基于染色标定的钙质砂颗粒破碎级配转移矩阵试验研究

Experimental study on the gradation transition matrix of dyed carbonate sands during particle breakage

颗粒破碎导致的级配演化对土体的物理力学性质有显著影响,掌握土体的颗粒破碎演化规律具有重要的现实意义。级配转移矩阵是一种可有效反映详细颗粒破碎过程的级配演化方法。为建立更接近多粒径组真实破碎情况的级配转移矩阵模型,对钙质砂开展了不同初始级配与相对密实度D_(r)的侧限压缩试验。将不同粒径组的钙质砂分别染成不同颜色,基于PCAS图像识别技术,探讨了在不同影响因素下颗粒破碎过程中多粒径组中各单粒径组的破碎情况。试验结果表明,较大粒径组的存在会促进较小粒径组的破碎,而较小粒径组的存在会抑制较大粒径组的破碎;多粒径组试样中各单粒径组的级配演化符合分形分布规律,且多粒径组中的各单粒径组的相对破碎率B_(ri)*与单位体积输入功W_(in)呈线性关系。在此基础上,建立了多粒径组试样的级配转移矩阵的求解模型,试验结果表明,该方法能较好地预测不同级配试样的颗粒破碎演化规律,且该方法可以考虑试样中各单粒径组之间的相互影响,能得到较为详细、真实的颗粒破碎规律,为研究颗粒破碎问题提供了新思路。

Breakage-induced evolution of particle size distribution(PSD)has a significant impact on the physical and mechanical properties of soil.It is therefore of great practical significance to study the evolution of particle breakage.The gradation transition matrix provides an effective approach to describing the detailed particle breakage of granular soils.This paper presents a series of one-dimensional compression tests on carbonate sands with different initial conditions(i.e.,PSD,relative density)to establish the gradation transition matrix of sample with more detailed information on particle breakage of each size group.The breakage of each single-sized particles of soil samples with multi-sized particles under different initial conditions is explored based on the dyeing and PCAS image recognition technologies.The results show that the presence of small-sized particles plays a negative effect on the breakage of the large-sized particles,while the presence of large-sized particles promotes the breakage of the small-sized particles.The PSD of each single-sized particles of a carbonate sand sample evolves towards the fractal distribution,and the relative breakage index B_(ri)* of each single size group is linear with the input work per unit volume W_(in).Finally,the breakage transition matrices of both uniformly and non-uniformly graded carbonate sands are established with consideration of interactions between particles with different sizes,which demonstrates its satisfactory performance.The proposed method provides a new insight into the evolution of particle breakage of granular soils with more detailed information of each size group.