27-06-09
To determine the modulus
To determine the modulus of elasticity and to control the quality of the sections performed, a FWD machine was used. The structural condition of a multi-layered traffic lane during utilization can be determined by the deflections (deformations) caused by heavy traffic. With these known deflections under a controlled load and with the assumption of a suitable model, it is possible to back-calculate the material-constants and the stress and strains in a multi-layered pavement structure. They are basis for further design calculations.
The applied dynamic impulse load will cause the biggest deflection at the center of load and corresponding lower deflection values at distances away from the center of load. Connecting these single deflection values graphically a so-called deflection basin is determined. If the resulting stresses and strains resulting from a controlled load in a single structural layer are compared with the allowable material constants for materials used in connection with allowable load-repetitions, the structural condition of a multi-layer pavement can be evaluated and the service live can be estimated.
To enable the back-calculation of the elastic modulus of the single (individual) layers of a pavement, the thickness of this layer must be known (e.g., determined by geo-radar or by means of extracting cores drilled) as well as the deflection-basin.
08:38 Gepost door Nimerteras in Algemeen | Permalink | Commentaren (0) | Email dit | Tags: to determine the modulus |
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Working process-included
Working process-included delivery of the gravel-sand mixture, distribution of the material by graders and pre-compaction with single drum rollers to [greater than or equal to]95% proctor density (to produce a stable sub-layer for stabilization). A spreader mounted on a three axle's truck applies cement to the surface, which had previously been wetted because of the strong wind in the project area. The spreader had a capacity of 10 tones with cement spreading electrical control, which was able to spread cement precisely and independent of truck velocity. The spreader's auger and chain voids enabled the cement to spread with exact width of 2.5 m. For application of roads shoulders and intermediate strips, the spreading width decreases to 0.80-1.70 m.
The cement was mixed into the soil by stabilizer with a working speed of 6 m min and a cutting depth of 250 mm and simultaneously dosing and applying bitumen emulsion and water into the layer across 8 m width of the road. A 19 tons roller takes care of the pre-compaction of the stabilized layer, which is leveled by a grader and finally is compacted by the second 19 tons roller.
To guarantee the predicted compaction of stabilized soil using cement and bitumen emulsion, 19 tons rollers were equipped with vario-control system and the results were subsequently printed out in the machine. Vario-control system is mounted inside the drum and at any position; the maximum compaction energy applies automatically. This system analyses the stiffness between the material and the drum. The requirement vibration at any angle between vertical and horizontal with amplitudes of 2.5 mm and centrifugal force equivalent to 500 kN will produce.
08:36 Gepost door Nimerteras in Algemeen | Permalink | Commentaren (0) | Email dit | Tags: working process-included |
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The stabilizers fitted with water
The stabilizers fitted with water and bitumen emulsion and dosing equipment. The miller, working weight 20 tons, engine power 300 kW, working width 2.50 m and maximum working depth 400 mm, has a combined buckle and back axle steering, all-wheel drive, hydrostatic operating, rotor drive and automatic performance control. The rotor has 210 milling chisels and rotates opposite to the working direction. The number of rotations can be set in 11 levels between 100 and 170 rotations [min.sup.-1] and/or set according to the requirements of the construction. The construction of the rotor cover with a variable rear hatch allows thorough mixing of the ground, binder and water components and even surfacing of the stabilized layer. The bitumen emulsion equipment with the bitumen pump, spraying beam and special nozzles for the spread of the bitumen emulsion has an easy to use manual dosing system for the control of the spray content. The nozzles can be dually controlled so that for overlapping and construction on the shoulders, the working width can be varied. A separate water-spraying beam with speed independent dosing system enables optimal moisture content for the base course material. A bitumen emulsion tank wagon, 10000 L, in front of the ground stabilizer and a water tank wagon, 7000 L, behind it supply the stabilizer with binder and water.
For the main compaction of the stabilized layer two 19 tons roller trains used, which guaranteed secure and thorough compaction of the bitumen emulsion-cement-ground mixture. The roller trains were equipped with the measuring system for controlling the compaction level, which carried out a measurement approximately every 40 mm.
08:35 Gepost door Nimerteras in Algemeen | Permalink | Commentaren (0) | Email dit | Tags: the stabilizers fitted with water |
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