膨胀土具有强胀缩性，吸水极易膨胀软化，失水急剧收缩硬裂，这种胀缩性给工程结构造成很大危害。采用稻壳灰（ricehusk ash，RHA）和高炉矿渣（ground granulatedblast-furnace slag，GGBS）作为固化剂对膨胀土进行稳定化，通过击实试验、无侧限抗压强度试验、直剪试验、加州承载比（Californiabearing ratio，CBR）试验、膨胀试验、扫描电镜试验和X射线衍射（X-ray diffraction，XRD）试验，研究了固化后膨胀土的力学强度、膨胀特性变化规律及微观机制。试验结果表明：在不同配比和掺量的固化土中，稻壳灰−矿渣为6:4配比和10%掺量固化土无侧限抗压强度最大；稻壳灰−矿渣（RHA-GGBS，RG）可降低膨胀土轴向变形，提高抗剪强度，随着固化剂掺量增加，固化土黏聚力先增大后减小，内摩擦角逐渐增大；与未处理的膨胀土相比，掺稻壳灰−矿渣固化土CBR值最高可提高至7.9倍，路基土的力学强度得到了显著改善。稻壳灰−矿渣可明显改善膨胀土的膨胀率，减小膨胀力，无荷膨胀率最多可从11.4%下降到0.5%，有荷膨胀率最多可从1.1%趋于0%，膨胀力降幅介于12.1%～62.8%之间。稻壳灰−矿渣可以促进团聚体、无定型水化产物和极少量钙矾石（AFt）的形成，分布在土体表面并填充孔隙，同时可明显减少土中蒙脱石和伊利石亲水矿物成分，增强颗粒之间的胶结作用，从而提高路基土的力学强度，降低固化土膨胀性能。Expansive soil has strong swelling-shrinkage behavior. It swells and softens afterabsorbing water

and shrinks and cracks after losing water. These swelling-shrinkagebehavior will seriously threaten engineering structures. In thisstudy

the expansive soilwas stabilized by rice husk ash (RHA) and ground granulated blast-furnace slag(GGBS). Throughcompaction test

unconfined compressive strength test

direct shear test

California bearing ratio (CBR) test

swelling test

scanning electronmicroscope test and X-ray diffraction (XRD) test

the mechanical strength

expansion characteristics and microscopic mechanism of solidified expansivesoil were studied. Testingresults show that the unconfined compressive strength of the stabilized soilwith a ratio of RHA to GGBS of 6:4 and a 10% curing agent dosage is the highestamong all stabilized soils. Themixture of rice husk ash-ground granulated blast furnace slag (RG) can reduce axialdeformation and improve shear strength. With the increase of curing agent content

the cohesion of stabilized soil increases first and then decreases

and theinternal friction angle increases gradually. Compared with the untreated expansive soil

the CBR value of the stabilized soil with RG can beincreased to 7.9 times

and the mechanical strength ofthe soil has been significantly improved. RG can significantly reduce the swellingrate of expansive soil and the swelling force. The free swelling rate can bereduced from 11.4% to 0.5%

and the swelling rate with loading can be reducedfrom 1.1% to 0%. Additionally

the swelling force decreases between 12.1% and62.8%. RG can promote theformation of flocculation

amorphous hydration products and a very small amountof ettringite (AFt)

which are distributed on the surface of the soil and fillthe pores so as to improve the strength of the soil and reduce the expansion ofthe soil. Meanwhile

RG can significantly diminish the hydrophilic minerals suchas montmorillonite and illite in the soil and thus enhance the cementationbetween particles

thereby improving the strength and downgrading theswelling behavior of the expansivesoil.