Proceedings of Indian Geotechnical Conference December 15-17,2011, Kochi (Paper No.J-049 ) BEHAVIOUR OF GEOSYNTHETIC REINFORCED SAND BED UNDER CYCLIC LOAD M.V.S. Sreedhar, Assistant professor, Osmania University, Hyderabad-500007. E-mail: [email protected]A. Pradeep Kumar Goud,M.EStudent, Osmania University, Hyderabad-500007. E-mail: [email protected]ABSTRACT: An attempt was made in this project to investigate the static and cyclic behaviour of Sand reinforced with geosynthetic products by conducting load tests in a large size tank of 1200 x1200 x900 mm internal dimensions. The static behavior was ascertained in terms of “Bearing Capacity Ratio (BCR)” and the dynamic response in terms of ‘Coefficient of Uniform Compression, Cu’. The sand bed of 500mm thick was compacted at a relative density of 90% in dry state and is reinforced with four geosynthetic products viz., Polymeric Woven Geotextile, uni-axial geogrids of two different capacities and a coir geotextile. The size, shape, depth of placement and the surcharge were maintained same. A square model footing of 100mm size was used as the loading unit. Static and Cyclic Plate Load tests are carried out separately on unreinforced sand and sand reinforced with each type of geosynthetic product. The results indicated that, the geosynthetic products with higher mobilized tensile strength have shown better improvement in BCR and Cu values. Based on the results, within the scope of this project, a mathematical model was constituted for prediction of BCR and Cu values. INTRODUCTION The infrastructure development in India has tremendously increased the applications of geo-synthetics in the areas of pavements, retaining walls, solid waste disposal etc. The design philosophies are mainly based on the behaviour of reinforced earth subjected to static loads. However, all these structures are prone to cyclic loads due to an earth quake, traffic load, machine foundations etc. It is therefore necessary to understand the behaviour of geosynthetic reinforced soil subjected to cyclic loads. LITERATURE REVIEW Limited research was done on studying the behaviour of reinforced sand under cyclic loading. A.K.Verma and Bhatt (2008),[1] have studied behaviour of reinforced sand under cyclic loading. They reported that the reinforced sand has more damping capacity than that of unreinforced sand bed and the percentage damping capacity decreases with increase in load intensity. Shvets and Nazha (2000),[2] investigated the influence exerted by anisotropy of the deformation properties of soil foundation beds on the elastic characteristics used in dynamic analyse of machine-bearing foundations. They suggested that correction factors dependent on the degree of anisotropy of the soil, which should be used in the analyses. STATEMENT OF THE PROJECT The objective, necessity and scope of this project are as given below Objective The primary objective of this project is to determine the bearing capacity and coefficient of elastic uniform compression of geosynthetic reinforced sand by conducting static plate load test, cyclic plate load test respectively. And the objective includes the determination intersurface friction between sand and geosynthetics based on pull out test. Necessity The design of machine foundation based on Cu , it is related to remaining properties. Cu can be improved with geosyntheic reinforced material. Having higher the Cu value, resilience is enhanced. Scope Scope of the project is bounded to the observing the mechanism in macroscopic level in terms of pressure and settlement. Static , cyclic plate load test and pull out tests are conducted using one type of sand and four types of geosynthetics. METHODOLOGY The methodology includes the Collection and characterisation on sand Collection and characterisation of geosynthetics Experimental programme. Collection and characterisation on sand The sand was used in this project collected from Krishna River, Andhra Pradesh. The engineering properties of the sand were as shown in Table. 1 Table 1 Properties of sand Property Value Specific gravity 2.52 MDD (kN/m 3 ) 1650 OMC (%) 13.6 Cu 4.11 Cc 1.27 Classification of sand SP 519
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Proceedings of Indian Geotechnical Conference December 15-17,2011, Kochi (Paper No.J-049 )
