Relationship between crack formation and soil water suction due to desiccation of mineral liners for landfills

Mineral liners are subjected to a temperature gradient during the operating phase of a waste disposal site. A moisture transfer takes place and desiccation and crack formation will be caused. Mineral liners can lose their impermeability and sealing effect, in which case, leachate may pollute the ground water. The paper focuses on the relationship between the formation of desiccation cracks in clayey soils and soilwater suction, in relation to temperature, water content and void ratio parameters. Its main topics are the analysis of moisture transfer due to both temperature and moisture gradients and the tensile strength of clayey mineral liners. The soil water characteristics of a kaolinite have been determined experimentally using tensiometers and the vacuum desiccator method. Soil-water suction for values of pF between 0 - ca. 3 and 5 - 7 have been measured. Water transfer coefficients such as the isothermal and thermal diffusivity and the unsaturated hydraulic conductivity have been determined. The laboratory model used is presented. The relationships between water transfer coefficients and water content are shown in a series of figures. A tension apparatus is presented for determining the tensile strength of clayey soils as a function of water content, temperature and radial pressure. Test results are given. Furthermore, a short overview of a numerical model is shown to describe crack formation in relation to moisture flow.

• 1 INTRODUCTION

• 2 THE pF-CURVE

• 3 MOISTURE TRANSFER

• 4 TENSILE TESTS

• 5 NUMERICAL MODEL TO PREDICT CRACK FORMATION

• 6 CONCLUSION

• ACKNOWLEDGEMENT

• REFERENCES