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首页> 外文会议>Deep Foundations Institute 28th Annual Conference on Deep Foundations: Deep Foundations in Compressible Soil and Soft Rock >7- Foot Diameter Drilled Shafts in Weathered Rock: Design, Load Testing, and Construction
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7- Foot Diameter Drilled Shafts in Weathered Rock: Design, Load Testing, and Construction

机译：风化岩石中的7英尺直径钻孔轴：设计，载荷测试和构造

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The design of large diameter drilled shafts in weathered rock has always presented a challenge to the foundation engineers. Degree of weathering and load transfer mechanism through the rock are essential elements required for the design. From the Contractor's perspective specifying the right equipment and estimating the rate of drilling in the weathered rock are key elements for successful construction. The Delaware River Tramway Project has provided an opportunity to address the design and construction of drilled shafts in weathered rock. The Tramway, supported by twin 300-foot towers, will shuttle eight-person gondolas across the Delaware River in about four minutes. Each tower, founded on four high capacity drilled shafts, is designed to resist large axial and lateral loads. At the New Jersey tower, each 7-foot diameter shaft extends 145 feet deep and terminates in weathered Mica Schist. The shafts are situated in the Delaware River where the mud line is approximately 20 feet below Mean Low Water. Below the mud line, there exists a very soft, 20-foot thick layer of organic silt, followed by a 40-foot thick dense sand stratum. Below these sand and silt strata, a 70-foot thick layer of weathered Mica Schist underlies the entire site. Both skin friction and end bearing in the weathered rock stratum were utilized in the analysis to compute the axial capacity. AASHTO and the PennDOT design methodologies were utilized independently during design of the drilled shafts to verify the design. The drilling of large diameter drilled shafts embedded into weathered rock and situated in a marine environment provided a unique challenge in the construction. A permanent steel casing was installed for a specified depth and proper equipment was used to drill and keep the shaft open through the weathered rock. In addition, a 5000 kip Osterberg load test was performed on one shaft to verify design assumptions and confirm the shaft capacity. The results of the test were utilized to establish load transfer characteristics within the weathered rock and to develop foundation design parameters to be used for the remaining shafts.
机译：风化岩石中大直径钻杆的设计始终对地基工程师提出了挑战。风化程度和通过岩石的载荷传递机制是设计所需的基本要素。从承包商的角度来看，指定合适的设备并估算风化岩石中的钻孔速率是成功施工的关键要素。特拉华河电车轨道项目为解决风化岩石中钻探井的设计和施工提供了机会。由双300英尺高的塔支撑的电车轨道，将在大约四分钟内穿梭八人吊船穿越特拉华河。每座塔均建在四个高承载钻探轴上，旨在抵抗较大的轴向和横向载荷。在新泽西塔楼，每个直径7英尺的竖井延伸145英尺深，并终止于风化的Mica Schist。竖井位于特拉华河，泥线低于平均低水位约20英尺。在泥线以下，有一个非常柔软的20英尺厚的有机淤泥层，然后是一个40英尺厚的致密砂岩层。在这些沙子和淤泥地层的下方，整个站点位于一层70英尺厚的风化云母片岩上。在分析中，利用了风化岩层中的表皮摩擦力和端承来计算轴向承载力。在钻探轴的设计过程中，分别使用了AASHTO和PennDOT设计方法来验证设计。埋在风化岩石中并位于海洋环境中的大直径钻轴的钻孔给施工带来了独特的挑战。安装了永久钢套管以达到指定的深度，并使用适当的设备进行钻孔并保持杆身在风化岩石中敞开。此外，对一根轴进行了5000 kip的Osterberg载荷测试，以验证设计假设并确认轴容量。测试结果被用于建立风化岩石内的载荷传递特性，并开发用于剩余竖井的基础设计参数。

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