【摘要】 膨胀土是一种具有多裂隙性、超固结性和反复胀缩性的非饱和土。在干湿气候交替变化的环境中会因其湿胀干缩的变形导致工程事故的发生,通过化学改良法改善水土间相互作用,可达到改良膨胀土工程特性的目的。利用钢渣粉作为新型固化剂,与水泥组合改良膨胀土,研究改良膨胀土在干湿循环条件下力学特性变化规律及其改良机理。将纯膨胀土(Es)、水泥改良膨胀土(Es-C)、钢渣粉-水泥改良膨胀土(Es-SSP-C)和钢渣粉-水泥-NaOH改良膨胀土(Es-SSP-C-N)4种土体进行不同次数干湿循环作用后,进行体积变化率试验、不固结不排水三轴压缩试验、无侧限抗压强度试验。试验结果表明,改良土体的体积变化率较未改良土试样有了相当大的减小;改良膨胀土强度有大幅度提升,并且其强度关系总有Es-SSP-C-N>Es-C>Es-SSP-C>Es;在干湿循环作用下改良土仍能保持较高的强度水平,且随循环次数增加强度有所提升。利用扫描电镜(SEM)和能谱分析(EDS)技术对4种土体在干湿循环次数变化时的微观形貌和物相成分进行分析,发现水泥和钢渣粉水化致使土体颗粒变得密实,水化硅酸钙(C-S-H)和水化铝酸钙(C-A-H)等水化产物逐渐增多,弱化了干湿循环中水的侵蚀作用,确保其强度在干湿循环过程中保持稳定。更多还原

【Abstract】 Expansive soil is unsaturated soil with multiple fractures,super-consolidation,and repeated expansion and contraction.In the environment where the dry and wet climate changes alternately,engineering accidents may occur due to the deformation of the swelling and shrinking of expansive soils.The chemical method of improvement is often used to enhance the interaction between soil and water so as to improve the engineering characteristics of expansive soils.In this paper,steel slag powder was used as a new curing agent combined with cement to modify the expansive soil,whose mechanical property variation law and mechanism under dry-wet cycles were studied.The dyewet cycles tests were performed on the expansive soil(Es),which is improved by cement(Es-C),improved by cement and steel slag powder(Es-SSP-C),modified by cement and steel slag powder and NaOH(Es-SSP-C-N)respectively.Afterwards,the volume change rate test,the unconsolidated undrained triaxial compression test(UU test),and the unconfined compressive strength test were conducted on these samples to study the mechanical properties such as the shear strength and related indexes.The results show that the volumetric change rate of the modified soil is considerably reduced compared to the unmodified soil sample,that the strength of the modified expansive soil is greatly improved,and its intensity relationship is Es-SSP-CN>Es-C>Es-SSP-C>Es.Moreover,the improved soil under the dry-wet cycles can still maintain a high level of strength,and that the strength increases with the number of cycles.Scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)were then used to analyze the micro-morphology and phase change of four types of soils during the change of the number of dry-wet cycles.It is found that the hydration of cement and steel slag powder leads to compactness of soil particles,and hydration products such as calcium silicate hydrated(C-S-H)and calcium aluminate hydrate(C-A-H)gradually increase,which weakens the erosion effect of water in the dry-wet cycle and ensures its strong stability during the dry-wet cycles.更多还原