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Foundations

Jet Grout Soil Nailing
civil techniques

Jet Grout Soil Nailing

23 Mar, 2018

The Jet Grout Soil Nailing method use for eroding the soil for creating holes in the slope surface. Steel bars install in this hole and grout with concrete. It provides good corrosion protection for the steel bars. Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of steel reinforcing bars.

Jet Grout Soil Nailing

Soil nailing uses to stabilize existing slopes and excavations. The top-to-bottom construction is advantageous compares to the other retaining wall systems.

As construction proceeds from the top to bottom, shotcrete or concrete applies to the excavation face to provide continuity. In short Soil, Nailing increases the shearing resistance of soil by acting in tension.

In the present construction times, soil nailing employes large in railway construction work. It uses for the stabilization of side lopes in existing track-road. And laying of new tracks adjoining to an existing one.

Types of Jet Grout Soil Nailing

There are three types of Jet Grouting Soil Nailing, they are,

  • Single fluid jet grouting
  • Double fluid jet grouting and
  • Triple fluid jet grouting.

1. SIngle fluid jet grouting

In this Single fluid jet grouting, the grouting takes place by using grout.  In this method of the single jet grouting, the grout force into the soil with the very high-speed mechanism. And grouting carries out.

2. Double fluid jet grouting

In Double fluid jet grouting, the grouting takes place by using Air and grout.  In this method of the double jet grouting, the grout and air force into the soil with the very high-speed mechanism.

3. Triple fluid jet grouting

In Triple fluid jet grouting, the grouting takes place by using Air, Water, and grout. In this method of the triple jet grouting, the grout, air, and water forces into the soil with the very high-speed mechanism.

Soil Nailing
Foundations

Soil Nailing

23 Mar, 2018

Soil nailing is a construction technique to reinforce soil to make it stable and strong. Soil nailing technique uses for slopes and excavations alongside highways, railway lines. It uses for, excavations, retaining walls slopes, to make it more strong and stable.

The soil reinforces with slender elements like reinforcing bars name as nails. These reinforcing bars install into pre-drill holes and grouts. The nails install at an inclination of ten to twenty degrees with vertical reinforcement.

Soil Nailing employes when requiring slopes for excavation cannot provide due to space constraints. And employes in the construction of retaining wall. It is an alternative to retaining wall structures.

Soil Nailing

At excavation, the shotcrete, concrete and grouting materials apply to the excavation face to grout the reinforcing steel and nails. It provides stability to the steep soil slope.

Types of Soil Nailing:

There are various types of soil nailing techniques:

  • Grouted Soil Nailing
  • Driven Nails
  • Self-drilling Soil Nail
  • Jet Grouted Soil Nail
  • Launched Soil Nail

1. Grouted Soil Nailing

In this type, the holes drills in walls or slope face and nails inserts in the pre-drill holes. These holes fill with grouting materials like concrete and shotcrete.

2. Driven Nails:

Driven nailing use for temporary stabilization of soil slopes. In this method, the nails drive in the slope face at the time of excavation. This method is very fast. It does not provide corrosion protection to the reinforcement steel and nails.

3. Self-drilling Soil Nail:

In this method, the hollow bars use. Hollow bars drills into the slope surface and grout inject simultaneously during the drilling process. This method of soil nailing is faster than grout nailing. This method provides more corrosion resistance to nails than driven nails.

4. Jet Grouted Soil Nail:

In this method, jets use for eroding the soil for creating holes in the slope surface. Steel bars install in this hole and grouts with concrete. It provides good corrosion protection for the steel bars and nails.

5. Launched Soil Nail:

In this method, the steel bars force into the soil with high speed using compressed air mechanism. The installation of soil nails is fast. And control over the length of bar penetrating the ground is difficult.

Footings
civil techniques

Footings

7 Apr, 2018

Footings designs to resist the shear force causes by imposing loads. Footings constructs in open space and known as open foundations. It provides with natural slopes on all sides. It employs for a depth up to 5 m. The base of the structure enlarges or spreads to provide individual supports. These type of foundations provides for the structure of moderate heights built on the dry ground.

footings

Types of footings

  • Wall Footing
  • Isolated footing
  • Combined footing
  • Inverted footing
  • Continous footing
  • Cantilever footing
  • Grillage footing

1. Wall Footing

Footings are of simple or stepped on wall footing. The base course of the footings is of concrete or other material. These footings employ only for simple structures. It has one projection beyond the width of the wall on sides. The width of the concrete base is equal to twice the width of the wall. In single footings, the brick footing is widely employing.

2. Isolated or column footing

footings

It uses to support individual columns. It is in step or has a projection in the concrete base. In heavy loads, steel reinforcement provides in both directions in concrete bed. An offset of 15 cm provides on all sides of the concrete bed. In brick masonry, offset is of 5 cm on all sides in regular layers.

3. Combined footing

footings

A combined footing supports more columns in a row. The combined footing is of rectangular shape if both the column carry equal loads. In unequal loads it of trapezoidal shape. It is rigid and resisting on the homogeneous soil.

4. Inverted arch footing

Inverted arch footing use on the soft soil to reduce the depth of foundation. Loads above an opening transmit from supporting walls through inverter arches of soil. In this type of footing, the end columns are stable enough to resist the outward pressure causing by arch section.

