南沙港区深厚淤泥软土特性及空间异性研究

Study on Characteristics and Spatial Heterogeneity of Deep Silt Soft Soil in Nansha Port Area

软土参数作为岩土工程勘察的关键指标,是研究软土特性及解决工程问题的前提和依据。以广州南沙港区深厚淤泥及淤泥质软土为研究对象,共收集371组室内试验及147组原位测试资料,采用数理统计方法及随机场理论对软土参数空间特性进行研究。结果表明:软土表现为“四高一低”,即含水量高、液限高、孔隙比大、压缩性高、抗剪强度低,具有较强的区域性及空间异性,时空效应显著。建立了软土参数之间的经验公式,发现软土物理指标相比力学指标稳定性较好,变异系数较小,具有更强的相关性;随着软土深度的增加,含水量、孔隙比、压缩系数、液限及液塑性指数呈减少趋势,天然密度、压缩模量、强度指标及静力触探指标呈缓慢增长趋势,十字板抗剪强度呈先减少后增大趋势;自相关距离随探孔深度的增加无明显相关性,采用锥尖阻力指标能更好地反映土层的空间变异特性及试验结果的重现性,实现软土参数由“点”特征向“空间”特性的转变;提出了该区域软土判定标准建议值,为类似地区淤泥软土勘察设计、软基处理及施工提供参考。

As the key index of geotechnical engineering investigation,soft soil parameters are the premise and basis for studying soft soil characteristics and solving soft soil engineering problems.Taking the deep soft soil in Nansha port area of Guangzhou as the research object,371 groups of indoor geotechnical tests and 147 groups of field in-situ test data were collected,and the spatial characteristics of soft soil parameters are studied by mathematical statistics and random field theory.The results show that:Soft soil shows"four high and one low",to be specific,high water content,high liquid limit,large void ratio,high compressibility and low shear strength,it has strong regional and spatial heterogeneity,and the space-time effect is significant;The empirical formula between soft soil parameters are established,it is showed that the physical indexes of soft soil have better stability,smaller coefficient of variation and stronger correlation than the mechanical indexes;The water content,void ratio,compression coefficient,liquid limit and liquid-plastic limit index decrease with the increase of soft soil depth,while natural density,compression modulus,strength index and static cone penetration index increase slowly,the shear strength of vane first decreases and then increases;The autocorrelation distance has no obvious correlation with the increase of exploratory hole depth,the cone tip resistance index can better reflect the spatial variation characteristics of soil layer and the reproducibility of test results,and realize the transformation of soft soil parameters from"point"characteristics to"spatial"characteristics;The recommended value of soft soil judgment standard in this area is put forward,which provides a reference for the survey and design,soft foundation treatment and construction of silt soft soil in similar areas.