Design of Storm Water Drainage System to Enhance Ground water Level-A Case Study on Hosur Inner Ring Road (IRR)

Drainage of water from pavements has been an important consideration in road construction for more than 2000 years. However, modern processing, handling, and placement of materials frequently result in base courses that do not transmit water or drain; combined with increased traffic volumes and loads, this often leads to pavement distress caused by moisture in the structures. Water related damages on the pavement can cause one or more of the following forms of deterioration, (i) Reduction of sub-grade/sub-base strength (ii) Differential swelling in expansive sub-grade soils (iii) Stripping of asphalt in flexible pavement, etc., Free water is the form of most concern to the designer because it can decrease the strength of the pavement and is the only form of water that can be significantly removed by gravity drainage (Lytton et al., 1993). The present study is to investigate on storm water drainage system on Hosur-Inner Ring road and to Design the sub-surface drainage system. Study area was considered on Hosur-Inner ring road between ESI hospital and Anand Electronics (km 0/0 ? km 8/850).The selected stretch for our study was paved stretch 1 km (km 6/100 to 7/100) and unpaved stretch 1 km (km 7/155 to 8/155). Geometrical characteristics of the road were analyzed about longitudinal and transverse profiles on both stretches and design of drainage system was done for unpaved stretch. The investigations were carried out by field surveys to obtain the sag points longitudinally and along the cross sections to determine their geometric properties. The primary source of water in pavements is atmospheric precipitation. This water can enter the pavement through several ways (e.g., cracks, infiltration, through shoulders and ditches, high groundwater) and is moved by an energy gradient, such as gravity, capillary forces, osmotic forces, and temperature or pressure differences. The drainage system is primarily concerned with saturated gravity flow, which can be determined by application of Darcys law. To understand and analyze the conditions under which the pavement must function, The information needs on highway geometrics, surface drainage, non-pavement subsurface drainage, climate, and soil properties. The details such as, Traffic data, Road Cross sectional details and Rainfall data for last 10-year, were collected from Highways Department and Taluk office, Hosur respectively and the laboratory tests on sub-grade material was conducted on three soil samples collected at every 300 m interval at a depth of 1 m below the earth surface. Laboratory investigations included determination of Gradation, Natural Moisture Content (NMC),Optimum Moisture Content (OMC), Maximum Dry Density (MDD), and Permeability (K). From the above soil tests it was observed that, the soil type is well-graded soil. The nature of soil is semi-pervious and the drainage property of the soil is Excellent. Based on the geometrics of road and natural properties of soil, the sub-surface drainage system was designed for selected stretch considering Hydraulic and Hydrological parameters. Several combinations of criteria and equations were selected to calculate the required permeability of the drainage layer. The criterion selected has much more influence than the equation used; therefore, the drainage criterion should be selected and calculated with the aid of Nomographs, Family and Group curves. These data enable the designer to predict the amount of free water that will enter the pavement structure, to predict the free water surface. The free water can be removed by draining vertically through the subgrade or laterally through a drainage layer.