Abstract Most natural rock slope failures result from long-term strength degradation. It is often hypothesized that glacial retreat leads to enhanced progressive damage accumulation in adjacent rock slopes, due to mechanical unloading and changes to the thermal and hydraulic boundary conditions. However, direct observations of subsurface processes in a rock slope subject to glacial retreat are rare. In this paper, we present the design, implementation, and performance of a new borehole monitoring system installed on a rock slope in fractured crystalline rock located beside the glacier tongue of the retreating Great Aletsch Glacier (Valais, Switzerland). The three vertical, 50 m deep boreholes were instrumented to continuously monitor groundwater pressure, temperature and deformation at high resolution, in order to investigate thermo-hydro-mechanical coupled slope processes that drive progressive rock mass damage. We show that the system is capable of measuring both reversible and irreversible displacements along single fractures at magnitudes ranging between 0.001 mm to >2 mm in the studied rock slope, and that it is often possible to identify drivers of these deformation signals. The transient subsurface temperature field shows clear indications of former ice occupation in form of cold temperatures preserved at depth and superimposed annual temperature cycles penetrating down to a depth of about 17 m. The variability of the pressure head in the slope is driven by annual snowmelt infiltration cycles, rainfall events, and the assumed connection to englacial water of the temperate glacier. The new and continuously growing dataset presented here will enable us to relate the changing boundary conditions caused by glacial retreat and fatigue from daily to annual thermal and hydraulic loading cycles to progressive rock mass weakening, which may ultimately result in rock slope failure.

中文翻译：

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紧邻积极后退冰川的热-水-机械岩石边坡过程的钻孔监测

摘要 大多数天然岩质边坡破坏是由于长期强度退化造成的。通常假设，由于机械卸载以及热力和水力边界条件的变化，冰川退缩会导致相邻岩石边坡的渐进性损伤积累增强。然而，对受冰川退缩影响的岩石斜坡的地下过程的直接观察很少见。在本文中，我们介绍了安装在位于退缩的大阿莱奇冰川（瑞士瓦莱州）的冰川舌旁的裂隙结晶岩中的岩石斜坡上的新型钻孔监测系统的设计、实施和性能。三个 50 m 深的垂直钻孔被安装在仪器上，以高分辨率连续监测地下水压力、温度和变形，为了研究驱动渐进式岩体损坏的热-水-机械耦合边坡过程。我们表明，该系统能够测量所研究的岩石斜坡中沿单个裂缝的可逆和不可逆位移，幅度在 0.001 毫米到 >2 毫米之间，并且通常可以识别这些变形信号的驱动因素。瞬态地下温度场显示了以前冰占据的清晰迹象，以保持在深处的低温和叠加的年温度循环的形式向下渗透到约 17 m 的深度。斜坡中压力水头的变化是由每年的融雪渗透循环、降雨事件以及与温带冰川的冰川水的假设联系驱动的。