The acceleration of the peat secondary consolidation due to the sorption of bound water with disperse clay

Abstract

According to observations at the experimental site, the primary consolidation of the 6-6.5 m peat layer completed in 3-5 years after the sandy embankment was filled on. Secondary consolidation of peat caused by the removal of bound water from micropores and channels within vegetation remains is the cause of settlement that has not stabilized for decades. The aim of laboratory research was to evaluate the effects of two methods for peat settlement stabilization at the stage of secondary consolidation – vacuuming and sorption of bound water of disperse clay. Tests were carried out with peat, which has a degree of decomposition of 40-45 %, a density of 0.98–1.12 g/cm3, a void ratio of 11.8–13.8. Samples with a diameter of 87 mm and a height of 30, 50 and 70 mm were set into odometers and maintained under a load of 25, 50 and 100 kPa for 5-6 months, after that experiments to stabilize secondary consolidation were started. In contrast to vacuuming, the use of pre-dried clay with the following properties turned out to be very effective: maximum hygroscopic water content 43%, liquid limit 198%, plastic limit 58%, specific surface area 411 m2/g. The volume of clay was about 20% of the volume of peat samples. Deformations of samples due to water sorption by clay increased within 2-4 days and reached 0.09-0.11 of their initial height. The penetration of clay into the peat can be performed by drilling of boreholes, vibration stamping and other methods.