Investigation into strength development mechanism of lime-modified dehydrated clay of slurry shield tunneling operation

Large amount of waste soil is produced during shield tunnel construction. to the goal of achieving the resource utilization of it becomes more urgent. In this study, dehydrated clay was first obtained by centrifuged method from a slurry shield tunneling project. A series of laboratory tests, such as the Atterberg limits, Unconfined Compressive Strength (UCS), water transformation in different forms and microscopic tests, were then conducted to investigate physical properties and micro-mechanisms of lime treated clay. The results demonstrated that the I-P, q(u), and water stability of the dehydrated clay increases significantly with the increase of a(c) and T. However, requirements of q(u) (>= 500 kPa) and I-P (< 26) for ordinary highway subgrade fill can be met (T=7d) only at a(c) >= 15 %. The filling effect of the crystalline hydration product Ca(OH)2 and the bonding effect of hydrated calcium silicate (C-S-H)in the modified clay are the fundamental reasons for the improvement of soil strength and stability. The strength of the modified clay was increased with bound water content exponentially, while the strength of the modified clay was increased with mineral water content linearly. The outcome of the study provides benchmark for the reuse of dehydrated clay generated from slurry shield tunneling construction process.