The soil profile at a site for a proposed office building consists of a layer of fine sand 10.6 m thick above a layer of soft, normally consolidated 2.2 m thick clay layer in the manner shown in Figure 3. Underlying the clay is a layer of stiff coarse sand. The groundwater table was observed to be at a depth of 3.2 m below ground level. The soil above the ground water table is assumed to be saturated. applied surface load Fine sand layer Clay layer 3.2 m 10.6 m 2.2 m Coarse sand Figure 3: Schematic illustration of soil profile at a proposed office building site. Laboratory tests indicate that the void ratio (e) for the sand is equal to 0.758 and that the specific gravity of solids (Gs) is 2.67. The fine sand above the groundwater table is saturated due to capillarity. The moisture content (w) of the clay layer is 43%. Its liquid limit (LL) is 45%, and Gs is 2.70. Please do the following: a) First compute the unit weights of the sand and clay layers. b) Next compute the vertical effective stress at the mid-depth of the clay layer. c) Consider the empirical expression proposed by Terzaghi and Peck [3]; i.e., C = 0.009(LL 10) where LL represents the liquid limit, entered as a percent. Determine the maximum vertical effective stress increase (Aσ% = Aσ2) that the building can impose on the middle of the clay layer so that the primary consolidation settlement (sc) does not exceed 90 mm. d) For the same limiting value of sc, what would be the maximum vertical effective stress increase that the building can impose on the middle of the clay layer if, instead, the empirical expression proposed by Azzouz et al. [1] is used instead; i.e., C=0.40(eo-0.25) e) Finally, repeat part (d) using the empirical expression proposed by Nagaraj and Srini- vasa Murthy [2]; i.e., C=0.00234(LL) (GS) where LL again represents the liquid limit, entered as a percent. Which of the three above empirical expressions yields the most conservative value of Δσο, = Δσι?

The soil profile at a site for a proposed office building consists of a layer of fine sand 10.6 m thick above a layer of soft, normally consolidated 2.2 m thick clay layer in the manner shown in Figure 3. Underlying the clay is a layer of stiff coarse sand. The groundwater table was observed to be at a depth of 3.2 m below ground level. The soil above the ground water table is assumed to be saturated. applied surface load Fine sand layer Clay layer 3.2 m 10.6 m 2.2 m Coarse sand Figure 3: Schematic illustration of soil profile at a proposed office building site. Laboratory tests indicate that the void ratio (e) for the sand is equal to 0.758 and that the specific gravity of solids (Gs) is 2.67. The fine sand above the groundwater table is saturated due to capillarity. The moisture content (w) of the clay layer is 43%. Its liquid limit (LL) is 45%, and Gs is 2.70. Please do the following: a) First compute the unit weights of the sand and clay layers. b) Next compute the vertical effective stress at the mid-depth of the clay layer. c) Consider the empirical expression proposed by Terzaghi and Peck [3]; i.e., C = 0.009(LL 10) where LL represents the liquid limit, entered as a percent. Determine the maximum vertical effective stress increase (Aσ% = Aσ2) that the building can impose on the middle of the clay layer so that the primary consolidation settlement (sc) does not exceed 90 mm. d) For the same limiting value of sc, what would be the maximum vertical effective stress increase that the building can impose on the middle of the clay layer if, instead, the empirical expression proposed by Azzouz et al. [1] is used instead; i.e., C=0.40(eo-0.25) e) Finally, repeat part (d) using the empirical expression proposed by Nagaraj and Srini- vasa Murthy [2]; i.e., C=0.00234(LL) (GS) where LL again represents the liquid limit, entered as a percent. Which of the three above empirical expressions yields the most conservative value of Δσο, = Δσι?

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 9.20CTP

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