3 Soil Compaction And Stabilization

3 Soil Compaction and Stabilization Recommended reading: Chapter 2, S.W. Nunnaly - Construction Methods And Management, 2006.

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Example:

Example

Soil compaction and stabilization

Compaction can be done by the following four basic forces: 1. 2. 3. 4.

Kneading Action Impact Vibration Static Weight

Types of Compacting Equipment: Equipment manufacturers have developed a variety of compactors that incorporate at least one of the compaction methods and in some cases more than one, into their performance capabilities. There are many types of compaction equipment such as: 1

– Tamping Rollers a- Sheepsfoot rollers: • These rollers are either self-propelled or towed drums. • These rollers have steel wheels equipped with cylindrical pads or feet. • It utilizes static weight and kneading to achieve compaction. • Suitable for compacting all fined-grained materials, but is generally not suitable for use on cohesionless granular materials.

b- Modified Tamping rollers: • Self-propelled nonvibratory rollers • The pads are tapered with an oval or rectangular face • The pad face is smaller than the base of the pad at the drum • Effective on all soils except pure sand. 2 – Smooth wheel Rollers: These rollers can be classified according to its type or weight. A - By type:

• Three wheel & two axle rollers • Two wheel tandem rollers • Three wheel tandem rollers. - The three wheel & two axle rollers are used for granular & granular plastic material. - The two & three wheel tandem used for sandy soil granular material with clay binder. B- By weight: For example 10 ton, 20 ton ……etc. The compacting drums are empty and can be filled with sand or water to. When it says that a smooth wheel roller with (14 – 20) ton, that means the weight of the smooth wheel roller is 14 tons and can be increased to 2o tons. 3- Pneumatic - tired rollers: These are rubber tire rollers filled with air. Types: i)- small types → used for sandy silt , sandy clay , gravely sand. (4-9) tires on one axle. ii) - Large type → used for all types of soil & all depths. With (15-20) ton. There are types called Pneumatic rubber roller with variable air pressing which enables the operator to change the pressure of the tires without stopping.

Types of vibratory compacters : 1 – Sheepsfoot vibratory compactors

2 – Steel drum vibratory compactors. 3 – Pad type vibratory compactors. 4 – Manually operated vibrating compactors -

Used in confined areas where large compactors could not operate Can be operated either manually as a walk behind unit or by remote control.

Walk-behind vibratory plate compactors

Small vibratory rammers

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Example:

Soil Stabilization

The reason of compaction is for improving soil properties to: 1 – Reduce or prevent settlement. 2 – Increase strength. 3 – Improve bearing capacity. 4 – Control volume changes. 5 – Lowering permeability.

Example:For the compaction of a road of 8 km length & 10 m width use clay soil with the thickness of the layer is 0.2m use a smooth wheel roller. Determine: 1 – The time required for compacting the road. 2 – Number of trucks for providing the required soil for filling of the roads. If: 1 – Width of roller = 2.1m. 2 – Number of compactions = 9 times. 3 – Percent of stopping = 20%. 4 – Capacity of trucks = 15m3 (loose material) 5 – Over lap of layers = 10 cm. 6 – Velocity of roller = 4 km/hr. 7 – Hour of working = 50 min. 8 – Day of working = 8 hr. 9 – Density of soil = 1450 kg/m3 (loose material) Density of soil = 1800 kg/m3 (compacted material) Solution: 10 No. of road parts = = 5 part or five times the roller will move on the road. (2.1 − 0.1) Total compacted length (D) = 5 * 8 * 9 = 360 km ‫الطول الكلي المحدول لكل شريحة‬ D 360 Work time (hr) = = = 108 hr. of work. ‫ساعات العمل الفعلى للحادلة‬ 50 V 4* 60 108 Work time (day) = = 13.5 ≈ 14 days. ) ‫الزمن الفعلي بدون توقف ( ايام‬ 8 14 Duration (with stopping) = ≈17.5= 18 days. ‫الزمن الحقيقي مع التوقفات‬ 1 − 0.2 Volume of compacted material(c.m) = (8*103*10*0.2) = 8000*10*0.2 = 16000 m3 1800 ) = 19862 m3  Volume of loose material ( l.m) = ( 16000* 1450 19865 No. of trucks = = 1325 15

Tutorial: A section of highway needs to be supplied with base course for the subbase layer. If the thickness of layer is (0.25m), the width of the road is (7.2m) and the length is (3 km). Assume that the swelling is 25% and the shrinkage is 10%. Find:

1. The number of trucks to supply material, if the capacity of each truck is 12.5 LCM, and each truck will supply material for 40 times. 2.

The distance between two successive unloading points.