Abstract: To explore the characteristics and regularity of freeze-thaw weathering of rock mass in the headwaters region of three rivers (Yangtze River, Yellow River, and Lantsang River), we conducted rock slice observation and physical property test. On this basis and in association with scientific field investigation and aerial images, we summarized the characteristics of freeze-thaw weathering, concluded the process of freeze-thaw damage of rock mass, and analyzed the influences of key factors on the freeze-thaw damage process. Here we present the conclusions as follows: 1)the intensity of freeze-thaw weathering declines with the increase or decrease of latitude, weathered rock exposure is more severe with the increase of altitude (with altitude 5000m as an obvious dividing line), rock mass weathering in the north slope (dark side) is weaker than that in the south side (sunny side); 2) the intensity of freeze-thaw weathering of exposed rock mass is different, and the slope form and clastics induced by freeze-thaw weathering differ greatly as for rock mass of different lithological characters; 3)the lithology of rock mass plays an important role in the freeze-thaw weathering. Porosity and pore water are two basic conditions affecting the freeze-thaw weathering process, and the number of freeze-thaw cycles plays a decisive role in the freeze-thaw damage process.

Key words: geotechnical engineering, rock mass, freeze-thaw weathering, key-factor analysis, headwaters region of three rivers