崩解性砂软岩改良弱膨胀土性状实验研究

EXPERIMENTAL STUDY ON PROPERTIES OF WEAK EXPANSIVE SOIL IMPROVED BY DISINTEGRATED SANDSTONE

引江济淮河(航)道工程引江济巢段和江淮沟通段地层连续分布弱膨胀土和具有崩解性的砂软岩,为资源化利用河道开挖弃渣开发非膨胀土来源,实验研究利用崩解性软岩改良弱膨胀土的可行性。研究表明:崩解性砂软岩易粉碎、无膨胀性、天然含水率低,具备作为改性材料的条件;弱膨胀土掺入崩解性砂岩后其膨胀率、膨胀力、最优含水率与掺入量负相关,最大干密度、渗透系数与掺入量正相关;弱膨胀土掺入崩解性砂岩后其内摩擦角随掺量呈反S型曲线规律发展,黏聚力随掺量增加近似呈二次曲线规律衰减,掺量高于30%时,改良土的抗剪强度可能低于天然弱膨胀土;在砂岩掺量及粒径范围相同情况下,砂岩粗颗粒含量越高,改良土的黏聚力越高和摩擦角越低;砂岩改良土在干湿循环条件下的强度稳定性得到改善,且水化砂岩的改良效果优于机碎砂岩。以弱膨胀土改良后强度不损失为标准,确定砂岩合理掺量为30%,并须合理控制砂岩改良土施工过程中机碎砂岩中粗粒组的含量。

Continuous distribution of weak expansive soil and collapsible sand soft sandstone exists in Jichao and Jianghuai connecting sections of the Yangtze River to Huaihe River(waterway)diversion project.In order to utilize river excavation waste to develop non-expansive soil,the feasibility of using collapsible soft sandstone to improve weak expansive soil is studied.The results show that the disintegrated sandstone is easy to become fines and has low natural water content without expansion.So it can be used as a modified material.The expansion rate,expansion force,optimum water content and the amount of incorporation are negatively related when the weak expansive soil is mixed with the disintegrated sandstone.The maximum dry density,permeability coefficient and the amount of incorporation are positively related.After the weak expansive soil is incorporated into the disintegrated sandstone,its internal friction angle develops with the inverse S-shaped curve law,and the cohesive force decreases approximately quadratic with the increase of the dosage.The shear strength of improved soil may be lower than that of natural weak expansive soil when the dosage is higher than 30%.The higher the content of coarse grains of disintegrated sandstone,the higher the cohesion and the lower the friction angle of the improved soil when the content and the size range of disintegrated sandstone are the same.The strength stability of sandstone improved soil under dry and wet cycling conditions is improved.The improvement effect of the hydrated disintegrated sandstone is better than that of the crushed disintegrated sandstone.According to the standard of no loss of strength after the improvement of weak expansive soil,the reasonable content of disintegrated sandstone is determined to be 30%.And the content of coarse-grained group in the machine crushed disintegrated sandstone has to be reasonably controlled during the construction of disintegrated sandstone improved soil.