Abstract:
Wuzhou City is the distribution area of the granite weathering crust with huge thickness in South China. It is selected as the study area. The study aims to establish a systematic,scientific,and operable standard for the vertical division of granite weathering crust. On the basis of field investigation,drilling,in-situ test,laboratory test,and comprehensive research,an index system of qualitative and quantitative composite judgment is established. The vertical zoning and engineering geological characteristics of granite weathering crust in Wuzhou City are studied. The studies show that: (1) Granularity analysis can be used as one of the methods of vertical zoning of granite weathering crust. The division results are in good agreement with the results of the in-situ test division. (2) Clay,silt and sand soil account for the largest proportion in residual soil zone,completely weathered zone and strongly weathered zone,respectively. The size of soil particles increases with increasing depth. The proportion of gravel and sand particles with relatively large particle sizes gradually increases. The proportion of powder and clay particles with relatively small particle sizes gradually decreases. Particle size 0.05mm is the boundary of curve intersection of residual soil,fully weathering zone and strongly weathering zone. The percentage of soil content at this place is approximately equal,revealing that the value of 0.05mm particle size is one of the important indicators for the vertical division of granite weathering crust. (3) With the increase of the drilling depth,the number of cone dynamic penetration test hits and the number of standard penetration tests increase simultaneously. The corrected standard penetration number
N and cone dynamic penetration penetration number
N63.5 show a polynomial correlation. In this paper,the standard of vertical zoning of granite weathering crust was established,and the recommended value of the bearing capacity of the granite weathering crust soil is given,which had certain guiding and reference significance for major project construction and selection of engineering geological characteristic parameters in granite distribution area.