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海南岛西北部洋浦湾北侧滨海地区地层中揭露出一层更新世半成岩胶结砂层,由于目前我国《岩土工程勘察规范》中尚无对半成岩胶结砂层有明确的定义和勘察技术要求,如何分类评价和利用这一特殊岩土体成为工程设计中的主要问题。工程勘察分析表明,从其组成、结构和构造等方面来看,该土层尚处在一种由砂土层向成岩方向发展的半成岩过程中,既有显著的砂土特征,又有部分成岩的特征;从分类评价上来看,它是一种在特定沉降环境条件下形成的、类似于硬土-软岩的特殊岩土体。实际工程中,将该土层勘察中的取芯率作为辅助指标,用以评价该类土层的均衡性,并通过取芯率对土的压缩性指标进行修正,以期获得基础沉降计算的合理值。
A layer of Pleistocene semi-diagenetic cemented sand is revealed in the strata on the north side of Yangpu Bay in the northwest of Hainan Island. Since there is no clear definition and investigation of semi-diagenetic cemented sand in the “Geotechnical Investigation Regulation” Technical requirements, how to classify the evaluation and use of this special rock and soil engineering has become the main problem. Engineering survey shows that from the aspects of its composition, structure and structure, the soil layer is still in the process of semi-diagenesis from sands to diagenesis. It has both obvious sand characteristics and some Diagenetic characteristics; from the point of view of classification, it is a special rock and soil formation similar to hard-soft rock formed under specific sedimentary environmental conditions. In practical engineering, taking the coring rate in the soil survey as an auxiliary index to evaluate the balance of this kind of soil and revising the compressibility index of soil through the coring rate, in order to get the reasonable calculation of foundation settlement value.