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首页> 外文会议>Association of State Dam Safety Officials, Inc. 2002 Annual Conference Sep 8-11, 2002 Tampa, Florida >LYMAN DAM FAILURE FORENSICS AVOID MAJOR DESIGN CHANGES COSTS IN EARTH DAM REHABILITATION
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LYMAN DAM FAILURE FORENSICS AVOID MAJOR DESIGN CHANGES COSTS IN EARTH DAM REHABILITATION

机译：莱曼大坝故障取证避免了大坝修复中的主要设计变更和成本

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Lyman Dam, located in Apache County, Arizona, was designated to be unsafe due to concern that the steep main dam embankment and the spillway capacity were not in compliance with modern dam safety standards. Consultants provided the design for a downstream embankment raise, flattening of the downstream slope and a 12-foot thick toe buttress, underlain by wick drains, to stabilize the dam. This design was approved in 1999 by the Arizona Office of Dam Safety (AODS). During design development consultants and AODS staff were concerned about the possible presence of low strength soils in the foundation. However, site investigations indicated that the foundation soils were of moderate strength when undisturbed. Soon after construction started in 1999 the presence of an unusually weak, soft clay deposit was discovered in the downstream toe area of the new embankment. These weak soils appeared to have been deposited in a deep hole, scoured into the foundation during the 1915 piping failure of the original dam. The weak clay deposit required a major redesign and increase of the thickness of the buttress fill to 35 feet. Temporary surcharge fills were required to stabilize the toe of the buttress. Wick drains were also included under a major portion of all fills. Embankment construction was completed in two stages to allow time for first stage fills to consolidate and strengthen the foundation soils for the second stage of construction. Increased construction costs for the dam embankment were on the order of $500,000 and were reallocated from the planned spillway reconstruction. The planned concrete ogee spillway was deleted and the existing concrete weir spillway was widened to provide flood capacity by construction of a grouted riprap weir section and fuse plug. The question from the authors is "Could or should" the consultants and AODS staff have predicted and investigated more specifically for the location of the unusually weak clay deposit which in-filled the 1915 scour hole; thus, avoiding the major design changes and unplanned increases in embankment construction costs?
机译：由于担心陡峭的大坝堤坝和溢洪道容量不符合现代大坝安全标准，位于亚利桑那州阿帕奇县的莱曼大坝被指定为不安全。顾问提供了下游堤防抬高，下游斜坡的平坦化和12英尺厚的脚趾支撑（由灯芯排水管支撑）的设计，以稳定大坝。该设计于1999年由亚利桑那大坝安全局（AODS）批准。在设计开发期间，顾问和AODS工作人员担心地基中可能存在低强度土壤。但是，现场调查表明，基础土在不受干扰时强度中等。 1999年开始施工后不久，在新路堤的下游脚趾区域发现了异常软弱的粘土沉积物。这些薄弱的土壤似乎沉积在一个深孔中，在1915年原始大坝的管道故障中冲刷到了地基中。稀薄的粘土沉积物需要进行重大的重新设计，并将支撑物的厚度增加到35英尺。需要临时附加费以稳定支撑脚趾。虹吸排水管也包括在所有填料的主要部分下。路堤施工分两个阶段完成，以便有时间进行第一阶段的填充，以巩固和加强第二阶段施工的基础土壤。大坝堤防的建设成本增加了约500,000美元，并从计划的溢洪道改造中重新分配。计划中的混凝土胶泥溢洪道被删除，现有的混凝土堰溢洪道被扩建，通过建造灌浆的riprap堰段和保险丝塞来提供洪水能力。作者的问题是，顾问或AODS员工是否“应该或应该”预测并更具体地调查填充于1915年冲刷孔中的异常稀疏的粘土矿床的位置。因此，要避免进行重大的设计变更以及路堤建设成本的计划外增加？

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