Mechanical behaviour of low–medium density destructured White Chalk

Abstract

Low- and medium-density White Chalk often destructures during civil engineering works, forming a putty that exhibits problematic low strengths in the short term but may build-up strength with time. The underlying mechanisms that control the mechanical performance of the material are not well understood. This paper explores the prospect of developing a framework to characterise the behaviour of chalk putty. To this end, triaxial tests were carried out using low- and medium-density reconstituted chalks produced by different methods. Using void ratio against mean effective stress results, a unique critical state line (CSL) is proposed, regardless of parent rock origin or the crushing process used to generate the putty material. The CSL was also found to satisfactorily fit independent test data by various authors, even though each independent sample material may have had different ‘intrinsic’ CSLs. This was suggested to stem from the similar particle characteristics of the chalks used. An assessment of the ageing effect indicates increases in strength as a result of densification due to consolidation and secondary compression, however, the end-of-test state could still be described using the CSL.