高炉渣改良填料大型直剪试验分析

将原状高炉渣掺拌粉煤灰分层碾压并重锤夯实作为换填地基的填料,进行分层取样后,以处于干、湿状态下各层土样的混和土作为试样开展大型直剪试验。为了探究高炉渣改良填料的直剪力学特性,以及现有大型直剪仪的不足,对不同法向应力作用下试样的抗剪强度、法向加载板的竖向位移进行了量测,并对试验过程中剪力与剪切位移曲线特性、剪切盒张开状态、完成直剪试验后试样的破碎状态进行了分析。结果表明:因细颗粒不足以填充粗颗粒之间的孔隙,含水量对改良填料力学指标影响很小,改良填料表现为良好的水稳定性;高炉渣改良填料在法向应力小于150kPa时几乎没有黏聚力,而在法向应力大于150kPa时表现出咬合黏聚力;高炉渣混合料直剪试验过程中法向应力越大,初期剪缩量越大,后期剪胀量越小,发生剪胀时对应的剪切位移也越大;在法向应力大于150kPa后,直剪试验的剪胀量有了较大程度的减小,此时剪切面的形成主要以剪切区粗颗粒的剪碎与断裂为主。最后,考虑到现有大型直剪仪随着剪切位移的增加,理论剪切面上的剪切应力与法向应力分布越来越不均匀,且有效剪切面积逐渐减小,为此对大型直剪仪提出了改进建议,使有效剪切面面积保持恒定不变,测试结果与实际情况更加接近,可提高粗颗粒土剪切强度的测试精度。

Features of Large Direct Shear Test for the Improved Filler from Blast-furnace Slag

As filler for replace ground, the raw blast-furnace slag mixed with fly ash, rolling compacted layer by layer, and tamped with heavy hammer. Large direct shear test with the try and wet mixed improved filler of blast-furnace slag, which obtained from filed, is conducted. In order to explore features of the improved filler and the weakness of existing large direct shear apparatus, the shear strength of samples under different normal stress and vertical displacements of the normal stress plate were measured. In addition, the shear stress-shear displacement curve, shear box open state, and samples in crushed and broken states after testing were analyzed. The results show that water content has little influence on the mechanics index. Fine particles could not fill the interspace among coarse particles; hence, the improved filler showed good water stability. There is little occlusion cohesion of the mixed filler when the vertical stress is less than 150 kPa, and occlusal cohesion force is more than 150 kPa. The larger the vertical stress, the greater the shear shrinkage at the initial stage. The less shear dilation in the later stage, the greater the shear displacement as shear dilation occurred. When vertical stress is more than 150 kPa, the shear dilation significantly decreased, and the shear zone is formed by the fragmentation and breakage of coarse particles. Finally, improvements for the large direct shear apparatus were proposed. As the deficiencies of existing large direct shear apparatus, such as shear stress and normal stress are not uniform, the valid shearing area decrease as shear displacement increase. With the improved direct shear apparatus, the valid shearing area is kept constant, and the test results approximate actual conditions, thus improving the accuracy of the shear strength of coarse-grained soil.