一种测定超大砾石混合土干密度的新方法

摘要

This paper presents a novel computational procedure for the maximum dry density of mixed soils containing oversize particles. At first, the large-scale compaction test data for mixed soils are analyzed by an artificial neural network to determine the main factors affecting the compaction. These factors are then imposed on a genetic programming method and a new mathematical equation emerges. The new equation has more conformity with the experimental data in comparison with the previous correction methods. Besides, the mixed soil dry density is associated with most base soil and oversize fraction specifications. With regard to the sensitivity analyses, if the mixed soil contains high percentages of oversize fraction, the mixed soil composition is governed by the specification of oversized grains, such as specific gravity and the maximum grain size and by increasing these factors, the mixed soil dry density is increased. In mixed soil with a low content of oversize, the base soil specification mainly controls the compaction behavior of mixed soil. Furthermore, if the base soil is inherently compacted with greater dry density, adding the oversize slightly improves the mixed soil dry density. In contrast, adding oversized grains to the base soil with a lower dry density produces a mixed soil with greater dry density. By increasing the maximum grain size difference between the oversize fraction and base soil, the dry density of mixed soil is enhanced.%提出一种计算超大颗粒混合土最大干密度的新方法.首先,利用人工神经网络对混合土的大规模压实试验数据进行分析,确定影响压实度的主要因素.然后,将这些因素加到遗传规划方法中,得到一个新的数学方程.与以往的修正方法相比,新方程与实验数据更符合.此外,混合土干密度与大多数基层土和超大颗粒的比例有关.在敏感性分析方面,当混合土中含有较大比例的超细粉土时,混合土的组成受超大颗粒的规格(如比重和最大粒径)的控制,而随着这些因素的增加,混合土壤的干密度也随之增大.在超大颗粒含量较低的混合土中,基层土主要控制混合土的压实特性.此外,如果基土以较高的干密度压实,加入过大的颗粒会稍微改善混合土的干密度.相反,在干密度较低的基层土壤中添加过大的颗粒会产生干密度较大的混合土.通过增大超细粉土与基土的最大粒径差,提高了混合土的干密度.