Mechanical properties and engineering measures of high liquid limit soil

Through labouratory test, the physical and mechanical properties of untreated and 20% sand-treated high liquid limit soil from Yun Luo expressway were studied. Distribution of high liquid limit soil of Guang Dong province in China was drawn. Through field test, the relationship between compaction effort and compaction degree at various water contents was researched. The influence of water content, compaction degree and swelling potential grade on CBR value was analysed. The empirical formulas describing the relationship of CBR value and compaction degree were derived. The test results show that the effective methods to improve high liquid limit soil is to add 20% sand to improve its physical and mechanical properties from economy, technical feasibility and other factors. It is found that CBR value depends on water content, compaction degree and the structural state after soaking expansion. Increasing extent of CBR value with compaction degree of 20% sand-treated high liquid limit soil is more evident compared to untreated soil. The construction standard of high liquid limit soil should consider the influence of the total ratio of swell-shrink besides compaction degree and CBR value. It is concluded that high liquid limit soil can be used as direct filling material of lower embankment by means of necessary measures of wrap-around embankment and reducing the standard of compaction degree while the water content should be controlled between 2% higher and 6% higher than the optimum water content. Only if the compacted water content fall in between 2% lower and 6% higher than optimum water content, 20% sand-treated high liquid limit soil can be used in lower and upper embankment directly.