Abstract: Tuff is softened and disintegrated when contacts with water, resulting in remarkable strength decline. Tuff high slope in construction are prone to cracking and slippery collapses. In order to solve the stability problem in the secondary excavation of the high tuff slope of Huizhou-Shenzhen highway Project, we analyzed the instability mechanism and influencing factors in the excavation of high tuff slope using finite element software, and put forward reinforcement technology for the secondary excavation. Moreover, we assessed the result of reinforcement by joint monitoring of slope displacement and support structure stress. Results unveiled that the excavation-induced unloading deformation was the major cause, and rainfall the inducing factor of the first shallow slide of grade-3 slope to grade-5 slope; the absence of timely support was the major cause, and still rainfall the inducing factor of the secondary collapse after the square cutting and unloading. We propose to apply concrete retaining wall and anchor beam in the collapsed area of grade-3 slope. After the reinforcement construction, the maximum horizontal displacement was 0.28 mm/d at grade-4 platform, averaging only 0.02 mm/d, and the stress of support structure stayed within the early-warning range with no obvious fluctuation, indicating an effective reinforcement.

Key words: tuff high slope, stability analysis, protection technology, numerical simulation, field test, secondary excavation