields. Basic knowledge of the interaction and behaviors of interacting asperities will grow out of the inversion of AE data for source kinematics, which has important implications for fault rupture modeling and energy release estimates. This work is a direct outgrowth of the P.I.'s previous work.The P.I. works closely with Berkeley's Center for Underrepresented Engineering Students (CUES), in addition to the SUPERB and CAMP programs. We are presently using the Berkeley Edge to assist in finding qualified graduate students for the proposed project. The Berkeley Edge, partially funded by the National Science Foundation, is a recruitment, retention, and advancement program for traditionally underrepresented minority graduate students in science, mathematics, and engineering. In addition, the P.I. directly involves undergraduate students in all aspects of his research program (4 currently), and supervises students with backgrounds in electrical engineering, physics, and IEOR. This interdisciplinearity forces all the students to grow technically and to respect other disciplines and ways of approaching problems.

我们正在进行一个基本的好奇心项目，对公共安全具有直接的影响。 智力优点基于开发分析技术，以模拟重力负载块的侧向不受限制的剪切位移。 公共安全问题涉及工程师福尔索姆大坝的安全。该结构于1955年完工，位于加利福尼亚州佛森（Folsom）的东部，持有超过一百万英亩英尺的水。 在佛森（Folsom）大坝和萨克拉曼多市中心之间，美国河流经过加利福尼亚人口最密集的地区之一。 对于涉及整体独立滑动的地震场景，使用原始表面地形数据进行的最新计算产生了一些不可接受的安全因素，在这种情况下，在给定的块上可能几乎没有或没有横向约束。 Co-P.I。理查德·古德曼（Richard Goodman）是Folsom大坝插座修改项目外部审查面板的成员，使我们独特地访问了Folsom Monoliths下面的表面配置文件的现有地形数据。 这使我们能够在测试样品中大致复制实际的表面曲线，并使用地形数据来分析估计大坝的稳定性。目前，即使在两个滑动表面上都可以使用全部的整个地形信息（如Forsom dam deforsom domsom domsom doe of Folsom dam dofe of Forsom dam dofe of Folsom dom，即使全面的地形信息都可以使用。 我们正在开发一个数学滑动模型，该模型考虑了不受限制的边界条件，并提供了3-D故障（扩张）途径的预测。 我们正在利用功能的属性，并在粗糙表面上检查相对简单的测试，以开发一个基于分析能量的方程式，描述了不受约束的滑动。 最小化虚拟工作和设置约束，这些限制反映了接触点在滑动之间的表面相互作用，可以计算每个滑动点沿表面的最低能量路径。 该方法正在扩展到可能的接触点集，以描述粗糙的块在粗糙表面上滑动的净运动，这不是一个琐碎的问题，因为一组浅层的接触集随位移而变化。 该方程将在经验上进行完善并扩展到半约束的情况。对拟议模型的实验验证是使用简单但全新的设备进行的，该设备允许在原理方向上几乎不受限制地横向运动。 该设备已被纳入专门的声发射（AE）剪切测试设施中，为先前的NSF拨款建造。 正常载荷的上载压板已嵌入24个Glaser/NIST型高保真AE传感器中，该传感器可从滑动表面上的局部运动产生完整的定量时间域波形。 对本问题的过度确定允许在3-D空间中极为准确的源位置，并为详细的源运动学表达为时刻张量。Besides的生命安全问题，更广泛的影响包括我们对我们对不受约束块的摩擦行为的理解的进一步。 这将为许多领域的许多其他研究人员提供工具。 相互作用的相互作用和行为的基本知识将从源运动学的AE数据的反转中增长，这对故障破裂建模和能量释放估计具有重要意义。 这项工作是P.I.先前工作的直接产生。除了出色的和营地计划外，还与伯克利代表性不足的工程专业学生（CUES）密切合作。 我们目前正在使用伯克利边缘来协助为拟议项目找到合格的研究生。由国家科学基金会（National Science Foundation）部分资助的伯克利（Berkeley Edge）是一项招聘，保留和进步计划，用于传统上代表性不足的科学，数学和工程学的少数群体研究生。 此外，P.I.直接参与其研究计划的各个方面的本科生（目前为4个），并监督具有电气工程，物理和IEOR背景的学生。 这种跨学科性迫使所有学生在技术上成长，并尊重其他学科和解决问题的方式。