宁波轨道交通地基土体物理参数概率分布及相关性研究

STUDY ON THE PROBABILITY AND CORRELATIVITY AMONG PHYSICAL PARAMETERS OF FOUNDATION SOIL IN NINGBO RAIL TRANSIT ENGINEERING

利用宁波轨道交通1号和2号线岩土工程勘察成果,研究了典型土层物理参数的概率分布规律,并建立了孔隙比e、塑性指数IP和液性指数IL与天然含水量w和天然密度ρ间的回归经验公式。结果表明:1)宁波地区各典型土层的物理指标均呈良好正态分布规律,ρ、w、e、IP变异性小可视为常量,而IL变异性大在岩土工程可靠性设计中必须作为随机变量处理;2)e、IL均与w呈高度正线性相关;e与ρ呈高度负线性相关;而塑性指数IP-w、IP-ρ以及IL-ρ之间相关性较差。研究结果可为宁波地区勘察设计提供依据。

According to the geologic investigation data of line 1 and line 2 in Ningbo rail transit, the probability distribution of physical parameters for the typical soils in Ningbo area were studied. Empirical equations between the basic physical indexes including the natural density （p） and the natural water content （w） and other physical indexes including the void ratio （e） and the liquid index （IL） and the plasticity index （Ip） were established by means of a regression analysis method. It is found that the physical index probabilities of every typical layer in Ningbo area show a good normal distribution. Furthermore, the physical parameters including p and w and e and Ip have little variation and can be considered as a constant in the practical reliability design. However, the variation of liquid index is large and should be considered as a random variable in the geotechnical reliability design in Ningbo area. Moreover, the physical parameters including a void ratio and a liquid index are in a good positive linear correlativity with the natural water content. Meanwhile, the void ratio is in a good negative linear correlativity with the natural density. However, the plasticity index is in a poor correlativity with the natural density and water content, and the liquid index is also independent on the natural density. Study results could be used as the basis of physical parameters selection in the soil and foundation reliability design in Ningbo area.