Top and base California bearing ratio behaviour of soaked gypsum-rich roadbed soils

摘要

The effect of long-term soaking on the California bearing ratio (CBR) of the top (CBR_T) and base (CBR_B) of both gypsum sand and clayey gypsiferous soil was obtained. The gypsum contents of gypsum sand and clay were about 28·9% and 25·6%, respectively. For each soil, CBR specimens were compacted at optimum moisture content and 95% of the modified American Association of State Highway and Transportation Officials (AASHTO) maximum dry density. For each soil, two specimens were soaked for periods of 0, 4, 7, 15, 30, 60, 120 and 180 d with 50 lb (222·5 N) surcharge load. For each soil specimen, the CBR load-penetration test was carried out at the top (during soaking) and the inverted bottom (base) of the specimen, yielding CBR_T and CBR_B, respectively. The paper reveals that there is a significant drop in CBR_T and CBR_B with increasing soaking period. This effect is more pronounced in CBR_T than CBR_B for both soils. There is a strong correlation between CBR_T and CBR_B for each soil tested and the difference between CBR_T and CBR_B increases with increasing soaking period.