OUTLINE:5-15 – GEOPLASTIC FABRICS

6-01 - DRAINAGE 6-02 - HYDROLOGY 6-03 - DRAINAGE ECONOMICAL

CONSIDERATIONLALLO, KILVEN Varde

GEOPLASTIC FABRICS

5-15

Geoplastic Fabrics

• The Geoplastic Fabrics were introduced and experimented in Europe in the year 1970.

• They were used to reinforce soil of pavement and to provide drainage and erosion control for highways and railroads.

The Functions of Geoplastic Fabrics:

• as FILTER• as DRAINAGE• as SEPARATOR• as REINFORCEMENT• as ARMOR

Materials

• Polypropylene• Polyester• Nylon• Polyethylene• Polyvinyl chloride

Difference in Properties includes:

• Specific gravity• strength• Future stain• Modulus of elasticity• Creep resistance• Resistance to ultra-violet light and biological

effects

Construction Methods

• Woven Fabrics

• Knitted Geoplastic Fabrics

• Non-woven or Non-knitted Fabrics

Woven Fabrics

The filaments are directed in two perpendicular directions and overlapped.

• The Monofilament Fabrics are woven form single strand.

• The Multifilament Fabrics are made from yarns with many fine strands.

• The Ribbon Filament Fabrics are made from strands with widths several times their thickness.

Woven

Knitted Geoplastic Fabrics

• Is made of loops of fibers connected by straight segments. They could be stretched in either direction without significant stresses to the fabrics.

• Knitted Geoplastic Fabrics in tubes serve well as filters around drain tile particularly for agricultural needs.

Knitted

Non-woven or Non-knitted Fabrics

• The fibers or strand arrangement are held together under the following manner:

1. Needle punching through the fabrics2. Heat bonding or melt bonding3. Resin bonding wherein the fabric is impregnated with

a resin which cements the fibers together.4. Combination bonding is the combination of two or

more of the processes described to produce a particular characteristics.

Non woven

VIDEO for Geoplastic

DRAINAGE6-1

Drainage

• Is defined as the means of collecting, transporting and disposing of surface water originating in or near the right of way, of flowing in stream crossing or bordering the right of way.

• About 25% of roadway funds are spent for culverts, bridges and other drainage structures. And any other structures involving drainage

• Surface drainage is only one among the many problems to be considered in establishing the location and construction of roads

• The most favorable location of a roadway is the division between large drainage areas. All streams must flow away from the right of way to reduce the drainage problem.

Surface drainage problems follow these basic considerations:

•Hydraulic Design

•Erosion Control

HYDROLGY6-2

Hydrology

• Is the branch of physical geography that deals with water of the earth.

The branch of Hydrology that concern Highway Engineers are:

1. The frequency and intensity of precipitation2. The frequency that this precipitation brings the

highest run-off which are equal or exceeded critical values.

3. The distribution of precipitation throughout the seasons that influences water behavior affecting the highway surfaces.

4. The prediction regarding future rainfalls or run-off from gathered statistical approaches, formula, or simulated methods based on the laws of probability.

Run-off is Predicted based on the following methods.

1. Rational Methods2. Empirical Formula3. Unit Hydrograph4. Statistical Approach5. Simulation

Relationship and effect of Hydraulic and Construction

• Highway construction disrupt existing natural drainage pattern.

• Construction operations may disturb the ground cover and loosen the soil creating muddy stream as a result of erosion.

• Every drainage installations disturbed the ecological balance of nature.

• Any changes in the land use may alter the historical run-off or un-gauged rural water shed that could be disastrous on wide scale basis.

Cardinal rules

• As much as possible, any existing drainage system patterns and soil cover should not be disturbed.

• Necessary changes in the drainage patterns should not in any manner bring velocities that may create new erosion problems.

DRAINAGE ECONOMIC CONSIDERATION

6-3

• The term economy in drainage system, means: finding the solution to a problem that is cheapest in the run under the following condition:

1. Determine the estimated initial investment cost.2. Consider the maintenance cost or outlay.3. Consider anticipated loss and damage for each

solution

• Under the foregoing considerations, annual appropriation for possible drainage or economic loss is equal to the estimated losses from floods of various magnitudes, multiplied by the probability that these floods will occur any time of the year.

• For instance, if the drainage loss from any flood exceeding the design flow is P200,000 and according to hydraulic computation such floods will occur once in every 5 years, then the annual loss of flood damage is P200,000 divided by 5 years or P40,000 per year.

• For major highways, projections might proved that drainage facilities should accommodate a 50 year flood, whereas, the design based on a 5 years is reasonable for a low volume rural roads.

• Drainage problem is varied, and there is no single set of assumption or rule to economic problem in drainage, considering the uncertainty of flood frequency where the design is based. To major highways with large volume of traffic, losses to motorists and to the economy, is tremendously high, if the road will be closed frequently, due to flood and washout.

• Economic studies based on reasonable estimated costs and possible damages, represents the best approach, flood frequency and some of the cost, must be thoroughly approximated and let catastrophic occurrences pervert our perspective of cost risks.