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首页> 外文期刊>Geotechnical testing journal >A System to Measure Volume Change of Unsaturated Soils in Undrained Cyclic Triaxial Tests
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A System to Measure Volume Change of Unsaturated Soils in Undrained Cyclic Triaxial Tests

机译：不排水三轴试验中不饱和土壤体积变化的测量系统

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It is common to employ a traditional double cell system, of which an open-ended inner cell is installed in an ordinary triaxial apparatus, to measure the volume change of unsaturated specimens. In such a system, the total apparent volumetric strain of the specimen (epsilon(v)) is deduced from the water level change in the inner cell, monitored by a differential pressure transducer (DPT) considering, meanwhile, the top cap intrusion into the inner cell recorded by a vertical displacement transducer (VDT). Severe apparent volumetric strain, caused by the compliance of the double cell system(epsilon(v,SC)), was observed during the undrained cyclic loading tests in a previous study. Test results on a steel-spring dummy specimen revealed that epsilon(v,SC) was induced not only by such as the meniscus effect, but unexpectedly also by the asynchronous responses between the DPT and the VDT (i.e., the response of the DPT was delayed compared with that of the VDT). By doing some treatment epsilon(v,SC) could be reduced to some extent, whereas the magnitude of epsilon(v,SC) was still too high to be acceptable when the tested specimen approached the liquefied state. To radically solve these technical difficulties, a modified double cell system, named the linkage double cell system, was developed in this study. In this modified system, a linkage rod moving simultaneously with the loading shaft was introduced, through which the DPT could directly measure epsilon(v) without considering the top cap or loading shaft intrusion. Test results for the steel-spring dummy specimen as well as for saturated and unsaturated soil specimens demonstrated that the linkage double cell system has major advantages in measuring accurately the volume change of the specimen during undrained cyclic triaxial loading tests compared with the traditional double cell system.
机译：通常采用传统的双池系统，其中在常规三轴设备中安装了一个开放式内部池，以测量不饱和试样的体积变化。在这样的系统中，样本的总表观体积应变（ε（v））由内部单元中的水位变化推导出来，并由压差传感器（DPT）进行监控，同时考虑到顶盖侵入到垂直位移传感器（VDT）记录内部细胞。在先前的研究中，在不排水的循环载荷测试中观察到由双细胞系统的顺应性引起的严重的表观体积应变（ε（v，SC））。在钢制弹簧假试样上的测试结果表明，ε（v，SC）不仅是由弯液面效应引起的，而且出乎意料的是由DPT和VDT之间的异步响应引起的（即DPT的响应为与VDT相比有所延迟）。通过做一些处理，ε（v，SC）可以降低到一定程度，而当被测样品接近液化状态时，ε（v，SC）的大小仍然过高而不能接受。为了从根本上解决这些技术难题，本研究开发了一种改进的双电池系统，称为联动双电池系统。在这种改进的系统中，引入了与加载轴同时运动的连杆，通过该连杆，DPT可以直接测量ε（v），而无需考虑顶盖或加载轴的侵入。钢弹簧虚拟样本以及饱和和不饱和土壤样本的测试结果表明，与传统的双单元系统相比，联动双单元系统在不排水的循环三轴载荷测试过程中具有准确测量样本体积变化的主要优势。 。

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