光华同济大学土木工程学院基金——光华讲座教授讲座
Kwang-Hua Chair Professor Lecture

主讲人：Professor Cui Yu-Jun, Ph.D. Ecole des Ponts ParisTech, France 时间: 9:00 a.m. Monday, August 16, 2010 地点: Room 201, Department of Geotechnical Engineering, Tongji University (岩土楼201) 联系人：叶为民 教授

题目1：Laboratory Hydro-mechanical Characterisation of Boom Clay at Essen and Mol
Abstract:
Boom clay has been selected as a potential host rock formation for the geological disposal of radioactive waste in Belgium. In the present work, the hydro-mechanical behaviour of Boom clay taken from Essen site at a depth of 220 - 260 m and from Mol site at 223-m depth was investigated in laboratory by performing low pressure odometer tests (vertical effective stress ranging from 0.05 to 3.2 MPa), high pressure odometer tests (vertical effective stress ranging from 0.125 to 32 MPa), isotropic consolidation tests (confining effective stress ranging from the in-situ stress to 20 MPa) and triaxial shear tests. It has been observed that the mineralogy, geotechnical properties and hydro-mechanical behaviour of Boom clay from Essen at 227-m, 240-m and 248-m depths are similar to that of Boom clay from Mol. As in the case of Boom clay at Mol, the failure line of Boom clay at Essen in the p’-q plane is also not linear. The slope of the portion beyond the pre-consolidation stress for Boom clay from Essen is almost the same as for Boom clay from Mol, suggesting a similar internal friction angle of about 13°. From a practical point view, the laboratory test results on Boom clay from Essen and their comparison with those of Boom clay from Mol provide important information regarding the transferability of knowledge on Boom clay at different sites, taking into account the fact that most investigations have been carried out at Mol site.

题目2： Investigating the pore-water chemistry effects on the volume change behaviour of Boom clay
Abstract:
The Essen site has been chosen as an alternative site for nuclear waste disposal in Belgium. The soil formation involved at this site is the same as at Mol site: Boom clay. However, owing to its geographical situation closer to the sea, Boom clay at Essen presents a pore water salinity 4-5 times higher than Boom clay at Mol. This study aims at studying the effects of pore water salinity on the hydro-mechanical behaviour of Boom clay. Specific odometer cells were used allowing "flushing" the pore water in soil specimen by synthetic pore water or distilled water. Mechanical loading was then carried out on the soil specimen after flushing. The results show that water salinity effect on the liquid limit is negligible. The saturation or pore water replacement under the in situ stress of 2.4 MPa does not induce significant volume change. For Ess83, hydro-mechanical behaviour was found to be slightly influenced by the water salinity; on the contrary, no obvious effect was identified on the hydro-mechanical behaviour of Ess96. This can be attributed to the higher smectite content in Ess83 than in Ess96.

题目3：Investigating the Swelling Pressure of Compacted Crushed-Callovo-Oxfordian Argillite
Abstract:
An experimental study was conducted on the swelling pressure of heavily compacted crushed Callovo-Oxfordian (Cox) argillite at a dry unit mass ?d = 2.0 Mg/m3 using four different methods: constant-volume, swell-reload, zero-swell and adjusted constant-volume method. Results show that the swelling pressure varies in the range 1-5 MPa and significantly depends on the test method; From the constant-volume tests, it is observed that the swelling behaviour during wetting is a function of the suction applied and depends on the hydration paths followed and of wetting conditions (e.g. vapour-wetting or liquid-wetting). The swelling pressure decreases significantly with saturation time. To identify the microstructure changes of specimens before and after wetting, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) tests were performed. It is observed that, after wetting, the large inter-aggregate pores observed in the as-compacted specimen are no longer apparent; the whole pattern is characterized by a general swelling of hydrated clay particles, rendering the soil more homogeneous. Results from MIP evidenced that wetting caused a significant reduction of the entrance diameter of the dominant inter-aggregate pores mode from 2.1 to 0.5 ?m whereas intra-aggregate pores do not seem to be significantly influenced.