表面活性剂随着工业、农业、日常生活等各种活动进入到土体及地下水中，不仅会带来环境污染的风险，还会改变土体的结构等从而影响土体的工程性质。为了合理评估表面活性剂污染土体的工程适宜性，采用阴离子表面活性剂十二烷基苯磺酸钠(SDBS)和阳离子表面活性剂三甲基十六烷基溴化铵(CTAB)对粉土进行改性，通过直剪试验研究其对粉土强度特性的影响。结果表明，表面活性剂改性后的粉土内摩擦角减小，随着表面活性剂浓度的增大，内摩擦角减小的幅值越大，当表面活性剂浓度达2%时，粉土内摩擦角减小23.9%；SDBS改性后的粉土黏聚力大大减小，SDBS浓度为2%时，黏聚力减小91.8%，CTAB改性后粉土黏聚力增大，最大增幅达41.8%；改性粉土中加入不同pH的表面活性剂时，内摩擦角变化很小，表明表面活性剂的酸碱程度对土样内摩擦角影响较小，随着表面活性剂溶液pH的增大，改性粉土的黏聚力呈现出下降的趋势，pH改变了土壤的电荷的分配，改变了土粒间的静电作用，从而引起土体黏聚力的变化。

Surfactants can entry into soil and ground water environment through a number of ways, such as industrial, agricultural and daily activities, and thus lead to environment pollution and the change of soil behaviour. Silty soils are separately modified with anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and cationic surfactant cetrimonium bromide(CTAB), then the strengths of modified silty soils are investigated. The internal friction angle become small when modify by surfactants, and the internal friction angle turn to be more and much smaller as increasing the concentration of surfactants. When the concentration of surfactants reached 2%, the internal friction angle of silty soil decreased approximately by 23.9%. The cohesion decreased by 91.8% when adding 2% SDBS to silty soil, namely, the cohesion of SDBS modified silty soil decrease quite a bit, while that of CTAB modified silty soil increase, and the maximum growth rate is 41.8%. The solution pH have a very slight effect on the internal friction of modified silty soil, while the cohesion of surfactants modified silty soil tend to decline as increasing pH. The change of pH can lead to the change of electric charge on soil surface, resulting in changes of electrostatic interaction between soil particles, and influencing the cohesion of silty soils.