The Static Behavior of Calcite Cemented Gravely Sand – Tehran Alluvium Case Study

Adl, Mahmoud Reza | 2008

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39034 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. An understanding of the effect of degree of cementation on static behavior of cemented soils in becoming increasingly important in design and analysis of geotechnical engineering problems. Naturally cemented coarse-grained soils are widely present in many parts of the world. Misunderstanding of the behavior of such soils could lead to under or overestimate of the soil parameters. Previous studies conducted by Prof. Haeri and his co-workers show that most of the alluvial deposit of Tehran, the capital city of Iran. The amount and characteristics of the cementation of the deposit varies in different parts from highly cemented in the north to non-cemented in the south. This deposit consists of gravely sand to sandy gravel with some cobbles and I dominantly cemented by calcite with carbonate origin. Cemented coarse-grained soils of Tehran are heterogeneous in grading, density and cementation. Moreover, it is extremely difficult to obtain undisturbed samples to study of mechanical behavior of these soils. Therefore artificially cemented specimens with calcite were used for this mean. After determining of a base soil similar to previous study on Tehran alluvium, some triaxial specimens with 10 cm diameter and 20 cm height were prepared with 1.5, 3, 4.5 and 6 percent calcite. Calcite crystals are chemically precipitated in specimen voids helping hydrated lime and passing CO2. The samples are isotropically consolidated in six different effective confining pressures ( = 100, 300 and 500 kPa [moreover 50, 800 and 1200 kPa for 3% cement specimens]) and loading in two drainage conditions (drained and undrained). Static loading was carried out with an axial strain rate of 0.01% per minute for drained conditions and 0.005% per minute for undrained conditions. The results of study show that the tangant stiffness and shear module of calcite cemented gravely sands increase with cement content and confining pressure in two drainage conditions. With increasing cementation and decreasing confining pressure more dilative behavior in drained and undrained tests are observed. Shear strength increases with increasing cement content but the influence of the cementation decreases as the confining pressure increase. The cohesion coefficient increases with increasing cement content but internal friction angle deviation not considerable
  9. Keywords:
  10. Cemented Soil ; Calcite ; Gravely Sand ; Triaxial Test ; Static Behavior

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