Civil Engineering Application of JGT
 

Civil Engineering Applications of JGT 

  1. Slope Management with JGT

  2. Protection of River Banks

  3. JGT in Road Construction

  4. Stability of Embankments

 
  1. Prevention of Railway Track Subsidence

  2. Consolidation of soft soil

  3. Control of surface soil detachment

 

i. Slope Management with JGT  

   

Slopes erode due to: 

  • Overland flow

  • Severe wind

 

The resultant erosion can be controlled by reducing the velocity of surface run-off and partial containment of detached soil particles. 

Open weave JGT with 3D construction controls slope erosion  by 

  • Creating an array of micro-barriers against the overland flow, thus reducing its velocity. 

  • Effecting partial storage due to capacity jute to absorb water (hygroscopicity of jute) 

  • Entrapping detached soil particles.

  • Absorbs water up to about 5 times its dry weight  
    (N.B. - 500 gsm JGT having a thickness of 4 mm  with 45 wefts / meter can store  0.44 litres per sqm of water on 1: 2 slope)  

  • Promotes quick growth of vegetation.

 

ii. Protection of River Banks    

 

JGT has been successfully tried to control river bank erosion if there is no strong hugging current or vortices at the bank-toe. 

The conventional practice of using granular filter as a bank protective cover suffers from certain disadvantages :  

  • No separation between  layers resulting in inter-penetration of layers

  • Reduction in design thickness of  layers due to interpenetration

  • Impairment of Permittivity Fabric Filter

Problems of conventional practice 

  • Availability of the right filter materials in time.

  • Control on quality and workmanship.

  • Time of execution.

  • Environmental  concerns due to quarrying/mining for filter materials.

Therefore  a need for an economical and effective substitute. JGT is an effective eco-friendly substitute and makes room for bo-engineering support through vegetation-growth after its degradation.

JGT, a natural fabric filter, is  an effective substitute of conventional granular filter. It can satisfy all the requirements of filter needed  for protection of river banks. 

  • In unidirectional flow - 2 season cycles are sufficient  for filter-cake formation & natural stability

  • In flow – reversals -  with a moderate cycle time, a longer time is needed ( > 4 season – cycles )

Survivability of JGT depends on--   

  • Careful storage, handling, transportation,   laying on level surface 

  • Guarding against puncture by falling   aggregates  

  • Avoiding soil-slurry at the time of laying

 

iii. JGT in Road Construction 
     

How can JGT help?  

  • Enhances the CBR  of the sub grade 

  • Prevents intermixing of sub-grade and sub-base 

  • Facilitates filtration & drainage in the sub-surface zone

 

 

Woven JGT should be selected in conformity with the average particle size distribution of the sub grade, the required tensile strength and hydraulic conductivity of the soil

Provisions of sub-surface drainage should be made with non-woven JGT concurrently. 

Note : Choice of JGT also depends on the allowable rut  depth which is a factor of the level of service expected of a road vis-à-vis the level of its maintenance 

iv. Stability of Embankments 

Oven JGT when used as a basal layer and interposed in layers within an earthen environment can prevent/control  

  • Vertical subsidence / settlement

  • Lateral dispersion

  • Down-slope migration

  • Rotational slides (slip circle failure)

Why JGT is effective ? 

  • JGT absorbs stress and strain induced due to moving loads on embankments

  • Soil - JGT friction acts as a medium of transference of the induced  stress and strain

  • JGT can directly reinforce the soil mass in an embankment during its useful lifespan

  • Soil is otherwise stabilized due to separation, filtration and drainage functioning concurrently

Basal reinforcement with JGT for any new embankment is  effective
JGT can also be used in successive layers of an embankment and may be folded at the fringes for side restraint. Such arrangement can prevent slips/slides 

Precaution

Care should be taken to ensure prevention of ingress of water into an embankment. Drain out entrapped water from an embankment for which JGT encapsulated concealed drains may be installed. 

v. Prevention of Railway Track Subsidence 

JGT has proved effective in controlling settlement of railway tracks also. It has been tried with success in sections under Howrah-Burdwan Cord line in Eastern Railways, India. 

Causes of railway track subsidence 

  • Erosion pumping

  • Intermixing of ballast and sub-grade

  • Entrapped water within embankment

  • Surficial erosion à erosion of cess width Solution

Remedial Procedure

  • Use of JGT (woven + non-woven) on sub-grade after removal of ballast layer

  • Use of JGT encapsulated rubble drains within   embankment

  • Reshaping of embankment profile – rebuilding the cess

  • Protection of slope with open mesh JGT

  • Vegetation on slope

vi. Consolidation of soft soil 

Pre-fabricated Vertical Jute Drains (PVJD) has been found effective in consolidating soft soil. Prof. S. D. Ramaswamy has patented a type of PVJD with Hessian sheath and coir. IIT, Delhi  under Prof. P. K. Banerjee has developed a PVJD with braided sheath 

PVJD is a 

  • Better substitute of sand - drains

  • Drains out water by capillary action

  • Standard prefab vertical jute drains with  jute/coir wicks available

  • Equivalent drain diameter and its zone of influence may be calculated (as per Runesson et al,1977) to determine the drain-spacing

vii. Control of surface soil detachment 

JGT  

  • Makes soil more erosion-resistant

  • Attenuates extremes of temperature

  • Protects soil and seeds from direct exposure

  • Controls dehydration of soil

  • Allows air and light

  • Adds nutrients to the soil and acts as mulch on biodegradation

JGT promotes growth of vegetation as bio-engineering support 

Vegetation in turn 

  • Dissipates KE of rain drops 

  • Is a receptor of moisture

  • Attenuates wind effects

  • Reduces velocity of surface run off

  • Ensures soil attachment with roots

  • Improves soil – permeability

Choice of vegetation is important 

JGT 

  • Improves micro-climatic conditions  

  • Enhances organic matter levels 

  • An excellent catalyst for quick growth of vegetation