BEHAVIOUR OF GEOSYNTHETIC REINFORCED SAND BED
UNDER CYCLIC LOAD
M.V.S. Sreedhar, Assistant professor, Osmania University, Hyderabad-500007. E-mail: [email protected]
A. Pradeep Kumar Goud,M.EStudent, Osmania University, Hyderabad-500007. E-mail: [email protected]
ABSTRACT: An attempt was made in this project to investigate the static and cyclic behaviour of Sand reinforced with
geosynthetic products by conducting load tests in a large size tank of 1200 x1200 x900 mm internal dimensions. The static
behavior was ascertained in terms of “Bearing Capacity Ratio (BCR)” and the dynamic response in terms of ‘Coefficient of
Uniform Compression, Cu’. The sand bed of 500mm thick was compacted at a relative density of 90% in dry state and is
reinforced with four geosynthetic products viz., Polymeric Woven Geotextile, uni-axial geogrids of two different capacities
and a coir geotextile. The size, shape, depth of placement and the surcharge were maintained same. A square model footing
of 100mm size was used as the loading unit. Static and Cyclic Plate Load tests are carried out separately on unreinforced
sand and sand reinforced with each type of geosynthetic product. The results indicated that, the geosynthetic products with
higher mobilized tensile strength have shown better improvement in BCR and Cu values. Based on the results, within the
scope of this project, a mathematical model was constituted for prediction of BCR and Cu values.
INTRODUCTION
The infrastructure development in India has tremendously
increased the applications of geo-synthetics in the areas of
pavements, retaining walls, solid waste disposal etc. The
design philosophies are mainly based on the behaviour of
reinforced earth subjected to static loads. However, all
these structures are prone to cyclic loads due to an earth
quake, traffic load, machine foundations etc. It is therefore
necessary to understand the behaviour of geosynthetic
reinforced soil subjected to cyclic loads.
LITERATURE REVIEW Limited research was done on studying the behaviour of
reinforced sand under cyclic loading. A.K.Verma and Bhatt
(2008),[1] have studied behaviour of reinforced sand under
cyclic loading. They reported that the reinforced sand has
more damping capacity than that of unreinforced sand bed
and the percentage damping capacity decreases with
increase in load intensity.
Shvets and Nazha (2000),[2] investigated the influence
exerted by anisotropy of the deformation properties of soil
foundation beds on the elastic characteristics used in
dynamic analyse of machine-bearing foundations. They
suggested that correction factors dependent on the degree
of anisotropy of the soil, which should be used in the
analyses.
STATEMENT OF THE PROJECT
The objective, necessity and scope of this project are as
given below
Objective
The primary objective of this project is to determine the
bearing capacity and coefficient of elastic uniform
compression of geosynthetic reinforced sand by conducting
static plate load test, cyclic plate load test respectively. And
the objective includes the determination intersurface
friction between sand and geosynthetics based on pull out
test.
Necessity
The design of machine foundation based on Cu , it is
related to remaining properties. Cu can be improved with
geosyntheic reinforced material. Having higher the Cu
value, resilience is enhanced.
Scope
Scope of the project is bounded to the observing the
mechanism in macroscopic level in terms of pressure and
settlement. Static , cyclic plate load test and pull out tests
are conducted using one type of sand and four types of
geosynthetics.
METHODOLOGY
The methodology includes the
Collection and characterisation on sand
Collection and characterisation of geosynthetics
Experimental programme.
Collection and characterisation on sand
The sand was used in this project collected from Krishna
River, Andhra Pradesh. The engineering properties of the
sand were as shown in Table. 1 Table 1 Properties of sand
Property Value
Specific gravity 2.52 MDD (kN/m3) 1650 OMC (%) 13.6 Cu 4.11 Cc 1.27 Classification of sand SP
519
M.V.S.Sreedhar & A.Pradeep Kumar Goud.
Angle of shear resistance at 90% RD
410
Collection and characterisation of geosynthetics
Total four types of geosynthetics were used in this work.
The properties of all productes were shown in Tables 2 - 5.