Geotechnics

Assignment-1:

Q1)  The classification of the soil is as follows:

• Soil A- Well graded gravel. The soil A consists of the inorganic clays of the varying plasticity. It also consists of the clays from the sandy to gravel. The plastic limit(PL) of the soil is 8.2 and the liquid limit(LL) of the soil is 35.
• Soil B- clayey gravel with sand. The soil B consists of the poorly graded soil which consists of the inorganic clays and also has high plasticity.

By analyzing the Grain size distribution curve,

Cu = D60/D10 = 0.72/0.19 = 3.79 and Cc= (D30)2/ (D60×D10) = (0.35)2/(0.72×0.19) = 0.1225/0.1368 = 0.895. thus it can be said that the Soil is SP category soil type.

• Soil C- Well graded soil with silt and sand. This is a fine grained soil which comprise of the silts which are mostly inorganic and have very low plasticity. The soil belongs to OL-CL.

Q2)  

Given data:

Dimensions- Diameter=50mm and Length=100 mm

Initial mass of sample= 336.5g

Mass of the sample after drying=292.6g

Packing of the soil in the borrow area = 13kn/m3

Packing of the soil in the fill area= 11 kn/m3 

Thus it can be said that the solid particles are more densely packed in the trench.

Therefore 1m3 of the compacted fill occupy volume= 11/13 = 0.846 m3.

Thus the required volume to be excavated = 75*0.846= 63.45m3.

Q3)

(a)

According to the information provided in the question the data given is as follows:

Sc = Consolidation Settlement

 Cc = Compression Index= 0.495

 e0 = Initial Void Ratio = 0.65*2.7=1.755

H = Thickness of clay layer = 4 m

σ0 = Initial overburden pressure at the middle of clay layer = 150KPa

Δσ = Extra pressure due to the new construction = 46KPa

Thus the required formula is as follows:

[pic 1]

Sc= 0.7186 *log10(1.30)

Sc = 0.7186*0.114

Sc= 0.0818 m

Hence the thickness of the clay layer is 0.0818m.

(b) Sc = Consolidation Settlement

 Cc = Compression Index= 0.495

 e0 = Initial Void Ratio = 0.65*2.7=1.755

H = Thickness of clay layer = 4 m

σ0 = Initial overburden pressure at the middle of clay layer = 150KPa

Δσ = Extra pressure due to the new construction = 46KPa

[pic 2]

S= -0.36881+0.818 = -0.28, the negative sign shows that the clay is overconsolidated.

Assignment 2:

Q1)

1. The overall factor of safety of the wall against the sliding:

(F)= Resisting forces/Disturbing Forces