CBR Values Test

CBR Values Test

INTRODUCTION:

            Three Soil sample has supplied for investigation to ascertain the physical and engineering properties along with proctor value and CBR values table for the purpose of construction.

 

OBJECTIVE:

            This report describes the finding of sub-soil investigation and laboratory tests conducted on these soil samples and the data required for purpose.

 

 

LABORATORY INVESTIGATION:

For proper identification & classification of the sub-soil strata and for deriving adequate information regarding its relevant Geo-technical properties of the site under investigation, the following laboratory tests were conducted on the soil samples collected from boreholes-

 

v  GRAIN SIZE ANALYSIS AS PER IS: 2720, part-IV

·         SIEVE ANALYSIS

The  complete  sieve  analysis  can  be  divided  into  two parts,  i.e,  the  coarse  analysis  and  fine analysis. An oven dried samples of soil is separated into two fractions by sieving it through a4.75 mm IS sieve. The portion retained of it (+4.75mm size) is termed as the gravel fraction and  is  kept  for  the  coarse  analysis,  while  the  portion  passing  through  it  (-4.75mm  size)  is subjected to fine sieve analysis.

 

·         HYDROMETER ANALYSIS

In  the  wet  method  of  mechanical  analysis  or  sedimentation  analysis,  the  soil  fraction,  finer than 75 micron size is kept in suspension in a liquid (usually water) medium. The analysis is based on stake's law, according to which the velocity at which grains settle out of suspension, all  other  factor  being  equal,  is  depended  upon  the  shape,  weight  and  size  of  the particles/grains

v  SOIL CONSISTENCY AS PER IS: 2720, part-V

These  are  arbitrary  moisture  contents  to  determine  the  instant  at  which  the  soil  is  on  the verge of being viscous liquid (Liquid limit) or non–plastic /Plastic limit. Liquid limits determined with the help of a liquid limit apparatus. Plastic limit is the water content at which the soil begins to crumble when rolled out into a thin thread of 3mm

 

v  MOISTURE CONTENT AS PER IS: 2720, part-IX

It is the ratio of the weight of water to the dry weight of soil determined by oven drying

 

v  DRY DENSITY AND BULK DENSITYAS PER IS: 2720, part-IX

These  were  determined  by  measuring  the  weights  and  dimensions  of  tri-axial  shear  and unconfined compressive strength test samples before testing and after oven drying. The bulk density & dry density values of the samples have been given in the enclosed laboratory sheet.

 v  SPECIFIC GRAVITY AS PER IS: 2720, part-III

The Specific Gravity of the soil samples was determined by adopting standard procedure. The soil sample was dried in oven dried for 24 hours and pulverized. The sample was then poured into a specific gravity bottle and topped up with distilled water. The specific gravity bottle was stirred and heated to eliminate air bubbles.  The weight of the specific gravity bottle was recorded along with the temperature of the sample.

 

v  DETERMINATION OF C.B.R VALUE:

Three(03) nos. of samples has supplied from construction area by the client to find out the proctor density and CBR value.

 

·         PROCTOR TEST & CALIFORNIA BEARING RATIO TEST (CBR):

Proctor test is done by using standard proctor mold. Dried soil sample mixed with small quantity of water is kept in the mold and compacted by using standard rammer in three layer with 25 blows on each layer and weight , moisture content are taken. This process is repeated with increasing quantity of water till weight is decreases. After plotting the reading in the graph get the OMC and Maximum dry density.

 

For CBR test the sample are compacted in CBR mold and kept under water for 96 hours in soft condition. Later on it is tested on CBR apparatus. The load readings are recorded at penetration 0.00mm, 1.00mm, 1.50mm, 2.00mm, 2.50mm, 3.00mm, 4.00mm, 5.00mm, 7.50mm, 10.00mm and 12.50mm. The penetration curves are plotted in graph and CBR value is calculated for penetration of 2.50mm, 5.00mm and 7.50mm.

