Islamic University of Gaza Civil Engineering Department Surveying II ECIV 2332 By Belal Almassri

Chapter 9 Route Surveying – Part 1 - Definitions. - Horizontal and Vertical alignment. - Types of Horizontal Curves. - Simple Circular curve geometry. - Terminology and Formulas.

Route Surveying - Route Surveying is the branch of surveying that performs the survey works (mapping and setting out) of routes (highways, railways..etc). - Route surveying is comprised of all survey operations required for design and construction of engineering works such as highways, pipelines, canals, or railroads. - Design of Routes includes: 1. Horizontal Alignment. 2. Vertical Alignment.

- Horizontal Alignment: consists of straight lines (tangents) and horizontal curves. - Vertical Alignment: consists of straight lines (gradients) and vertical curves. Types of Horizontal Curves: - A. Circular Curves: 1. Simple Circular 2. Compound Circular. 3. Reverse Circular. 4. Spiral Circular. 5. Broken Back Circular.

Broken Back

Notes on the Circular Curves: The broken back type is being used inside the town on the other hand the reversed type is being used outside the town In the broken back type, if the distance between A and B is greater than 30 meters then each one of them is called simple For safety reasons the reversed type should be avoided as possible.

B. Transitional Curves: - - A mathematically calculated curve on a section of highway, or railroad track, where a straight section changes into a curve. It is designed to prevent sudden changes in centripetal force. - - F = mv ²/r F: centripetal force. m, v: mass and velocity. r: radius. It start with radius equals infinity (straight line) so the F value will be zero and then the r is going smaller and smaller.

Simple Horizontal Circular Curve Geometry

R, RADIUS: The radius of the circle where the radius is always perpendicular to back and forward tangents. PC, POINT OF CURVATURE: The point of curvature is the point on the back tangent where the circular curve begins. PT,POINT OF TANGENCY: is the point on the forward tangent where the curve ends.

PI, POINT OF INTERSECTION: The intersection of the back and forward tangents. L, LENGTH OF CURVE: The length of curve is the distance from the PC to the PT, measured along the curve. T, TANGENT DISTANCE: The tangent distance is the distance along the tangents from the PI to the PC or the PT. E, EXTERNAL DISTANCE: The distance between the PI to the mid of the curve.

LC,LONG CHORD: The long chord is the straight-line distance from the PC to the PT. Δ, CENTRAL ANGLE: The angle between two radii of circle. M, MIDDLE COORDINATE: The distance from the midpoint of the curve to the midpoint of the long chord.

- All of the formulas in terms of R and Δ, where R is known and Δ can be measured from the field.

Quiz