海南环岛海砂物理力学性质对比研究

COMPARATIVE RESEARCH ON PHYSICAL AND MECHANICAL PROPERTIES OF SEA SAND IN HAINAN

海南岛岛内河砂资源日益匮乏,海砂资源异常丰富,且沿海工程项目主要以海砂地基为主,但至今尚未有针对岛内各海湾海砂物理力学性质的系统研究。本文通过对取自环岛13个海湾代表性海砂土样进行室内土工试验和测试,经物理力学性质指标数据对比分析后发现:岛内海砂含泥量均满足建筑用砂Ⅱ级以上标准;除鱼鳞洲粗砂组级配良好外,其他全部级配不良;东线海湾砂样全部属于中砂和细砂范畴,西线海滩则以粗砂为主;所有砂样均在较小预压荷载(50k Pa)下就能达到密实,半数以上砂样在50~100k Pa的预压荷载下密实度变化较小,而在100~200k Pa的预压荷载下密实度则变化相对较大;不同地区海砂强度指标内摩擦角φ值介于39.24°到48.24°之间,其波动趋势与平均粒径基本一致,波动幅度约为25%,岛内各海湾海砂含盐量差异巨大,最高值金海湾(3.1‰)几乎是最低值清水湾(0.4‰)的八倍;除清水湾外,其他海湾砂样的含盐量均远高于0.6‰的国家标准,若作为工程用砂,必须进行淡化处理。

River sand resource is increasingly scarce compared with dramatic abundance of sea sand resource in Hainan island. Most of coastal engineering projects are sea sand foundation. But so far, there are limited systematically research results on physical and mechanical properties of sea sand in Hainan. This paper deals with a comparative study on physical and mechanical properties of sea sand. Laboratory tests are conducted on samples from 13 bays around Hainan. The results show follows,the silt content of all sand samples satisfy the standard of sand for construction. Most of samples are poorly graded except the grain composition of Yulinzhou is well graded.All the samples from the eastern beach belong to the medium sand and fine sand,while the main ingredient of west beach is coarse sand. Every sample compactness can achieve dense state under smaller preloading（ 50 k Pa）,butmore than half ones just have changes slightly under preloading pressure between 50 k Pa to 100 k Pa. They change a lot when the preloading increase from 100 k Pa to 200 k Pa. The internal friction angles of samples fluctuate about25% from 39. 24°to 48. 24°. The trend of fluctuations is consistent with the mean grain size. The difference of salt content between samples is huge. The maximum one of Jinhai Bay,3. 1g·kg^-1,is almost eight times of that of Lingshui Bay,0. 4g·kg^-1（ the minimum value）.Besides the sand of Qingshui Bay,all sample salt contents of other bays are much higher than the national standard of six over ten thousand. So they must be desalinated if they are used as construction sand.