UNIVERSITY OF AVEIRO Department of Civil Engineering

PROJECT OF THE ROAD DRAINAGE

Authors:

Katarzyna Świstek 71510
Anna Kur 71440
Magdalena Dopierała xxxxx
Marta Moskalik xxxxx

2013/14

Table of content:

1 - General Considerations

2 - Hydrology

2.1 - Precipitation

2.2 - Duration of rainfall

2.3 - Flow calculation

3 - Transverse Drainage

3.1 - General

3.2 - Hydraulic Design of aqueducts. Methodology

3.3 - Construction of transverse drainage

3.4 - Implementation of works

4 - Longitudinal Drainage

4.1 - Platform Surface drainage

4.2 - Surface drainage of excavation and embankment slopes

4.3 - Drains and collectors

4.4 - Hydraulic Design

5 - Internal Drainage

1 – General Considerations

The basic objective of road drainage design is the reduction or (if possible) elimination of the energy generated by flowing water. The destructive power of flowing water increases when its velocity increases. Therefore, water must be forbidden to achieve volume or velocity sufficient to cause excessive wear along ditches/gutters.

The presence of excess water or moisture within the roadway can worsen the engineering properties of the materials used in construction. Badly designed drainage can cause road surface erosion, weakening subgrades and, in extreme cases, failures of the construction.

It is essential that adequate provision is made for road drainage to ensure that a road pavement performs satisfactorily. The main functions of a road drainage system are:

• To prevent flooding of the road and ponding on the road surface
• To protect the bearing capacity of the pavement and the subgrade material
• To avoid the erosion of side slopes

As a general conditions affecting our project we specified three main factors affecting location, design and construction of the road: the topography and the morphology of the terrain, the amount and intensity of rainfall and the construction types of sewers and gutters.

1. The topography and the morphology of the terrain – Because of the diverse lanform in the area of the road construction it is necessary to devide the area for the proper drainage section, for which a different coefficients will be used. The section are as following – pavement, slopes and adjacent areas. Terain morphology impacts road drainage and road stability. Important factors are slope shape, slope gradient, slope length, stream drainage characteristics and others.

2. The amount and intensity of rainfall – Hydrologic factors are important in locating roads. They and the topography force the aplication of slopes. Water collected from upper positions on the slope will concentrate in the lower positions. The area of our project is an area where the average peak of rainfall is 67,49mm/h. The drainage system should be designed in such way to provide times of capture all the water during those peaks. Sizing of all gutters and corresponding drainage structures is a result of this hydrological data.

3. The construction types of sewers and gutters

2 – Hydrology

2.1 - Precipitation

We have to take into account different aspects of precipitation:

Total rainfall: Amount of fallen precipitation per unit of area during time interval [l/m²]

Useful precipitation: part of the total rainfall that infiltrates into the surface or flows directly to the sewage.

Flow basis: part of the total precipitation infiltrating having a certain retention time in the soil, causing the sub-surface drainage and groundwater flow returning to the surface within the confines of the basin.

Precipitation lost by evaporation, transpiration, soil storage and deep percolation - this part does not participate in the transformation rainfall-runoff scheme.

2.2 - Duration of rainfall

For determinating the average rainfall in the area where our work we have used the data from Portuguese Institute of Sea and Atmosphere. The data obtained from the institute are the average annual rainfall in mm/year and from the last 65 years. The result obtained by this scale has been 380mm/year.

2.3 - Flow Calculation

For the calculation the volume of flow in gutters we use the expression:

$$Q\ = \frac{\text{CxIxA}}{3.6}$$

Where:

c – Runoff coefficient;

• Pavement C = 0.95

• Slope C = 0.7

• Adjacent areas C = 0.5

I – Intensity of rain per hour [mm/h];

A – Area from witch a gutter collect water [km²].

3 – Transverse drainage

3.1 - General

The need of building an aqueduct results from the presence of a zone of very large extension where water would flood the route. This aqueduct is perpendicular to the road and its dimensions (diameter, length, inclination) are calculated by the methods defined in section 3.2.

Also highlights the presence of manifolds which may be interconnected below the platform through transverse drains in order to evacuate the water laterally may be addressed to the foundation of the platform and as the regulations in the field of engineering civil.

