Typological analysis of slidequakes emitted from landslides: experiments on an expander body pile and Sobradinho landslide (Brasilia, Brazil)

Abstract Reactivation of a landslide is usually accompanied by microseismic signals emitted from the deforming soil mass. The reproduction of similar signals in a physical model test conducted under control conditions can allow researchers to explore and test such complicated signals to improve the prediction of full-scale failure. The present study investigates the similarity between the slidequakes (microseismicity) naturally emitted from an existing colluvial landslide (Sobradinho, Brazil) in response to rainfalls and the emissions generated by a pullout test of an expander body (EB) pile in tropical soil under controlled conditions. The microseismic signals emitted from both experimental sites (i.e. the landslide and the EB pile test) were recorded and compared. Data were acquired by mini-arrays of four short-period seismometers. For the signal nomenclature, a typological scheme was adopted, in which sonograms/spectral contents of the signals were used. As a result, short duration microseismic signals were observed during the pullout test. In contrast, at the Sobradinho landslide, the testing detected signals of different characteristics whose source mechanisms have remained ambiguous, mainly because of the short duration of the data campaigns. However, at the landslide, propagating events were observed that might be attributed to the energies generated by the river bedload during the heavy rains. The present study offers some insight into the pre-collapse dynamic behavior of unstable slopes in clayey formations.

摘要：滑坡复活过程通常伴随变形土体辐射出的微地震信号。在可控条件下开展物理模型试验复现同类信号，可助力研究者探究并解析这类复杂信号，进而提升全尺度滑坡失稳的预测能力。本研究针对巴西索布拉迪尼奥（Sobradinho）现有崩积层滑坡因降雨触发产生的天然滑震（slidequakes，微地震活动），与受控条件下热带土体中扩体桩（Expander Body, EB）拉拔试验产生的微地震信号之间的相似性展开了系统性探究。本研究对两处试验现场（即滑坡现场与扩体桩拉拔试验现场）辐射的微地震信号进行了采集记录与对比分析，信号采集采用由4台短周期地震仪组成的微型阵列。在信号命名规则上，本研究采用了以信号声谱图/频谱特征为依据的分类体系。试验结果显示，扩体桩拉拔试验过程中观测到了短时域微地震信号。与之相对，索布拉迪尼奥滑坡现场检测到的信号特征各异，其震源机制仍不明确，这主要源于本次数据采集活动的周期较短。不过，滑坡现场观测到了传播性地震事件，这类事件或可归因于强降雨期间河床推移质运动所产生的能量。本研究为黏质地层不稳定斜坡失稳前的动力行为提供了新的认知视角。