Canadian Geotechnical Journal, Ahead of Print.
Understanding triggering mechanisms of slope failure is of great importance to the stability analysis and safety warning of waste landfill. This paper presents a centrifuge model test on slope failure induced by elevated gas pressure in wet landfill. The formation process of liquid level and gas pressure in the landfill is simulated by means of liquid and gas injections under a centrifugal acceleration of 66.7 g. The injected liquid contains surfactants, which allow it to generate foam in the waste pores when mixed with the injected gas. The pore gas and liquid pressures under two-phase flow condition are monitored separately to clarify the instability process. It is found that the continuous gas injection makes the pore gas pressure increase to peak values of 83.0 kPa–100.8 kPa, which are higher than the peak liquid pressures of 61.3 kPa–75.6 kPa. The formation of high gas pressure zone is attributed to the low gas permeability, which is affected by high liquid saturation as well as foam generation. The slope failure occurs when the pore gas pressure increases to the peak value and the corresponding shear strength decreases to the critical value. Although the gas injection raises the liquid level, the factor of safety of landfill slope will be overestimated if only considering the effect of liquid pressure. According to the response curves of displacement to gas pressure rise, the critical ratios of gas pressure to earth pressure are determined to be 0.74–0.84, which fall within the range of the prototype landfill. The difference between foam and air on pore pressure distribution is also calculated and discussed.

中文翻译：

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湿式城市固体垃圾填埋场气体压力升高引起边坡失稳的离心机模型

加拿大岩土工程杂志，印刷前。
了解边坡失稳的触发机制对于垃圾填埋场的稳定性分析和安全预警具有重要意义。本文提出了湿式垃圾填埋场气体压力升高引起的边坡破坏的离心模型试验。通过在66.7 g离心加速度下注液和注气的方式模拟垃圾填埋场液位和气压的形成过程。注入的液体含有表面活性剂，当与注入的气体混合时，可以在废孔中产生泡沫。分别监测两相流条件下的孔隙气体和液体压力，以阐明不稳定过程。结果发现，连续注气使孔隙气体压力增加至峰值83.0 kPa~100.8 kPa，高于峰值液体压力61.3 kPa~75.6 kPa。高气压区的形成归因于低气体渗透率，这受到高液体饱和度以及泡沫产生的影响。当孔隙气体压力增加到峰值并且相应的抗剪强度降低到临界值时，边坡就会发生破坏。虽然注气提高了液位，但如果仅考虑液体压力的影响，则会高估填埋场边坡的安全系数。根据位移对瓦斯压力上升的响应曲线，确定瓦斯压力与土压力的临界比值为0.74~0.84，落在原型填埋场的范围内。还计算并讨论了泡沫和空气对孔隙压力分布的差异。