تغییر شکل گل و لای سفت شده
Abstract
1-Introduction
2-Materials and testing program
3-Results and discussion
4-Conclusions
Declaration of Interest
Acknowledgments
References
Abstract
Solidification using binders is a widespread technique that provides civil engineering applications for silt with poor geotechnical performance. The aim of this study is to investigate the effects of a self-developed lab-made binder (named SEU-2 binder) on the deformation characteristics of silt. For this purpose, a series of one-dimensional consolidation tests, unconfined compressive tests, consolidated undrained triaxial compression tests, Scanning Electron Microscopy (SEM) tests and X-ray diffraction (XRD) tests were conducted on silt specimens and SEU-2 binder solidified silt specimens at 7, 28 and 90 days of curing. Brittleness index was introduced to evaluate the soft-hardening effect of solidified silt quantitatively. It was found that due to SEU-2 binder addition, the deformation characteristics of silt was improved. The initial void ratio and compression index decreased with the increase of SEU-2 binder content. Unconfined compressive strength (UCS) increased with curing time and SEU-2 binder content, while failure strain decreased. Moreover, the shear strength parameters of silt was enhanced due to SEU-2 binder addition, the cohesion increased with the increase of SEU-2 binder content, while the internal friction angle increased and then hardly changed. Additionally, under unconfined compressive tests, the stressstrain curves transformed from dwarf type to lanky type with SEU-2 binder dosage increasing. Under consolidated undrained triaxial compression tests, the stress-strain curves of SEU-2 binder solidified silt behaved as strain softening, while silt exhibited a strain hardening character under high confining pressure, exhibited a strain softening character under low confining pressure. The brittleness index increased with the increase of SEU-2 binder content. SEM analysis revealed that silt structure became denser with an increasing SEU-2 binder content. Furthermore, more network and fibrous hydrates such as C-S-H appeared with the increase of curing time.
Introduction
A silt is a fine-grained soil, or the fine-gained portion of a soil, with a plasticity index less than 4 or if the plot of plasticity index versus liquid limit falls below the ‘A’ line [1]. Silt has the characteristics of sandy soil and clayey soil. Silt with unsatisfactory grading consists of uniform fine-grained soil and its clay content such as montmorillonite and illite is very few. Moreover, silt has low plasticity index, loose, permeable and low cohesion properties and it is easy to hydrate when it is soaked, which determine the weak water cementation and poor anti-scouring performance of silt. The engineering characteristics of roadbed reclaimed with slit which is difficult to compact and easy to hydrate may store up hidden dangers for subgrade deformation, which creates bumps in the roadway and damage to the pavement [2,3]. Therefore, it must be treated to meet engineering requirements. Solidification treatment is one of methods to improve mechanical properties of soil. Solidification not only improves the mechanical properties of soil, but also improves the compactibility characteristics [4].