3.2 - Hydraulic dimensioning of aqueducts. Methodology

Steps to follow for dimensioning the aqueduct:

1. Determination of the area from which the water will flows to the aqueduct by studying the slopes, adjacent areas and other.

2. Calculate peak discharge of water to be poured over the aqueduct through the following formulation:

$$Q_{p} = \frac{\text{CIA}}{360}$$

$Q_{p}\ \lbrack\frac{m^{3}}{s}\rbrack$ $\text{I\ }\left\lbrack \frac{\text{mm}}{h} \right\rbrack$ A [ha] C [−]

1. By establishing peak flow and the speed limit for the flowing water 3m³/s to determine the diameter of the aqueduct.

3.3 - Construction of transverse drainage

Transverse – underground drains: are placed under the pavement to collect and drain water laterally to flow along the pavement foundation.

Aqueduct: It’s dimensions are shown in the chapter with calculations

4.4 - Implantation of works

In the method of construction of the aqueduct we have to consider 3 main parameters: level of water at the entrance, at the exit and critical level.

Control of the water level at the entrance

Control of the water level at the exit

Thern it is necessary to define Ke – loss of load on the entrance value.

Next step is to define critical level of woter in the aqueduct

There are given parameters for the realization of the aqueduct:

Data obtained:

Diameter (normalized) = 0.8m;
Hw speed (entrance) = 1.04m;
Hw (exit) = 0.708m;
Flow Rate = 6m³/s

4 - Longitudinal drainage

4.1 - Surface drainage Platform

Platform Ditches along the pavement are coated so its minimum slope is 2%. Their shape is triangular.

As for the flow watering the ditches platform we used the specific formulation for these cases, which relates the surface area of the falling water, the amount of rainfall and a coefficient as asphalt, fill or excavation and free ground. Being asphalt coefficient C = 0.95

Q=(A x I x C)/3.6

4.2 - Surface drainage of excavation and embankment slopes

For drainage of the slopes we used two different types of gutter depending on where the water comes collecting.

Crest ditches : Responsible for collecting water from adjacent land of excavation slopes. For uncoated concrete low slope is 2% while for the coated will be 0.5%. Both can be made triangular or half-round, in our case a half-round.

Valeta de banqueta em meia cana- Ditch of stool in half cane

Pormenor tipo de banqueta c/ valeta triangular- Detail type of stool c / ditch-triangular

• Ditch the bench: Serve to collect the water coming from an upper plane of the slope thus avoiding that they can create instabilities in the same structural type. In the case of the minimum pitch uncoated will be 4% and 0.5% for the coated if (our case). Also they can make half-round or triangular as in our case.

Pormenor tipo de valeta de crista em meia cana- Detail type of trench crest in cove

Pormenor tipo de valeta de crista triangular- Detail type of ditch ridge triangular

2. When embankment:

In case the batter is from aterro we have used the following types according to the situation ditchs:

• Ditch foot embankment: Responsible for collecting water from the slopes of terrified, thus protecting this land adjacent. Its geometry is triangular cross and minimum slope is 1% for the coated (our case) and 2% for uncoated.

Pormenor tipo de pe de talude em betao- Detail type of foot embankment, concrete

Ditch surround the landfill: Also called ditch berm serves to collect water from the road, avoiding the discharge of the same forThe fill slope, which could cause instability. As to their geometric characteristics stand is half round, covered with concrete and with a minimum slope of 0.5%.

Valeta de bordadura de aterro- gutter surround landfill

Pormenor tipo de bordadura de aterro - Detail type of surround landfill

4.2.1 Elements of extra drainage used

-The emergence of various factors such as excess flow in gutters has necessitated the construction of other elements for proper drainage of your stretch in which we are working.

• Box of water link: Used to link two or more gutters. In our case we have used to connect with crystal gutters slope in points of this union has become necessary, these indicated in the relevant drawings.

caixa de ligacao de Aguas- connecting waters box

Serve para ligar 2 ou mais valetas, normalmente ligando as valetas de crista/banqueta a descida de talude. - Used to connect 2 or more trenches, usually linking the ditches crest / footstool's descent slope.

