不同压实度粉煤灰力学特性试验研究

Experimental Study on Mechanical Properties of Fly Ash with Different Degrees of Compaction

摘要:

粉煤灰作为火电厂排出的工业废渣，不仅需要大量场地堆放，而且严重污染环境。将粉煤灰作为路堤填料用于路基填筑，既可解决火电厂无处堆放和难以处理的问题，又可以满足路基填筑的材料供应，实现固废利用。对粉煤灰的液塑限、最大干密度、最优含水率、自由膨胀率等基本指标进行试验，基于最大干密度和最优含水率，分别测定压实度为90%、92%、95%、97%、100%时的CBR值，回弹模量，压缩模量，快剪强度，三轴压缩强度及耐崩解性能，并对试验结果进行总结分析。试验表明：相比土质细粒填料，粉煤灰液塑限偏高，密度偏小，遇水具有膨胀性；CBR随压实度增大而增大，最大为1.61%，从CBR角度考虑，该粉煤灰不符合路基设计规范中对路基填料CBR的要求；粉煤灰回弹模量随压实度增大而增大，压实度95%时，回弹模量为54.119 MPa，从回弹模量角度考虑，粉煤灰不能作为高速公路与一级公路极重交通下的路床填料，可以用于二级及二级以下公路重交通条件下的路基填筑；内摩擦角和黏聚力均随压实度的增大而增大，快剪试验抗剪强度比三轴压缩试验更高，内摩擦角相近，黏聚力相差较大；粉煤灰的耐崩解时间随压实度增大而增大，在水浸环境下粉煤灰颗粒容易脱散，颗粒间黏结力较弱；纯粉煤灰遇水后没有表现出明显的水化硬化，颗粒间没有明显的黏结现象，没有明显地强度形成。

Abstract:

Fly ash, as an industrial waste residue discharged from thermal power plants, not only requires a large amount of space for storage, but also seriously pollutes the environment. The use of fly ash as embankment filler for roadbed filling can not only solve the problems of nowhere to stack and difficult to treat in thermal power plants, but also meet the material supply of roadbed filling, which realizes the utilization of solid waste. The basic indexes of liquid plastic limit, maximum dry density, optimal moisture content and free swelling ratio of fly ash are tested. Based on the maximum dry density and the optimal moisture content, the CBR value, rebound modulus, compression modulus, fast shear strength, triaxial compression strength and disintegration resistance are measured respectively when the compaction degrees are 90%, 92%, 95%, 97% and 100%, and the test results are summarized and analyzed. The test shows that compared with the soil fine-grained filler, the liquid plastic limit of fly ash is relatively high, its density is relatively low, and it has expansibility when exposed to water. The CBR increases with the increase of compaction degree, and the maximum is 1.61%. From the perspective of CBR, the fly ash does not meet the requirements of the CBR of the roadbed filler in the roadbed design specification. The resilient modulus of fly ash increases with the increase of compaction degree. The resilient modulus is 54.119 MPa when the compaction degree is 95%. From the perspective of resilient modulus, fly ash can not be used as roadbed filler under extremely heavy traffic of expressways and first-class highways, and can be used for the roadbed filling under heavy traffic conditions of highways of second class and below. The internal friction angle and cohesion increase with the increase of compaction degree. The shear strength of the fast shear test is higher than that of the triaxial compression test. The internal friction angle values are similar, and the cohesion values are quite different. The disintegration resistance time of fly ash increases with the increase of compaction degree. In the water immersion environment, fly ash particles are easy to disintegrate, and the bonding force between particles is weak. Pure fly ash will not show obvious hydration hardening after encountering water. There is no obvious bonding phenomenon between particles, and there is no obvious formation of strength.