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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Bank undercutting and tension failure by groundwater seepage: predicting failure mechanisms
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Bank undercutting and tension failure by groundwater seepage: predicting failure mechanisms

机译：地下水渗漏引起的河床咬蚀和张拉破坏：预测破坏机制

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摘要

Groundwater seepage can lead to the erosion and failure of streambanks and hillslopes. Two groundwater instability mechanisms include (i) tension failure due to the seepage force exceeding the soil shear strength or (ii) undercutting by seepage erosion and eventual mass failure. Previous research on these mechanisms has been limited to non-cohesive and low cohesion soils. This study utilized a constant-head, seepage soil box packed with more cohesive (6% and 15% clay) sandy loam soils at prescribed bulk densities (1.30 to 1.70Mgm~(-3)) and with a bank angle of 90° to investigate the controls on failure mechanisms due to seepage forces. A dimensionless seepage mechanism (SM) number was derived and evaluated based on the ratio of resistive cohesion forces to the driving forces leading to instability including seepage gradients with an assumed steady-state seepage angle. Tension failures and undercutting were both observed dependent primarily on the saturated hydraulic conductivity, effective cohesion, and seepage gradient. Also, shapes of seepage undercuts for these more cohesive soils were wider and less deep compared to undercuts in sand and loamy sand soils. Direct shear tests were used to quantify the geotechnical properties of the soils packed at the various bulk densities. The SM number reasonably predicted the seepage failure mechanism (tension failure versus undercutting) based on the geotechnical properties and assumed steady-state seepage gradients of the physical-scale laboratory experiments, with some uncertainty due to measurement of geotechnical parameters, assumed seepage gradient direction, and the expected width of the failure block. It is hypothesized that the SM number can be used to evaluate seepage failure mechanisms when a streambank or hillslope experiences steady-state seepage forces. When prevalent, seepage gradient forces should be considered when analyzing bank stability, and therefore should be incorporated into commonly used stability models. Copyright ? 2013 John Wiley & Sons, Ltd.
机译：地下水的渗漏会导致河岸和山坡的侵蚀和破坏。两种地下水失稳机制包括：（i）由于渗流力超过土壤抗剪强度而引起的拉力破坏，或者（ii）因渗流侵蚀而发生的咬陷和最终的质量破坏。以前对这些机制的研究仅限于非粘性和低粘性土壤。这项研究使用了一个恒定水头的渗流土箱，在规定的堆积密度（1.30至1.70Mgm〜（-3））下，以90°的倾斜角填充了更多粘性（6％和15％粘土）的砂壤土。研究由于渗流力引起的破坏机制的控制措施。基于阻力凝聚力与导致不稳定性的驱动力之比，得出无量纲的渗漏机制（SM）数，并采用假定的稳态渗流角进行渗流梯度评估。观察到拉伸破坏和咬边都主要取决于饱和的水力传导率，有效的内聚力和渗透梯度。而且，与沙土和壤质沙土中的底切相比，这些更具粘性的土壤的底切形状更宽，深度更小。使用直接剪切试验来量化以各种堆积密度填充的土壤的岩土特性。 SM值基于岩土特性和物理规模实验室实验的稳态渗流梯度，合理地预测了渗流破坏机理（张力破坏与底切），但由于岩土参数的测量，假定的渗流梯度方向而存在一些不确定性，以及故障块的预期宽度。假设当水库或山坡遇到稳态渗流力时，SM数可用于评估渗流破坏机理。当普遍存在时，在分析堤岸稳定性时应考虑渗透梯度力，因此应将其纳入常用的稳定性模型中。版权？ 2013 John Wiley＆Sons，Ltd.

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