MEKANIKA TANAH 1

1. MEKANIKA TANAH 1 PERTEMUAN VI Effective Stress Theory Oleh : Arwan Apriyono PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED TAHUN 2011

2. Introduction All the measurable effects of a change of stress, such as compression, distortion and a change in the shearing resistance are exclusively due to changes in effective stress… every investigation of the stability of a saturated body of earth requires the knowledge of both the total and the neutral stresses (Terzaghi, 1936)

3. Introduction “The loss of weight of a body submerged in water is equal to the weight of water displaced, and that a floating body displaces its own weight of water.” Archimedes (287-212 BC)

4. Concept • Soil is a multi phase system • To perform any kind of analysis - we must understand stress distribution • The concept of soil stress: • The soil is “loaded” (e.g. footing, own weight of soil) • The resulting stress is transmitted to the soil mass • The soil mass supports those stresses at the point to point contacts of the individual soil grains

5. Concept This total stress can be visualized to consist of TWO components the pressure upon the soil skeletal component, called the effective stress 'and, the pressure from the water component in the voids continuum, called the pore water pressure u, also known as the neutral stress.

6. Equation Where g'= gsat- gwis the buoyant or submerged unit weight of soil.

7. Example

8. Example

9. Example Plot the variation of total and effective vertical stresses, and pore water pressure with depth for the soil profile shown below

10. Example

11. Example