两种失效模式下传感型土工带在砂土中的变形特性研究

Deformational characteristics of sensor-enabled geobelts incorporating two failure modes in reinforced sand

目的:在加筋土结构中的土工带有拉伸断裂和拔出两种失效模式。研究土工带的变形对预测加筋土结构的潜在滑裂面具有重要意义。为了研究在拉伸断裂和拔出这两种不同失效模式下土工带的变形特征,本文在不同法向压力下对不同长度的传感型土工带开展拉拔试验。创新点:1.传感型土工带具有拉敏效应和自检测功能,可以实现土工带在拉伸过程中的应变分布式测量;2.提出了两种失效模式之间的临界线,该临界线考虑了法向压力和筋材有效长度两个参数,可用于筋材失效模式的初步判断;3.根据传感型土工带的变形特征,提出了用于初步预判失效模式的预警准则。方法:1.利用传感型土工带的自检测功能,得到拉拔试验过程中筋材应变的分布情况,并进一步分析得到筋材轴向应力和筋材位移的分布情况;2.根据不同筋材长度和在不同法向压力下的拉拔试验结果,反向拟合得出两种失效模式之间的临界线;3.通过分析传感型土工带的应变、应力和位移分布结果,总结得出两种失效模式下土工带的变形特征。结论:1.提出的两种失效模式之间的临界线考虑了筋材长度和法向压力两种因素,可对筋材失效模式进行初步判断。2.根据传感型土工带分布式检测结果和变形特征,建立了用于判断两种失效模式的预警准则;加筋土结构中的筋材在潜在滑裂面处出现应变峰值,且筋材变形从滑裂面处开始向两侧逐步发展;一旦筋材末端应变不再为零,则筋材易被拔出;若筋材末端应变为零,同时滑裂面处筋材应变极值达到断裂伸长率,则筋材易断裂;该准则可用于判断和识别加筋土结构的潜在失效模式。

Geobelt deformation is of significance when making prejudgments on potential failure planes in reinforced structures.A failure plane results from two geobelt failure modes,tensile failure and pullout.In order to investigate the deformation characteristics of geobelts in two failure modes,results from pullout tests on sensor-enabled geobelts(SEGBs)with various lengths in sand are reported here across a range of normal pressures.Self-measurements of SEGB can provide data during the tests regarding distributions of strain,stress,and displacement.Data collected during pullout tests reveal the effects of normal pressures and specimen lengths on failure mode.A critical line considering normal pressure and specimen length is derived to describe the transition between two failure modes,an approach which can be utilized for preliminary predictions of failure mode in pullout tests.Warning criteria established based on critical line and data from the self-measurements of SEGB are proposed for failure mode prediction which can contribute to prejudgments of potential failure plane in geosynthetically reinforced soil structures.