冻融循环作用下木质素磺酸钙改良黄土的力学特性研究

木质素磺酸钙作为一种绿色环保的改良材料，近年来被应用于土体加固领域。为探究木质素磺酸钙对黄土的固化效果，通过开展侧限浸水压缩试验、冻融循环试验、不固结不排水三轴剪切试验、扫描电镜试验和X射线衍射试验，分析冻融循环次数、掺量和围压对木质素磺酸钙改良黄土力学性质和微观机理的影响规律。研究结果表明：掺入木质素磺酸钙，可有效消除黄土的湿陷性。此外，改良黄土的应力-应变曲线随木质素磺酸钙掺量的增加向一般硬化型转变，而随着冻融循环次数的增加，应力-应变曲线向弱硬化型转变。改良黄土的破坏强度随木质素磺酸钙掺量的增加呈先增大后减小的趋势，木质素磺酸钙掺量为1%时破坏强度最高，各掺量改良黄土随冻融循环次数的增加先减小后趋于稳定，同时抗剪强度指标呈现下降的趋势。通过扫描电镜试验和X射线衍射试验，发现改良黄土内部有胶结物生成并填充了土颗粒间的孔隙，使土体密实度提高，进而提高土体强度；而冻融作用导致土颗粒的接触方式由面-面接触向点-点、点-面接触过渡。此外，木质素磺酸钙改良黄土中未发现有新的矿物成分生成，且冻融作用未造成土体矿物成分的消解。

Experimental study on mechanical properties of calcium lignosulfonate modified loess under freeze-thaw cycle

Calcium lignosulfonate， as an environmentally-friendly improved material， has been applied to the field of soil reinforcement in recent years. In order to explore the solidification effect of calcium lignosulfonate on loess， indoor tests such as confined immersion compression test， freeze-thaw cycle test， unconsolidated undrained triaxial shear test， scanning electron microscope test and X-ray diffraction test were carried out to analyze the effects of freeze-thaw cycle times， content and confining pressure on the mechanical properties and microscopic mechanism of calcium lignosulfonate improved loess. The results show that： adding calcium lignosulfonate can effectively eliminate the collapsibility of loess. In addition， with the increase of calcium lignosulfonate content， the stress-strain curve of improved loess changes to general hardening type， while with the increase of freeze-thaw cycles， the stress-strain curve changes to weak hardening type. The failure strength of improved loess increases first and then decreases with the increase of calcium lignosulfonate content， and the failure strength is the highest when the calcium lignosulfonate content is 1%. With the increase of freeze-thaw cycles， the failure strength of improved loess decreases first and then tends to be stable， while the shear strength index shows a downward trend. Through scanning electron microscope test and X-ray diffraction test， it is found that cement is formed in the improved loess and fills the pores among soil particles， which improves the compactness of the soil and the strength of the soil. However， the freezing and thawing effect causes the contact mode of soil particles to change from surface-to-surface contact to point-to-point contact and point-to-surface contact. In addition， no new mineral components were found in the loess improved by calcium lignosulfonate， and the freezing and thawing did not cause the dissolution of mineral components in the soil.