Research purposes: For fracture grouting mode or compaction grouting mode in sand layer, compaction behavior of sand occurs currently. Improvement degree of performance of compacted sand has a marked effect on macroscopical performance of grouted body. Cohesive strength, internal friction angle and permeability coefficient are used as performance indexes of compaction reinforcing effect. With clayey sand layer in Qingdao district as the typical medium, the growth of sand properties with compaction degree under different clay contents was tested, and the quantitative relationship between compaction reinforcing effect and grouting pressure was acquired. At the same time, the effect of clay content on the performance improvement of compacted sand layer was analyzed. Finally, the evaluation index was put forward to evaluate whether sand layer can be effectively reinforced by compaction method, which was characterized by critical clay content.
Research conclusions: (1) Grouting compaction can significantly improve various performance indexes of sand layer. Under laboratory test condition, cohesive strength has risen by 30.8~87.6 kPa, internal friction angle has risen by 13~15°, and permeability coefficient has decreased by 2~5 order of magnitude. (2) The performance improvement of the compacted sand layer is positively correlated with clay content. When clay content less than critical clay content, sand layer can not be effectively reinforced by compaction method. (3) The research results can be applied to the field of grouting reinforcement in tunnel engineering through sand layer, and can be used to guide grouting design.
Key words
sand /
grouting /
compaction /
reinforcement effect /
reinforcement efficiency
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Footnotes
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