Characters Improved Research On The Backfill Foundation With Baotou Steel Blast Furnace Slag

Blast furnace slag is solid waste exhausted from blast furnace in iron and steel smelting process. As a potential valuable resource, blast furnace slag attract more and more attention of domestic iron and steel enterprises and the relevant scientific institutions. Steel output of our country ranks first in the world, but the comprehensive utilization ratio of blast furnace slag is low. Stacking of blast furnace slag takes up a large amount of farmland, land, not only wastes the resources but also pollutes the environment seriously. Relying on Baotou steel new system project, the performance of the blast furnace slag mixture and application of modified backfill foundation have been researched in this paper to play an guidance role in practical engineering that the blast furnace slag used to fill in the foundation. The main contents and conclusions are as follow:1. The analysis of the physical and chemical properties of Baotou steel blast furnace slag have been made through density text, porosity text, grain analyses text, the heavy compaction test,radioactive assay and stability test, research shows that natural unit weight of Baotou steel blast furnace slag is14.36kN/m3, it’s radioactivity satisfy requirements of the design code.The cubage stability of Baotou steel blast furnace slag is good, it is noncorrosive and nontoxic. Blast furnace slag contains many pores, the content of coarse particles is larger, it can be used for engineering backfill by blending a percentage of fine fractions.2. This paper designs five groups of mixture which is composed of different content of blast furnace slag, fly ash and Baotou local sand. Through large direct shear test for five groups of mixture, results show that the main control factor of the shear strength is the content of coarse material. Shear strength get maximum value in the range of P5=60～75%. Adding sand not only increase the fines, improved the gradation, but also increases the shear strength. When P5=65-70%, the compacting effect is the best, filler has high shear strength.3. Compressed indexes of mixture under multi-stage loading、offloading by steps multi-stage loading again can be get through large compression test for five groups of mixture. Compared with the original scheme, the compression modulus values of modified mixture obviously increased, the effect of modifing is significant. Range of P5=62～68%mixed with sand can be made as the filler control range. The matching raw material mix ratio is:original slag66～73%, fly ash3～4%, sand30～23%, moisture content around4%.4. According to the characteristics of blast furnace slag and modified mixture, combined with engineering background, this paper put forward the separation rolling dynamic compaction construction scheme. And briefly explain both of the construction technology. Some advice given for the attention of the construction scheme.