Esquema tipo de uma Caixa de ligacao - Schema type of a connection box

Run Slope: Used to join gutters crystal and slope with gutters sidewalk and platform, have taken advantage of link plascaixas making them coincide with the you descindas, thereby lowering the waters of different gutters to sidewalk.

Descidas de talude- Downhill slope

Servem para guiar as aguas vindas da valeta de crista/banquta ate a valeta de banqueta/platform- Serve to guide the welcoming waters of the ditch Crest / sidewalk until the ditch of footstool / platform

• Collectors: Excessive flow in certain areas has become inevitable construction of collectors, which will discuss in depth in the next section of the schedule.

4.3 Containers and Drains

Excessive flow that have come to achieve some of the gutters and the flow velocity of the water that runs through the relaxation of the load carried by them has necessitated by discharging water on the sidewalk or platform ditch. So we've carried out the construction of a drainage network based on the interconnection of different gutters through through Connection Boxes and declines slope. All waters are discharged after ditch lower bound, which is the platform. However this has not ditch ability to absorb the flows that derive from it so that the construction of a very important and basic drainage on this stretch of the route element, collectors have been necessary.

The operation our drainage system is simple, at strategic points indicated on the drawings have different gutters interconnected through of Connection Boxes between gutters to same level and with gutters slope diverted of a different dimension. The final section of this water circuit is in ditch platform where we take to run a sump with a small deposit that a party or by passing the collector, as that section of it we are.

We used the presence of a closed deep for the discharge of water from the collectors, thus avoiding the construction of new drainage elements and saving a significant amount of money. So pouring water drained this gated has been the most simple, economical and safe solution for anything or not affect the stability of the ground or the course of the work.

The geometric characteristics of the collectors are:

-Cross-Geometry: Circular with 2% minimum slope

-Materials: PVC (for the nature of the work was not necessary to use concrete thus an important save money)

Pormenor tipo de coletor- Detail type of collector

Sumidouros/ sarjetas – E um dispositibo de recolha da aguas das valeta que as encaminha ate ao coletor. A entrada da agua e feita atraves de uma grelha superior (sumidouro) ou de um rasgo lateral (sarjeta) - Drains / gutters - and a device for collecting the waters of the ditch that routes up to the collector. The entry of water and taken through an upper grill (sink) or a lateral tear (gutter)

4.4 Hydraulic Dimensioning

As for sizing hydraulic calculation method is simple and relates well to all areas of our section, but the only difference is the method used to collect the water, through gutters, collectors sinks or aqueduct.

• Method of calculation

Distinguish the main parts:

1. Point calculation flow rate based on three main factors, area over A falling precipitation, amount of rainfall and surface type I on falling precipitation C. All these factors are related to the following expression that defines the peak flow:

Caudais afluentes- tributaries flow

Caudal a escoar determinado pelo Metodo Racional- Flow to flow determined by the Rational Method

Intensidade de precipitacao (I) calculada pelas curvas IDF: - Precipitation intensity (E) curves calculated by the IDF:
- period de retorno (T) de 10 anos. - Return period (T) of 10 years.

• Duracao da chuvada (t) de 10 minutos - Drench length (t) 10 minutes

Coeficiente de Escoamento ( C) -Runoff Coefficient (C)

Local- sectional

Faixas de rodagem e bermas revestidas- Lanes and curbs-coated

Taludes se escavacao (ou Aterro) com revestimento vegetal- Excavation slopes (or landfill) with coating plant

Terrenos exteriors a Estrada- Exteriors land the road

1. Sizing and manifolds gutters determining a maximum flow rate and maximum diameter of 600mm also.

Valetas e Coletores- Dimensionamento- Ditches and Collectors-Sizing-

Qe por meias canas- by canes stockings

Qe por Manilhas de Betao - Shackles for Concrete

Valeta reduzida em Betao- Reduced in ditch Concrete-

Valeta de enrocamento argamassado- Ditch rockfill argamassado(?)

internal drainage

Due to the large amount of data and expressions and in order that the understanding, expression and clarity of all calculations (areas of the basins, flow rates, diameters gutters collectors, etc.) are the best possible, we performed the following Excel document where all calculation expressions and results obtained for the stretch of road that takes us to get detailed.