RUI: Pervious Concrete Piles: An Innovative Ground Improvement Alternative

该奖项由2009年《美国复苏和再投资法案》(公法111-5)资助。透水碎石桩(即压实砂桩、碎石桩和夯实碎石桩)通常用于支撑在承受静力和地震荷载的软土或松散土上建造的建筑物和公路设施。虽然透水碎石桩的使用提高了固结速度，降低了液化势，提高了承载力和稳定性，减少了不良土体的沉降，但这种桩的刚度和强度较低，这取决于周围土体的性质。因此，颗粒桩在非常软的粘土和粉土中以及在有机和泥炭土壤中的应用有限。这项研究的重点是开发一种新的地基处理方案，使用透水混凝土桩来提供高渗透性，同时提供与周围土性无关的高刚度和高强度。与散体桩的特性相比，透水混凝土材料具有类似的渗透性，强度是其强度的十多倍，并且模数增加了两个数量级。透水混凝土的弹性模数和强度较高，在不影响高渗透性的优点的情况下，改善了桩的荷载传递和承载能力。使用透水混凝土材料最终将减少所需的面积替换率，这将显著缩短施工时间和成本。透水混凝土桩具有不依赖于周围土体约束的强度和刚度特性，将为非常软的粘土和粉土、有机土和泥炭土提供一种有效的地基加固方法。此外，透水混凝土桩可以用纵向耐腐蚀钢筋加固，以提高其在地震荷载作用下的延性和性能。研究目标集中在开发用于地基加固的透水混凝土混合料，并通过试验表征几种施工程序对土和桩的性质以及土-桩相互作用的影响。利用仪器和先进的传感器进行小规模的实验室试验，以了解安装程序对垂直、扬拉、横向和路堤荷载条件下透水混凝土单桩和群透水混凝土桩性状的影响。分析工作的重点是开发计算模型，通过三个阶段准确地预测透水混凝土桩系统的行为：桩的安装、固结和在役荷载。分析模型将使用实验室材料和桩载荷测试的结果进行校准，并将开发供研究人员使用的复杂分析方法和为执业工程师推荐的简化分析工具。拉斐特学院的土-结构相互作用装置是由国家科学基金-S重点研究仪器计划资助的，将用于进行试验和分析研究。这项研究将从Geopier基金会公司在实验计划的设计和实施方面的合作中受益匪浅。研究项目团队由本科生非博士授牌机构拉斐特学院的教职员工和学生以及Geopier基金会公司的工程师组成。该项目每年将资助两名本科生。另外两名学生将通过拉斐特学院-S优秀学者计划获得资助，该计划支持优秀学生和教师之间的合作研究。研究小组还将与宾夕法尼亚州STEM倡议和宾夕法尼亚州伊斯顿地区学区的一名丰富/有天赋的支持专家和教师合作开展几个外展项目。通过这些活动形成的伙伴关系支持宾夕法尼亚州-S STEM倡议，以大幅增加P-20学生(特别是女性、少数族裔和代表不足的学生)在科学、技术、工程和数学职业中的人数。该项目团队将与PA STEM东北地区网络合作，与几所K-12地区学校的学生和教师合作(总共约4000名学生)。具体地说，参加年度研讨会和项目带头？让学生参加高中工程预科课程和女青年会？S？科技回旋？通过发展计算技能来增强中学女生能力的计划将使学生和他们的老师面临与设计在贫瘠土壤上支撑的结构相关的挑战。通过专业委员会的工作和服务、会议报告、期刊论文和参加CMMI年度会议，PIs和学生将在国内和国际上传播这项研究工作产生的数据、方法和工具。

This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5).Permeable granular piles (i.e., sand compaction piles, stone columns and rammed aggregate piers) are commonly used to support structures and highway facilities constructed on soft or loose soils subjected to static and seismic loading. Although the use of permeable granular piles increases the time rate of consolidation, reduces liquefaction potential, improves bearing capacity and stability, and reduces settlement of poor soils, these piles have a low stiffness and strength that depend on the properties of surrounding soil. Therefore, granular piles have limited use in very soft clays and silts, and in organic and peat soils. This research focuses on developing a new ground improvement alternative using pervious concrete piles to provide high permeability coupled with high stiffness and strength that are independent of surrounding soil properties.When compared to the properties of granular piles, pervious concrete materials provide comparable permeability, more than ten times the strength, and an increase of two orders of magnitude in modulus. The higher elastic modulus and strength of pervious concrete improves the load transfer and load-carrying capacity of the piles without compromising the benefits of high permeability. Using pervious concrete material will ultimately result in reducing the required area replacement ratio, which will significantly reduce construction time and cost. Pervious concrete piles, which have strength and stiffness properties that do not depend on confinement provided by surrounding soil, will provide an effective ground improvement method for very soft clays and silts, and in organic and peat soils. In addition, pervious concrete piles can be reinforced with longitudinal corrosion-resistant steel rebars to improve their ductility and performance when subjected to seismic loading.The research objectives focus on developing pervious concrete mixtures for ground improvement applications and on experimentally characterizing the effects of several construction procedures on soil and pile properties and on soil-pile interaction. Small-scale laboratory experiments using instrumentation and advanced sensors are designed to understand the effects of installation procedures on the behavior of single pervious concrete piles and groups of pervious concrete piles subjected to vertical, uplift, lateral,and embankment loading conditions. The analytical work focuses on developing computational models that accurately predict the behavior of pervious concrete pile systems through three stages: pile installation, consolidation, and in-service loading. The analytical models will be calibrated using the results of the laboratory material and pile load tests and both sophisticated analytical methodologies for use by researchers and simplified analytical tools recommended for practicing engineers will be developed. The Soil-Structure Interaction Facility at Lafayette College, which was recently funded by the National Science Foundation?s Major Research Instrumentation Program, will be used to conduct the experimental and analytical studies. The research will benefit significantly from the collaboration of the Geopier Foundation Company in the design and conduction of the experimental program. The research project team consists of faculty and students from Lafayette College, which is an undergraduate non-Ph.D. granting institution, and engineers from Geopier Foundation Company. Two undergraduate students will be funded by the project each year. Two additional students will be funded through Lafayette College?s EXCEL Scholars Program, which supports collaborative research between high-performing students and faculty. The research team will also collaborate with the Pennsylvania STEM Initiative and an enrichment/gifted support specialist and teacher from the Easton Area School District, PA, in several outreach programs. The partnerships formed through these activities support the Pennsylvania?s STEM Initiative to dramatically increasing the number of P-20 students (especially females, minorities and the underrepresented) in Science, Technology, Engineering and Mathematics careers. The project team, in collaboration with the Northeast Regional Network of PA STEM, will work with students and teachers in several area K-12 schools (total ~4000 students). Specifically, participating in yearly workshops and ?Project Lead the Way? that engage students in high school pre-engineering programs and the YWCA?s ?Tech Gyrl? program that empowers middle school girls by developing computing skills will expose students and their teachers to the challenges associated with designing structures supported on poor soils. Through professional committee work and service, conference presentations, journal papers, and participating in the CMMI annual meeting; the PIs and students will disseminate the data, methods, and tools produced by this research effort nationally and internationally.