TEST PAPER

1)A). Liquid Limit It is one of the atterberg limit. It is the water content at which soil (clayey ) behaviour changes from Plastic To Liquid. At this limit there is very small shear strength in the soil & it keeps on decreasing with increase in water content.We can also say that boundary water content between Plastic state & Liquid state is called Liquid Limit.Practically it is the water content at which a groove cut out of soil by a grooving tool of std dimensions will flow together for a distance of 13 mm under the impact of 25 blows.b). Plasticity Index It basically shows plasticity of the soil. It shows the range over which soil shows plasticity. It shows degree of plasticity of soil.Mathematically , we can say that it is the difference between Liquid Limit & Plastic Limit.Soil having high value of PI is Clay, Low value of PI is Silt.Coarse grained soils have PI = 0.c). Void Ratio It is defined as the ratio of volume of voids to volume of solids.If void ratio is high (loose soils) voids in a soil skeleton tend to minimize under loading - adjacent particles contract. The opposite situation, i.e. when void ratio is relatively small (dense soils), indicates that the volume of the soil is vulnerable to increase under loading - particles dilate.

d). Sensitivity It is defined as the ratio of unconfined compressive strength of an undisturbed specimen of the soil to the unconfined compressive strength of a specimen of same soil after remoulding at unaltered water content.2) Compaction : Reduces volume of soil by rapid mechanical methods.Consolidation : reduction in volume by static loading. Compaction : decrease in volume by expelling air from partially saturated soil.Consolidation : volume reduction by squeezing out of water from saturated soil. Compaction : it is a human generated pressing method.Consolidation : it is a natural method. Compaction : it is immediate process.Consolidation : it takes more time than compaction.

b) Liquefaction : 1. There is sudden decrease in shear strength due to applied stress.2. occurs due to vibrations such as Earthquake shaking or sudden change in stress condition.3. observed in loose, saturated soil.Quick Sand Condition : 1. forms when water saturates an area of loose sand and the ordinary sand is agitated.2. it can be formed by standing or flowing water or earthquake.3. occurs in fine sand.

3). Gross Allowable bearing pressureQg = Qc + (B^2)*Dc*Yc + (B^2)(Df Dc)*YWhere,Qg = gross allowable bearing pressureB = width of footingDc= depth of concreteYc = unit wt of concreteDf= depth of footingY = unit wt of soil

Net Allowable bearing pressureQn = Qg Y*DfQn = Qc + (B^2)*Dc*Yc + (B^2)(Df Dc)*Y Y*Df

8). Different methods of soil improvement are : Adjust the soil pH to optimal levels (6-7)- general (nutrient availability) Applying compost/aged manure- nitrogen, carbon, moisture, soil biota (bacteria/fungi), general (structure/nutrients) Natural mineral fertilizers- general (minerals/nutrients) Deep mulching- carbon, moisture, soil biota (fungi) After initial incorporation of amendments, no tillage or compaction- general (structure), moisture, soil biota Living mulches, Cover-cropping with legumes/deep-rooted plants- nitrogen, carbon, moisture Biotic innoculants- soil biota (bacteria/fungi), general (structure) Soil stabilising methods1)Mechanical stabilisation:.2)Chemical stabilisation3) lime stabilisation: 4)bitumen stabilisation:5)cement stabilisation

1.Adjust the soil pH to optimal levels (6-7)- general (nutrient availability) The pH of soil dictates the ability of plants to absorb nutrients. Many plants thrive with a pH between 6 and 7 but acid loving plants, prefer a pH of less than 6. A soil sample can help you identify your current soil pH. Adding lime (to raise the pH) or sulfur (to lower the pH) prior to any planting will make itmore effectiveand easierto adjust the pH.2. After initial incorporation of amendments, no tillage or compaction- general (structure), moisture, soil biota Initial tilling to incorporate our previously mentioned approaches to soil building and to breakup hard, compacted ground may benecessary, but after that it should be avoided. Tilling can produce a number of negative effects including soil compaction under the tines, excess breakdown of soil carbon, the destruction of soil life (worms and fungus in particular), and the disruption of the soil structure/profile. Compaction of the soil due to stepping on it can also negatively impacts soil health. If tilling is needed to create a nice seedbed, make sure you vary the depth of the tilling year after year and never till when the soil is very wet or very dry.

5).plate load testIt is a field test for determining the ultimate bearing capacity of soil. In this test a plate of 75 cm dia is used. If the subgrade modulus is needed then the top soil may be removed for 20 cm before testing. A pressure of 0.075 kg/cm^2 is applied & released after a few second, & continuosly the deformation reading is noted down with the help of dial gauge. Three dial gauges are placed at an angle of 120 degree to each other.The test load is gradually increased till the plate starts to sink at a rapid rate. The total value of load on the plate in such a stage divided by the area of the steel plate gives the value of the ultimate bearing capacity of soil. The ultimate bearing capacity of soil is divided by suitable factor of safety (which varies from 2 to 3) to arrive at the value of safe bearing capacity of soil.

7).Static methodCohesive soilQup = 9cAb + acAsWhere, A = adhesion factor of pile soilAb = bearing area of pileAs= Surface area of pile in contact with soilc = undrained cohesion at the base of pilec = undrained cohesion in the embedded length of pile

cohesionless soilQpu = k*a*tan b *As + qb * AbWhere,k = lateral earth pressure coefficienta = avg effective overburden pressureb= angle of friction between pile & soilqb= unit bearing resistance

6).givenH= 7 mWater content=0.405liquid limit =48%G=2.76Cc= 0.009(wl- 10) = 0.342for clay layerSr=1 e=wG= 0.405x2.76=1.1178sub= (G-1)x w/(1+e)= (2.76-1) x 10/2.1178= 8.3105Kn/m2 = 120 KN/m2 ' at middle of clay layer = 18x5 + 11x7+ 8.3105x3.50 =196.067 KN/m2as we have the formula, H= (H x Cc/(1+e)) x Log10[(0 + )/0 ]= (7 x 0.342/2.1178) x Log10 ( 1.6111)= 0.23 m

4). Mechanism of reinforced soil in resisting forces in a retaining wall An externally stabilized system uses an external structural wall against whichstabilizing forces are mobilized. An internally stabilized system involves reinforcementsinstalled within the retained soil mass and extending beyond the potential failure plane.Hybrid systems combine elements of both internally and externally supported walls.It is in the area of internally stabilized systems that relatively new concepts have been introduced. Shear transfer to mobilize the tensile capacity of closely spaced reinforcing elements embedded in the retained soil mass has enabled retaining structures to be constructed without an external structural wall element. The shear transfer mechanism allows a composite system of reinforcing elements and soil to serve as the primary structural entity. A facing is required on an internally stabilized system, however, its purpose is to prevent raveling and deterioration rather than to provide primary structural support.Materials used are : Geocells, Geogrids, Geoform, Geocomposites, Geotextiles.Construction MethodEarth retaining structures (ERS) can also be classified according to the method required for their construction.1.fill construction2.cut construction Fill wall construction refers to a wall system in which the wall is constructed from the base of the wall up to the top, i.e., bottom-up construction. Cut wall construction refers to a wall system in which the wall is constructed from the top of the wall down to the base concurrent with excavation operations,The cut and fill designations refer to how the wall is constructed, not necessarily the nature of the earthwork associated with the project. Forexample, a prefabricated modular gravity wall, which may be used to retain earth for a majorhighway cut, is considered a fill wall because its construction is not complete until the backfill has been placed from the bottom-up after the excavation for the cut has reached its final grade.