Earthworks 3

Understanding Embankments and Groundwater Control

Definition and Function of Embankments

• An embankment is defined as an artificial bank raised above the surrounding land to redirect or prevent flooding from rivers, lakes, or seas.

• The design profile of an embankment depends on various factors including its purpose, proposed loads, type of fill material, and ground stability.

Construction Considerations

• The stability of the ground where the embankment will be constructed is crucial; existing conditions must be assessed before construction begins.

• The strength properties of the fill material can be affected by construction methods and adverse weather conditions, particularly when using clay and fine sand.

Embankment Design Parameters

• Safe angles for embankment slopes vary based on fill material; they can range from 45 degrees for rock fill to as low as 20 degrees for some clays.

• Slope ratios may also be expressed in percentage terms (e.g., a slope ratio of 1:3 corresponds to approximately 33 degrees).

Groundwater Control Techniques

Permanent Exclusion Methods

• Permanent groundwater control involves creating impervious walls underground to prevent water ingress; these walls often require interlocking joints lined with waterproof materials.

• Freezing methods are mentioned but not commonly used in Malaysia; instead, chemical solutions like magnesium and calcium chloride are utilized at specific temperatures to create ice barriers against water flow.

Temporary Exclusion Methods

• Commission pumping is highlighted as a widely used method for lowering groundwater levels economically across various soil types; it typically maintains depths up to 1.5 meters.

• Pumping from wells involves lowering groundwater levels significantly (up to nine meters) using larger diameter wells equipped with submersible pumps for deeper excavations.

Advanced Groundwater Management Techniques

Electro-Osmosis Method

• Electro-osmosis is described as an expensive technique suitable for cohesive soils that uses electrical currents to manipulate water movement away from excavation areas by charging water molecules positively and negatively. This process disturbs natural balances within the soil structure.

Excavation and Compaction Techniques in Civil Engineering

Understanding Electrode Functionality in Soil Treatment

• The positive electrode can be represented by sheet piling, while the negative electrode is identified as the well point. A direct current (DC) is supplied through clay soil to facilitate the migration of pore water towards the negative electrode (cathode).

• When current flows through the ground, positively charged water molecules move toward the negative point, which is pumped out. This method requires a significant amount of power.

Importance of Soil Compaction in Construction

• In civil engineering and construction practices, whether soil is imported, excavated, or reapplied, compaction plays a crucial role. It is essential for structures such as roads and airfields that bear weight.

Defining Soil Compaction

• Compaction involves reducing the volume of voids within soil without decreasing the volume of solid soil grains. This process enhances overall stability.

Mechanisms of Soil Densification

• Compressive mechanical energy is applied to soil using specialized equipment to increase density or reduce void ratios. This technique is typically used on soils that have been disturbed or reapplied at a construction site.

• The process increases bulk density by mechanically densifying soil; it reduces void space while maintaining air content but cannot compact saturated soils effectively.

Benefits of Increased Soil Density

• Higher density in soil mass leads to increased stability and resolution, decreased permeability, reduced water seepage, and minimized swelling and shrinkage issues.

Advanced Compaction Techniques

• Pertamina deep vibrow represents a deep compaction ground treatment technique aimed at densifying granular soil in situ through vibrating probes or vibro floors. This method allows for simultaneous compaction across various depths.