Saturday, December 4, 2010

An executive method for embankment layers in roads and yards


    Abstract:
This is a technical note of “An executive method for embankment layers in roads and yards”.
When we proceed to execute a compacted layer, for example: soil, Base, Sub base layer in road and yards, we should know how much the soil or aggregate (as a base or sub base layer) per square meter is need for reaching to specifications of design (thickness, percentage of compaction).
Author has presented an executive method to solve of above problem in this technical note.
    Introduction:
After designing of a pavement for roads or yards, civil engineer obtains several layers of aggregates (base or sub base) and soil that they must be compacted and executed under asphalt. Each one of these layers has its own specifications included: thickness, percentage of compaction, maximum dry density, optimum moisture, atterburg limits, sandy equalent, crashing percentage and etc.
Two specifications of them are very important: thickness and     compaction percentage. In this manuscript it has been calculated: “what is the distance between unloading of two consecutive Damp Trucks a long road so that two important specifications are produced?”
     Main body Of Article describing work and results:
     The following is a list of symbols used throughout the text:
-      w%    Natural moisture of the soil
-      Dn      Natural unit weight (Free unit weight of the soil)
-      Dm     Maximum dry density
-      R %   Compaction Percentage (Design Specification)
-      Z        Thickness of layer (Design specification)
-      V2       Volume of dry compacted soil after filling
-      m2      Weight of dry compacted soil after filling
-      m1      Weight of natural soil (Free)
     - A          required Area (XY) for unloading soil of each Damp Truck
     - V1         required Volume of unloading soil on Area (XY) by each Damp Truck
In order to execute a filling layer on sub grade in the road, we start it in accordance with four stages as follows:
A)  Unloading of soil or aggregate on required area (XY) of sub grade with required volume (V1) by a Damp Truck.
B)  To distribute storage area of soil (Unloaded by Damp Truck) by a Grader so that the soil or aggregate layer reaches to thickness of design specifications.
C)  Spraying on soil by watering - Can Truck in order to reach the soil or aggregate to optimum moisture.
D)  To compact the soil or aggregate by a Roller in order to reach to compaction percentage of design specifications.
    In this technical note, the target is to obtain the required area (XY) for unloading soil of each Damp Truck or the required volume (V1) of unloading soil on area (XY) by each Damp Truck for reaching to specifications of design.

    In order to solve above problem, author has used from returning    analyze as follows:
   An element of soil (X, Y, Z) has been considered after executing of the last stage (stage D).

  Where:
V2 = Z.X.Y                                                             (1)
m2 = Dm. Z.X.Y.R                                                      (2)
m1 = m2 + (m2 * w %) = m2 (1 + w %)                       (3)
Therefore, it could be used from below formula:
V1 = m1 / Dn = Dm.Z.X.Y.R((1 + w %) / Dn                 (4)
X.Y = A = V1. Dn / Dm.Z.R((1 + w %)                        (5)
Example (1):
w = 3 %
Dm = 2.17 gr / cm3
R = 95 %
Dn = 1.53 gr / cm3
A = 10000 cm2
Z=15Cm
V1 = 2.17 * 15 * 10000 * 95 % * (1 + 3 %) / 1.53
V1 = 0.2 m3
Example (2):
w = 3 %
Dm = 2.17 gr / cm3
R = 95 %
Dn = 1.53 gr / cm3
V1 = 6 m3 = 6000,000 cm3
Z=15Cm
6000,000 = 2.17 * 15 * 95 % * (1 + 3 %) A / 1.53
A = X.Y= 288226 cm2
A # 29 m2
Conclusions:
In this technical note, author has tried to show what is the distance between two consecutive soil storage area that they have been   unloaded by Damp Trucks for reaching to design specifications in roads and yards.
It is possible only with having results of laboratory tests.
Easily, we can see that above problem is independent of optimum moisture.