Abstract
The accuracy of numerical simulations for unsaturated seepage through rock slopes, caused by rainfall, may be considerably reduced if the unsaturated permeability of rock pores is not considered. A dual-continuum model was adopted in this study to analyze the influence of rainfall infiltration on the stability of fractured-rock slopes. A simple two-dimensional slope model was established to simulate the four cases that may occur in the infiltration boundary of these two domains under four types of rainfall intensity. Then, taking the rock slope of the Fushun West open-pit mine (eastern China) as an example, the rainfall infiltration laws and slope stability were investigated based on both the equivalent continuum model and dual-continuum model under three rainfall patterns: equal intensity, single-peak intensity, and double-peak intensity. In the dual-continuum model, the infiltration depth was much larger than that in the equivalent continuum model because of the preferential flow. Moreover, the infiltration and water exchange in the upper and middle (near the water table) parts of the slope were comparatively analyzed. The strength reduction method and the local safety factor method were used to reveal that the preferential flow can greatly reduce the stability of the fractured-rock slope.
Résumé
La précision des simulations numériques pour l’infiltration non saturée à travers des pentes rocheuses, causée par des précipitations, peut être considérablement réduite si la perméabilité non saturée des pores de la roche n’est. pas prise en compte. Un modèle à double continuum a été adopté dans cette étude pour analyser l’influence de l’infiltration des précipitations sur la stabilité des pentes rocheuses fracturées. Un modèle simple de pente bidimensionnelle a été établi pour simuler les quatre cas qui peuvent se produire dans les conditions limites d’infiltration de ces deux domaines pour quatre types d’intensité de pluie. Ensuite, en prenant l’exemple de la pente rocheuse de la mine à ciel ouvert de Fushun West (Chine orientale), les lois d’infiltration des précipitations et la stabilité de la pente ont été étudiées sur la base du modèle de continuum équivalent et du modèle à double continuum pour trois types de précipitations: intensité égale, intensité à pic unique et intensité à double pics. Dans le modèle à double continuum, la profondeur d’infiltration était beaucoup plus importante que dans le modèle à continuum équivalent en raison de l’écoulement préférentiel. En outre, l’infiltration et l’échange d’eau dans les parties supérieure et moyenne (près de la nappe phréatique) de la pente ont été analysés de manière comparative. La méthode de réduction de la résistance et la méthode du facteur de sécurité local ont été utilisées révélant que l’écoulement préférentiel peut réduire considérablement la stabilité de la pente rocheuse fracturée.
Resumen
La precisión de las simulaciones numéricas para la infiltración a través de laderas de roca, causada por la precipitación, puede reducirse considerablemente si no se considera la permeabilidad no saturada de los poros de la roca. En este estudio se adoptó un modelo de doble continuidad para analizar la influencia de la infiltración de la precipitación en la estabilidad de las laderas de roca fracturada. Se estableció un modelo simple de ladera bidimensional para simular los cuatro casos que pueden ocurrir en el límite de infiltración de estos dos dominios bajo cuatro tipos de intensidad de lluvia. A continuación, tomando como ejemplo la ladera rocosa de la mina a cielo abierto de Fushun West (este de China), se investigaron las leyes de infiltración de las precipitaciones y la estabilidad de las laderas basándose en el modelo continuo equivalente y en el modelo de doble continuidad bajo tres patrones de precipitación: intensidad igual, intensidad de un solo pico e intensidad de dos picos. En el modelo de doble continuidad, la profundidad de infiltración era mucho mayor que en el modelo continuo equivalente debido al flujo preferente. Además, se analizaron comparativamente la infiltración y el intercambio de agua en las partes superior y media (cerca del nivel freático) de la ladera. El método de reducción de la resistencia y el método del factor de seguridad local se utilizaron para revelar que el flujo preferencial puede reducir en gran medida la estabilidad de la ladera de roca fracturada.
摘要
如果不考虑岩石孔隙的非饱和渗透率, 降雨引起的岩质边坡非饱和渗流数值模拟的准确性会大大降低。本研究采用双重介质模型分析降雨入渗对裂隙岩质边坡稳定性的影响。建立简单的二维坡面模型, 模拟四种降雨强度下这两个区域入渗边界可能出现的四种情况。然后, 以中国东部抚顺西露天矿岩质边坡为例, 基于等效介质模型和双重介质模型研究了等强度、单峰强度和双峰强度的三种降雨模式下的降雨入渗规律和边坡稳定性。在双重介质模型中, 由于优先流, 入渗深度远大于等效介质模型。此外, 对斜坡上、中(靠近地下水位)部分的入渗和交换水量进行了对比分析。采用强度折减法和局部安全系数法揭示优先流会大大降低裂隙岩质边坡的稳定性。
Resumo
A acurácia de modelos numéricos para infiltração na zona não saturada de taludes rochosos, causada por chuvas, pode ser consideravelmente reduzida se a permeabilidade insaturada dos poros rochosos não é considerada. Para este estudo, um modelo de dupla porosidade foi adotado para analisar a influência da infiltração da água da chuva na estabilidade de encostas de rochas fraturadas. Foi estabelecido um modelo de talude bidimensional simples para simular os quatro casos que podem ocorrer em bordas de infiltração desses dois domínios sobre quatro tipos de intensidade de pluviosidade. Depois, utilizando o talude rochoso da mina à céu aberto do Oeste de Fushun (leste da China) como exemplo, as leis de infiltração de chuvas e de estabilidade de taludes foram investigadas baseando-se tanto em modelo contínuo equivalente quanto de dupla porosidade sob três padrões de chuvas: mesma intensidade, intensidade de pico único, e dois picos de intensidade. No modelo de dupla porosidade, a profundidade de infiltração foi muito maior que no modelo equivalente contínuo por conta do fluxo preferencial. Ademais, a infiltração e troca de água nas porções superiores e intermediárias (próximo ao nível d’água) do talude foram analisadas comparativamente. Os métodos de redução de tensão e de fator de segurança local foram usados para revelar que o fluxo preferencial pode reduzir muito a estabilidade de taludes de rochas fraturadas.
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The authors would like to thank the reviewers for their useful comments.
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This work was supported by National Key Research and Development Program of China (No. 2016YFC0801602) and the National Natural Science Foundation of China (52074292).
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Nian, G., Chen, Z., Bao, M. et al. Rainfall infiltration boundary conditions and stability of a fractured-rock slope based on a dual-continuum model. Hydrogeol J 30, 829–847 (2022). https://doi.org/10.1007/s10040-022-02468-7
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DOI: https://doi.org/10.1007/s10040-022-02468-7