Surface thermal response and mechanical property changes of weathered sandstone rock-hewn cave temples:implication for the evaluation of surface weathering(deterioration)
Surface thermal response and mechanical property changes of weathered sandstone rock-hewn cave temples:implication for the evaluation of surface weathering(deterioration)
Near-surface weathering is a crucial problem threatening the preservation of rock-hewn cave temples.Erosion pattern evaluation and risk assessment through property variation of the weathered surface is a vital point that needs to be addressed for preventive conservation.In this study,we used portable non-destructive testing instruments(ProceqEquotip 550 Leeb hardness tester,FLIR T660 infrared thermal camera)to measure surface hardness and to monitor the surface temperature of 8 studied surfaces on the facade of the North Grotto Temple in Qingyang,Gansu Province.Based on the in-situ measurement,we studied the thermal response and property changes of the typical weathering patterns.The study results show that different weathering patterns could directionally affect the magnitude of surface hardness and the range of temperature fluctuation to some extent.The diurnal temperature of the crust surface fluctuated within a minor degree,and the surface hardness was broadly dispersed at a high range of value.The diurnal temperature fluctuations of the powdering surface and salt efflorescence surface were relatively gentle and flattened,and their surface hardness values were centralized at a low level.The diurnal temperature fluctuation of the groove-like erosion(differential weathering)surface was slightly greater than that of surfaces with powdering and salt efflorescence,and the surface hardness was centralized at a higher level.Surfaces covered with microorganisms had the most extensive range of diurnal temperature fluctuation,and scattered surface hardness values were distributed at a low level.Given the above evidence,the relationship between weathering patterns and properties can not only help with the distinguishing of distribution and developmental trends of weathering patterns in daily monitoring but also has an indicative effect on the risk warning of rock-hewn cave temples.
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