Case Studies

PAVEMENT SUBSURFACE DRAINAGE USING GEOCOMPOSITE, AGARTALA

KMC Constructions Limited
Tripura

This case study discusses the possible causes of flexible pavement failureswith poor subsurface drainage under high infiltration and capillary rise conditions, recommends TechDrain Drainage Composite for subsurface drainage instead of conventional gravel drainage.

Special Accelerated Road Development Programme for North East (SARDP-NE) for North Eastern Region and Sikkim is a specially designed high way development programme for the North Eastern region.Ministry of Road Transport and Highways has formulated SARDP – NE for enhancing road facilities in the North-East region.TechDrain Drainage Composite –1,80,000Sqm

Improvement/ Widening to two laning with paved shoulder of Agartala Udaipur section from km 6.800 to 55.000 of NH 44 under SARDP-Phase A, in the state of Tripura

Keywords

    TechDrain Drainage Composite –1,80,000Sqm

Introduction

Objectives of the scheme are up-gradation of National Highways connecting State Capitals with 2 lane or 4 lane roads.Under This project NH 44 was planned to be improved to a two lane road from km 6.800 to 55.000.

There were some major challenges to achieve the objectives as the availability of aggregate for construction of pavement structure was scarce and even the available resources were of marginal quality.

The state of Agartala is one of the high rainfall area and performance of pavement majorly depends on the effective drainage of infiltered subsurface water out of the pavement layers.

test.

Problem Description

The detrimental effects of water in the pavement system are significant. AASHTO (1993)reports:

  • Water in the asphalt surface can lead to moisture damage, modulus reduction andloss of tensile strength. Saturation can reduce the dry modulus of the asphalt byas much as 30 percent or more.
  • Added moisture in unbound aggregate base and subbase is anticipated to result ina loss of stiffness on the order of 50 percent or more.
  • Modulus reduction of up to 30 percent can be expected for asphalt-treated baseand increase erosion susceptibility of cement or lime treated bases.
  • Saturated fine -grain roadbed soil could experience modulus reductions of over 50percent.

Most of the water in a pavement section infiltrates through the pavement surface during rainevents. The incorporation of open-graded, free draining base/sub base layers into the pavementsection as shown provides excellent drainage. For this the requirement of good quality graded aggregate is a must, whereas the project site conditions contradicts the requirements. The available aggregate were of marginal quality which needed to be stabilized to achieve desired modulus values. In the process of stabilization, it was of utmost importance to ensure proper drainage requirements. 

Solution Proposed

After a careful evaluation of the project requirements and site conditions, Central Road Research Institute (CRRI) has carried out detailed analysis and approved the usage of Techdrain Drainage Composite TDC 55130 which is in accordance with the requirements of MoRTH specifications section 704.  The pavement designs submitted to CRRI were reviewed using IIT Pave software and permissible strains were computed using IRC 37:2012 and the layer thicknesses were recommended as tabulated below:

S. No

Type of Layer

Layer Thickness

1.

Bituminous Concrete with VG 30 Bitumen

40 mm

2.

Dense Bituminous Macadam with VG 30 Bitumen

60 mm

3.

Paving Fabric – SAMI Layer

As per MoRTH Section 708

4.

Stabilized Base Course

175 mm

5.

Geocomposite Drainage Layer

As per MoRTH Section 704

6.

Stabilized Subbase Course

150 mm

7.

Prepared Subgrade

500mm

 

As per IRC 37 Clause 7.2.2, it is required that the stabilized soil layer should retain the permeability when water is likely to enter into pavement from shoulder, median or through cracks. It was therefore recommended that Techdrain Drainage Composite which possess required permeability and facilitates the subsurface drainage shall be laid between base and sub base layers. It was ensured that the drainage composite layer is running upto the end of the toe for sub base layer including shoulders. Following is the typical cross section of the pavement structure adopted for construction.

Execution On Site

Storing and Handling:

  • Never drag the Drainage Composite Rolls, it may lead to damages.
  • The recommended method of unloading is, to use the Stout Bar. A Bar can be passed through the roll tube & attached via chain, which in turn can be lifted by Hydra Crane or Forklift. The sequence for the same is shown in figure below.
  • The forks of a fork lift should never be used, under any circumstances, to unload rolls, this would incur heavy damage to the roll.
  • The Drainage Composite shall be kept dry and wrapped such that it is protected from any damage during shipping and storage. If stored outdoors, it shall be elevated and protected with a cover.
  • The Rolls should also be carefully handled when being deployed from storage to their position just prior to installation.

CONCLUSIONS

Techfab India has supplied the entire quantity of TechDrain Drainage Composite within the stipulated time and meeting all the quality requirements. The road construction has been completed by KMC Constructions Ltd. and is open to traffic. The project met the desired objectives and road is functioning well.

Related Products

TechDrain - Drainage Composite