BRIEF DESCRIPTION AND CLASSIFICATION OF THE SOIL SAMPLE:

The borehole log and particle size distribution curves reveal the following underlying sub-soil strata as per IS: 1498 specification below the investigation area-

 

Sample –I/SS-I:

Brownish to Greyish/light greyishcolouredsilty clay, impervious, low compressibility, sticky, medium plasticity, low compressibility, impervious layer, fair to moderate in consistency, traces of non-plastic silt, saturated, inorganic, cohesive soil

 

Sample-II/SS-II:

Light Brownish Ash/light Brownish colouredpoorly graded sand mixed with non-plastic silt, traces of non-plastic silt and dust mica and clay binder in some layer, fairly moderate to dense in compactness, inorganic, cohesion less soil

 

 GRAIN SIZE DISTRIBUTION & SOIL CONSISTENCY PARAMETER

(As per IS: 2720, Part-IV&Part-V)

Sample No	Particle Size Distribution					Atterberg Limits			Shrinkage Limit	Free swelling Index (%)	Permeability (cm/Sec)
	Clay	Silt	Sand	Gravels	IS Classification	Liquid limit (%)	Plastic limit (%)	Plastic Index (%)
SS-I	21.00	64.00	15.00	0.00	CI	38.4	24.1	14.3	---	10.91	---
SS-II	4.00	49.00	47.00	0.00	SM	---	---	---	---	---	---

 

 

MOISTURE CONTENT, DENSITIES, SPECIFIC GRAVITY VOID RATIO, SHEAR & CONSOLIDATION PARAMETERS

(As per IS: 2720, Part-III &Part-IX, Part-XI, Part-XII, Part-XIII & Part-XV)

Sample No	In-Situ Properties of Soil					Shear parameter		Consolidation parameter		U.C.C in t/m2
	Moisture Content in %	Bulk Density in t/m3	Dry Density in t/m3	Specific Gravity	VoidRatio	Cohesion in t/m2	f in degree	Cc	Av
SS-I	19.026	1.934	1.625	2.619	0.612	---	---	---	---	---
SS-II	14.602	1.929	1.683	2.630	0.562	---	---	---	---	---

 

 

PROCTOR COMPACTION TEST& CALIFORNIA BEARING RATIO TEST (CBR)

 

Sample No	Sand Content In %	Proctor Test			CBR Test		CBR Value In %	Average CBR value In %
		O.M.C In %	M.D.D In gm/cc	Proctor value	2.5mm Penetration	5.0mm Penetration
SS-I	15.00	18.65	1.74	91.8%	4.69	4.09	4.69	---
SS-II	47.00	15.0	1.76	94.5%	5.35	4.66	5.35	---

SUITABILITY OF EXISTING SOIL FOR FILLING PURPOSES:

Having seen the engineering properties of these soils,we shall now assess their suitability as backfilling as follows-

 

·         Sample No-2 (SS-II),Soil is generally fine sand mixed with non-plastic silt and swelling characteristics does not arise. The compaction test results performed on selected supplied soil samples indicate the maximum dry density value 1.76gm/c3 and optimum moisture contents varying between 15.0%. CBR tests were carried out at the optimum moisture contents and maximum dry density obtained from the compaction tests performed. The CBR values at 2.5 mm penetration vary from 4.66% to 5.35%.The CBR test results indicate that in-situ soil is having good compaction properties for the sub-grade. Based on soil properties, this soil is recommended for as good for earth filling all type construction.

·         Sample No-1 (SS-I), Soil is generally fine silty clay mixed with non-plastic silt and swelling characteristics under marginal value. The compaction test results performed on selected supplied soil samples indicate the maximum dry density value 1.74gm/c3 and optimum moisture contents varying between 1865%. CBR tests were carried out at the optimum moisture contents and maximum dry density obtained from the compaction tests performed. The CBR values at 2.5 mm penetration vary from 4.09% to 4.69%.The CBR test results indicate that in-situ soil is having fairly good compaction properties for the sub-grade. Based on soil properties, this soil is recommended for as fairly good for earth filling all type construction