为观测和分析T-bar循环贯入过程中被困空腔对软黏土流动特性的影响,利用Laponite RD、焦磷酸钠和去离子水配制透明黏土,自制由加载设备、CCD相机、激光器和控制系统组成的T-bar循环贯入试验装置,开展T-bar在透明黏土中的循环贯入试验。结果表明:T-bar初次贯入过程中,被困空腔影响土体绕探头的流动,土体不能进入全流动状态;T-bar初次上拔过程中,被困空腔与探头发生脱离,悬浮于探头上方,对土体流动的影响逐渐减弱,T-bar上拔2倍探头直径深度时土体流动不再受被困空腔影响,进入到全流动状态;第2—第10次循环贯入过程中,被困空腔稳定悬浮于土中,不影响土体流动,T-bar贯入1倍探头直径深度时土体流动表现为全流动状态;被困空腔对于T-bar循环贯入测试结果无显著影响,在T-bar初次贯入被困空腔阶段下通过T-bar循环贯入测试软黏土重塑强度是合理的。
Abstract
To observe and analyze the impact of trapped cavities on the flow dynamics of soft clay during cyclic T-bar penetration, we prepared transparent clay using Laponite RD, sodium pyrophosphate, and deionized water, and constructed a cyclic T-bar penetration testing apparatus comprising loading equipment, a CCD camera, a laser, and a control system. By using this test apparatus, we conducted cyclic T-bar penetration test on the transparent clay to investigate the influence of trapped cavities on the flow characteristics of soil. The findings reveal that trapped cavities impeded soil flow around the probe during initial T-bar penetration, preventing it from attaining a full-flow state. As the T-bar was initially extracted, the trapped cavities disengaged from the probe and remained suspended above it, gradually diminishing its effect on soil flow. By the time the T-bar was extracted to a depth twice the probe diameter, the soil flow was unaffected by the trapped cavity and achieved a full-flow state. Throughout the 2nd to the 10th cycle penetrations, trapped cavities remained stably suspended in the soil, without impeding soil flow. When the penetration depth was equivalent to one time the probe diameter, the soil reached full-flow state. In conclusion, trapped cavities exert no significant impact on the outcomes of cyclic T-bar penetration test. Hence, it is rational to test the remolded shear strength of soft clay using cyclic T-bar penetration during the initial penetration through trapped cavities.
关键词
透明黏土 /
T-bar /
循环贯入试验 /
被困空腔 /
流动特性
Key words
transparent clay /
T-bar /
cyclic penetration test /
trapped cavity /
flow characteristics
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基金
国家自然科学基金项目(5189093,51879183);河北省高等学校科学技术青年基金项目(QN2018089)
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