A study on the effects of lime on the mechanical properties and behaviour of London clay

Lime is commonly used as a stabiliser to improve the engineering properties of soils in particular for roads and pavement foundation. Despite the popularity of the technique, only a limited amount of existing experimental data for lime treated soils from advanced testing is available, in part due to the length of the tests. As lime stabilisation is increasingly used for other engineering applications (e.g. embankments, railway layers, canal linings, earth dams, buildings...etc), advanced testing to describe the mechanical behaviour of the treated soils is required. In this research a comprehensive experimental program was carried out to investigate the engineering properties and behaviour of a lime treated high plasticity clay (London Clay). A number of Unconsolidated Undrained (UU), Consolidated Drained (CD) and Consolidated Undrained (CU) triaxial tests were performed to identify the effect of lime dosage, compaction water content and curing time on the shear strength parameters, stressstrain behaviour, volumetric response and dilation of the treated soil. Moreover the study focused on understanding the mineralogical and physicochemical transformations occurring during the curing stage. Based on a number of additional tests (XRD analysis, pH measurement and other chemical testing) they provided a useful reference for the interpretation of the triaxial test results; in order to support hypotheses made on the evolution of the chemical reactions and the development of cementation bonds. Results from CD tests showed that yield, peak, and ultimate strength were greatly improved by an increase in lime content. London Clay samples treated with lime showed a considerable increase in peak stress ratio ( ) peak q / , particularly at lime addition beyond p' the initial consumption of lime (ICL). An increase in the angle of shearing resistance and cohesion intercept with increasing lime content was observed consistently. The stress– strain behaviour of treated London Clay was observed to be nonlinear with a contractive– dilative response. This response is found to be strongly influenced by lime content and the curing period. An increase in dilation with lime amount as well as a progressive suppression in the dilation by the effective stress increase was also observed. A Critical State Soil Mechanics (CSSM) framework was used to interpret the results. Lime addition, curing time and compaction water content were observed to have an impact on the critical iv state parameters in the compression plane (v − p'). However, the overall critical state line (CSL) in the stress space (q − p') of lime treated London Clay appears to be almost parallel to untreated London Clay CSL at the same M value, but lying above the untreated CSL with a cohesion intercept. Moreover, the domain where the untreated soil subsists was observed to expand with lime addition and further enlarge with an increase in the lime content. These features can be further explored by deriving a suitable constitutive model for predicting the mechanical behaviour of lime treated soils.