3 The top 7 m at a site consists of sandy silt, having bulk unit weight (Ym) of 16.5 kN/m² and saturated unit weight (sat) of 18.5 kN/m³. The water table lies 1 m below the ground level. The sandy silt layer is underlain by a 2.5 m thick clay later (Ysat 19.5 kN/m³, average mv = 0.5 MPa ¹), which is underlain by sands. If the water table is lowered by 3 m, what would be the primary consolidation settlement of the clay layer? In solving this problem, do the following: = 1) First compute the vertical total stress, pore pressure and vertical effective stress at the mid-depth of the clay layer for the original position of the water table. 2) Next, compute the vertical total stress, pore pressure and vertical effective stress at the mid-depth of the clay layer for the case where the water table is lowered by 3 m. Note that, in the 4 m thick portion of the sandy silt above the water table, the soil will be partially saturated with Ym 16.5 kN/m³. = 3) The difference between vertical effective stress in Case 1 and Case 2 above is equal to the increment in vertical effective stress (Aσ%'%) that, along with the coefficient of volume compressibility (m₁), is used in computing the primary consolidation settlement of the clay layer. Express your answer for the ultimate primary consolidation settlement in units of millimeters.
3 The top 7 m at a site consists of sandy silt, having bulk unit weight (Ym) of 16.5 kN/m² and saturated unit weight (sat) of 18.5 kN/m³. The water table lies 1 m below the ground level. The sandy silt layer is underlain by a 2.5 m thick clay later (Ysat 19.5 kN/m³, average mv = 0.5 MPa ¹), which is underlain by sands. If the water table is lowered by 3 m, what would be the primary consolidation settlement of the clay layer? In solving this problem, do the following: = 1) First compute the vertical total stress, pore pressure and vertical effective stress at the mid-depth of the clay layer for the original position of the water table. 2) Next, compute the vertical total stress, pore pressure and vertical effective stress at the mid-depth of the clay layer for the case where the water table is lowered by 3 m. Note that, in the 4 m thick portion of the sandy silt above the water table, the soil will be partially saturated with Ym 16.5 kN/m³. = 3) The difference between vertical effective stress in Case 1 and Case 2 above is equal to the increment in vertical effective stress (Aσ%'%) that, along with the coefficient of volume compressibility (m₁), is used in computing the primary consolidation settlement of the clay layer. Express your answer for the ultimate primary consolidation settlement in units of millimeters.
Fundamentals of Geotechnical Engineering (MindTap Course List)
5th Edition
ISBN:9781305635180
Author:Braja M. Das, Nagaratnam Sivakugan
Publisher:Braja M. Das, Nagaratnam Sivakugan
Chapter9: Consolidation
Section: Chapter Questions
Problem 9.8P
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The top 7 m at a site consists of sandy silt, having bulk unit weight (Ym) of 16.5 kN/m²
and saturated unit weight (sat) of 18.5 kN/m³. The water table lies 1 m below the ground
level. The sandy silt layer is underlain by a 2.5 m thick clay later (Ysat
19.5 kN/m³,
average mv = 0.5 MPa ¹), which is underlain by sands. If the water table is lowered by 3 m,
what would be the primary consolidation settlement of the clay layer?
In solving this problem, do the following:
=
1) First compute the vertical total stress, pore pressure and vertical effective stress at the
mid-depth of the clay layer for the original position of the water table.
2) Next, compute the vertical total stress, pore pressure and vertical effective stress at the
mid-depth of the clay layer for the case where the water table is lowered by 3 m. Note that,
in the 4 m thick portion of the sandy silt above the water table, the soil will be partially
saturated with Ym 16.5 kN/m³.
=
3) The difference between vertical effective stress in Case 1 and Case 2 above is equal to
the increment in vertical effective stress (Aσ%'%) that, along with the coefficient of volume
compressibility (m₁), is used in computing the primary consolidation settlement of the clay
layer. Express your answer for the ultimate primary consolidation settlement in units of
millimeters.
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