Objectives & Methods of River Training Works

Definition of River Training

The process of controlling the flow in river & river bed configuration is called river training works. These are the structural measures adopted in rivers to avoid outflanking & shifting its thalweg due to geomorphological changes in the river. So, the river training works stabilize the river channel along a certain alignment.

Methods of Soil Compaction | Types of Soil Compaction

Compaction of soil is necessary for various types of foundations used in civil engineering constructions. It improves the engineering properties of soil. Compaction is the process of reducing air voids in soil by means of mechanical compressions. During compaction, the air is expelled from the voids in the soil. It increases the dry density of soil, improves shear strength & hence stability and bearing capacity. The various methods of soil compaction are as follows:

• Tamper / Rammer
• Hand Operated Tamper
• Mechanical Tamper
• Roller
• Smooth Wheeled Roller
• Pneumatic Tyred Roller
• Sheep Foot Roller
• Vibrator

Types of Foundation Used in Civil Engineering Constructions

Every civil engineering structure, whether it is a building, a bridge, or a dam, is founded on or below the surface of the earth. Foundations are required to transmit the load of the structure to the foundation soil safely & efficiently. Different types of foundations used in civil engineering constructions can be classified as follows:

Shallow Foundation

According to Terzaghi, a shallow foundation is one whose width is greater than its depth. i.e. Df/B<1. Such a foundation transmits the load to the upper strata of the earth & is generally provided to the lightweight structures. It is preferred when foundation soil has sufficient bearing capacity at shallow depth. When the sum of areas covered by each isolated footings is more than 50% of the total area of the foundation, mat foundation is adopted.

Strip or Wall Footing

Isolated or Spread Footing

Combined Footing

Strap or Cantilever Footing

Mat or Raft Foundation

Deep Foundation

A deep foundation is one whose width is less than its depth i.e. Df/B>1. Such a foundation transmits the load to the strata at a considerable depth below the surface of the earth & is provided to the heavyweight structure. It is preferred when the soil at the surface of the earth does not possess a considerable bearing capacity. The most common types of deep foundations are piles, piers & caissons. Well foundations are the special case of open caissons.

What are the Criteria for Selection of Ideal Bridge Site?

It is necessary to select an ideal bridge site at which the bridge can be made economically. As construction of a bridge requires a heavy investment, the bridge site should be selected wisely. A poor bridge site may increase the project's cost, making it susceptible to damage, in the long run, thus decreasing the life span of bridges. Thus, the following are the factors that require attention while selecting a bridge site.

Principles & Techniques of Bioengineering for Civil Engineers

In a broader sense, Bioengineering is the use of life science & engineering to solve human life problems. Here, in this article, we are using the term bioengineering in the context of civil engineering & it basically refers to soil bioengineering. So, Bioengineering can be defined as the use of vegetative measures & small civil engineering structures in order to reduce the shallow seated instability. The living plants or non-living plant materials are used alone or in conjunction with small civil engineering structures for slope stabilization & erosion control. It utilizes locally available resources & is a cost-effective method.

Principles of Bioengineering

Initially, stability is obtained from the small civil engineering structures. The strength of those structures decreases gradually. After the handover point, stability is derived from the vegetative measures. This can be depicted from the graph shown below:

Functions of Bioengineering

Engineering functions performed by vegetation on a slope are as follows:

• Catch
• Armor
• Reinforce
• Anchor
• Support
• Drain

Advantages of Bioengineering

• Immediate slope stabilization & erosion control
• Utilization of locally available resources (local tools, local manpower, local materials)
• It is a cost-effective method
• No need for frequent maintenance
• It also provides an opportunity for wildlife habitat
• It also improves the aesthetic beauty of the site

Commonly Used Techniques of Bioengineering

• Fascine: Bundle of live branches laid in shallow trenches
• Palisade: Woody cuttings planted across the slope.
• Wattling: Fence made out of vegetative materials.
• Bamboo Planting: Planting of bamboo for soil conservation
• Grass Planting: Planting of grass across the slope
• Brush Layering: Layers of woody cuttings planted in line following the contour
• RipRap: Stone pitching with vegetation interplanted between them
• Retaining Wall: Wall built to resist the pressure of earth filling or backing
• Toe Wall
• Breast Wall or Revetment Wall
• Check Dam: Dams constructed across the gullies to retard the flow
• Gabion Wall: Walls made up of gabion wire filled with stones
• Stone Masonry: Masonry construction using stones & mortar 
• Jute Netting: Protecting the slope with standard jute mesh
• Rock Netting: Wire mesh of reliable material used to control the rockfall
• Rock Bolting: Reinforcement of rock slope by inserting steel bars
• French Drain: Subsurface drainage channel filled with aggregates