| Tuff has the characteristics of fissure development and sharp decrease of strength parameter after water metamorphism.Tuff slopes with different degree of weathering shows different characteristics of rock mass and different failure mechanisms.At present,the related research is few.This paper relies on the Huizhou-Shenzhen Expressway Widening and extension project,we select several typical tuff high slopes with different degree of weathering to carry out the research on failure mechanism,stability and reinforcement technology of tuff high slopes,and has achieved the following results:1.Through field investigation,the geometric size and rock mass characteristics of the slopes along the project are statistically analyzed,grasped the basic information like Stratigraphic lithology,slope shape,slope rate,strengthening means of four typical different degree of weathering tuff high slopes.2.Combining with the relevant research data,the common failure mode of rock high slope is expounded,and the influencing factors on the stability of tuff high slopes are analyzed.Combining with the on-site practice of typical tuff high slope,the failure mechanism is explored,and the main failure mechanism is “sliding-fracture” failure and “slip” failure.3.By using numerical calculation technology,the safety coefficient,surface displacement,the bolt load changes of tuff high slopes with different weathering degree in various stages of construction under the normal condition and rainfall condition is studied,the results show that during the construction period,only one high slope consist of strongly~fully weathered tuff was in a state of under stable condition,and all high slopes were in stable state after the construction was completed.The maximum displacement area of two tuff high slopes with low weathering degree is located in the three or four grade slope,the maximum anchor load area is located in the two or three grade slope.The maximum displacement area of two tuff high slopes with high weathering degree is located in the grade two or four grade slope,and the maximum anchor load area is located in the two or three grade slope.The higher the weathering degree is,the greater the influence of rainfall is on the stability of the slopes.4.Combined with the field monitoring results,the displacement,the stress characteristics of the bolt and the disease situation of four typical tuff high slope during the monitoring is analyzed.The results show that two high slopes consist of middle~strongly weathered,micro~middle weathered tuff only appear some disease about bolt load increased significantly and the lattice beam cracked slightly during construction,their stability is good;two high slopes consist of strongly~fully weathered tuff appear significant growth of local slide and anchor load,the sudden increase of displacement monitoring points and other diseases,their stability is poor.5.Based on the numerical calculation results and field monitoring results,the slope displacement and anchor load obtained by the two methods are compared and analyzed.We point out the most dangerous area of each typical high slope.6.By selecting the commonly used anchorage techniques of high rock slope,optimize the design from anchor length,anchor angle,and combined support of anchor and anchor cable by numerical calculation method,put forward the anchorage parameter values and engineering suggestions for tuff high slope. |
