Upgrading the National Geotechnical Centrifuge

这一行动是为建造国家土工离心机的围栏提供资金。离心机模型是研究各种岩土地震工程问题的有用工具。土结构中的应力和应变状态取决于覆盖层压力，这类似于水体中随深度增加的静水压力。这种覆岩压力是重力作用的结果。当测试地球结构的比例模型时，这种重力载荷必须被正确地定标，这要求重力与模型比例的减小成比例地增加：一个半比例的模型必须承受正常重力载荷的两倍。重力载荷的增加可以通过在离心机中测试缩尺模型来实现。国家土工离心机是由NASA Ames捐赠给加州大学戴维斯分校的。它已经被改装成岩土工程离心机，最近被转移到戴维斯校园。它现在已经在新的地点投入使用，但没有资金为围栏提供屋顶。因此，离心机在露天运行，这严重限制了机器的能力，因为风量损失：当手臂转动时，它就像一个大型离心风机。这些风损失是不可避免的，但通过适当的外壳设计可以显著减少这些损失。对于国家土工离心机，通过安装设计合理的围护结构，露天矿的安装性能可以从100g吨提高到500g吨。性能的提高提供了美国迫切需要的能力。需要这种能力的研究人员目前必须在英国剑桥的离心机上进行测试。这既昂贵又缓慢。建造国家土工离心机的外壳将提供一个设施，大大增加可以在岩土工程，特别是地震工程中进行的实验。

This action is to provide funds for the construction of an enclosure to the National Geotechnical Centrifuge. Centrifuge modeling is a useful tool for studying a wide variety of geotechnical earthquake engineering problems. The state of stress and strain in an earth structure is dependent upon the overburden pressure, which is analogous to the hydrostatic pressure which increases with depth in a body of water. This overburden pressure is a result of gravitational loading. When testing a scale model of an earth structure, this gravitational loading must be correctly scaled, and this requires that gravity be increased in proportion to the reduction in the scale of the model: a half-scale model has to be subjected to twice the normal gravity loading. This increase in gravity loading can be obtained by testing the scale model in a centrifuge. The National Geotechnical Centrifuge was donated by NASA AMES to the University of California at Davis. It has been converted for use as a geotechnical engineering centrifuge, and more recently it was moved to the Davis campus. It is now operational at the new location, but funds were not available to provide a roof for the enclosure. As a result, the centrifuge is operating in the open air, which severely limits the capacity of the machine due to windage losses: as the arm turns it acts as a large centrifugal fan. These windage losses are unavoidable, but they can be reduced significantly by appropriate design of the enclosure. For the National Geotechnical Centrifuge, the open pit installation performance can be increased from 100 g-tons to 500 g-tons by installing a suitably designed enclosure. The increased performance provides a capacity which is sorely needed in the United States. Researchers needing this capacity must currently perform their tests on a centrifuge in Cambridge, England. This is both costly and slow. The construction of an enclosure for the National Geotechnical Centrifuge will provide a facility that will increase dramatically the experiments that can be performed in geotechnical engineering, in particular in earthquake engineering.