| Prepacked Aggregate Concrete(PAC) in China is being used as a reinforcement application process,which has unique advantages in many engineering fields. Prepacked Aggregate Concrete Technology Core - filling process directly determines its quality, but currently few studies on the core technology are made.therefore, it is necesarry to adopt a reasonable theoretical model of factors influencing the grouting process and mechanism analysis to identify the internal laws of groutign process of prepacked aggregate concrete, which can provide scientific guidance for the site construction.The main technical parameters of PAC are:the rheological properties of mortar, the porosity of preplaced aggregate,grouting pressure,and the spacing of the grouting holes.The target of the study on the grouting process is to abstract reasonable theory models and analysis the theoritical relationship during these parameters.The grouting mortar of PAC is described as a Binghanm fluid this paper.The entirety of preplaced aggregate in the formwork is also discribed as a rigid porous media.The pore of the aggregate is discribed as a bunch of capillaries which has a certain distribution of tortuosity and diameter.So the theoretical model of grouting process can be made—Under the action of the grouting pressure,grouting mortar with Binghanm rheological properties,flows through a bunch of caplliaries with certain distribution in the preplaced aggregate porous media, which also shows a specific flow characteristics.The goal of this paper is to indentify the relationship and inner action mechanics of the influencing factors.In order to describe the complexity and randomness of distribution for the porous media's inner pore and the particle's size ,the concept of tortuosity and fractal theory are introduced. Microstructure of porous media, such as the pore size's distribution or the particle's distribution, comply with the fratal theroy in a certain range of size or in statistics. This paper uses the geometric analysis method to study the turorisity of the streamlines in the cases of three-dimensional spherial particles in porous media, makes weighted-average to calsscic streamlines'turtosity and derives the expression of the turtosity when the fluid flows through the porous meida.This paper develops the expression for flow rate, velocity and starting pressure gradient for grouting mortar-Binghanm fluid in prepalced aggregate porous media through theorical study. We also make a detailed analysis of influence factors for starting pressure gradient, which is a function of porousity, the rheological parameters and so on. The present models relate the grouting mortar-Binghanm fluid to the sturcture parameter of preplaced aggregate porous media, then the physical mechanism for the grouting mortar flow in pores of Prepacked aggregate media during the grouting process is well understood. We also study the grouting mortar-Binghanm fluid's plane parellel flow in prepalced aggregate porous media. Based on the fractal distribution of the imagnary caplliaries'turtosity and diameter, the fractal expression for porosity, flow rate, velocity for parallel flows and the pressure distribution equation are developed. Finally we abtain the values for the rheological parameters of grouting mortar and the porosity of prepalced aggregate porous media, according to the dates from experiments and references. Futherly we get the referenced values of starting pressure gradient, mean velocity flow rate of cross—section.and Filling-height for the Binghanm fluid thourht this rigid porous media. |