5. Continuous footings

In this type of footing, a single continuous R.C. slab provides a foundation of more columns in a row. It is suitable for locations liable to earthquake activities. This prevents differential settlements in structure. To have a better stability deeper beam constructs in between columns.

6. strap or cantilever footing

It consists of more individual footings connects by a beam known as a strap and known as cantilever footing. This type of footing uses where the distance between the column is greater. It serves to transfer column loads on the soil with equal and uniform soil pressure.

7. Grillage footing

This type of footings uses to transmit heavy loads from steel columns to the soils having low bearing power. This type of arrangements avoids deep excavation. And provides a necessary area at the base to reduce the intensity of pressure. Grillage footings are of roll steel joists and name as grillage beams to providing in single or double tires.

Retaining Walls
Concrete Structures

Retaining Walls

7 Apr, 2018

Retaining walls

Retaining wall prevents the earth from sliding or eroding away. And to resist the material pressure of the material that it is holding back. It constructs with heavy blocks, angled stones, offset cinder blocks, wood or reinforced concrete frames backfilled or filled with the well-graded stone designed to create the geological resistance or mass required to counteract the earth pressures and surcharge loading. And also, anchor into the ground with steel I beam vertically inserted into the ground and reinforced with concrete and linked in between with planks or reinforced, Pre-fabricated concrete blocks.

retaining wall

Types of Retaining wall

Classification of retaining walls:

Following are the different types of retaining walls based on the shape and the mode of resisting the pressure.

  1. Gravity wall-Masonry or Plain concrete
  2. Cantilever retaining wall-RCC (Inverted T and L)
  3. Counterfort retaining wall-RCC

1. Gravity wall – Masonry or Plain concrete

Retaining Walls

Gravity retaining Wall constructs of concrete, stone or brick masonry and are thicker in section. The geometry of these walls also helps them to maintain the stability. Mass concrete walls are suitable for retained heights of up to 3 m. The cross-section shape of the wall affects by stability, the use of space in front of the wall, the require wall appearance and the method of construction.

Retaining Walls

2. Cantilever retaining wall-RCC (Inverted T and L)

retaining wall

A cantilever retaining wall is one that consists of a wall which connects to the foundation. They are the most common type engages. Cantilever wall rest on a slab foundation. A cantilever wall holds back a significant amount of soil. It consists of a stem, toe slab, and heel slab.

3. Counterfort retaining wall-RCC

retaining wall

counterfort types adapted to larger heights. It consists of a stem, toe slab and heel slab as in case of cantilever retaining wall. But it also consists of counterforts are a regular interval which divides the stem. The stem with the combination of counterfort behaves like a tee-beam with varying width. The stem and heel slabs are effectively fixed to counterforts so that the stem bends horizontally between the counterforts due to lateral earth pressure. Thus the thickness of stem and the heel slab is considerably reduced due to the reduction of the moment due to fixity of these slabs between counterforts.

Pile Driving Equipment
civil techniques

Pile Driving Equipment

7 Apr, 2018

Pile Driving Equipment

Pile Driving Equipment uses to drive piles in the weak soil for providing strong grip to foundations. The process of forcing a pile into the ground is pile driving. The piles drive vertically into the earth.

The equipment required for pile driving is as follows

  • Pile frames
  • Pile hammers
  • Leads
  • Winches and
  • Miscellaneous.

1. Pile frames

The pile frames are generally of steel having a height varying from ten to twenty-five meters and more. Pile frames are light and easy to transport. It consists of platforms for supporting drivers, engines, winches, etc.

2. Pile hammers

The function of hammers is to impart energy to drive the pile into the soil. These hammers guides between two steel members known as leads. Heavy conventional hammers drive pile by an impact. Vibratory hammers evolve as to avoid noise pollutions by driving piles by vibration.

PILE TYPES

3. Leads

Leads employ to guide hammers and piles. For drop hammers, fixed leads are uses. Leads are movable and adjustable as per use. Leads are more convenient.

4. Winches

Winches require for lifting the hammer and pile. These are of a light type with a single drum or heavy type with a double or triple drum. And it fits with reversing gears. Drop hammers, pneumatic hammers, winches operate by diesel, petrol, and electric engines. For steam hammers, use steam-power winches to lift the hammer and pile.

5. Miscellaneous

 

Pile Driving Equipment

The other equipment requires for the process of pile driving are pile extractors, followers, jetting equipment, steam engines, air compressors.

  1. pile extractors are for pulling piles from the ground after its impaction to a connection of reinforcement to foundations.
  2. followers are connecting pieces of wood or steel between hammer and top of a pile. It is to transmit energy from the hammer to pile in underwater pilling.
  3. jetting equipment is necessary to discharge water jets at high pressure to assist driving piles into sand or fine gravel.
PILE TYPES
Concrete Structures

PILE TYPES

7 Apr, 2018

PILE TYPES BASED ON CONSTRUCTION METHOD

Three pile types of pile foundations according to their construction methods:

  1. Driven piles,
  2. Cast-in-situ piles, and
  3. Driven and cast-in-situ piles.

1. Driven Pile Foundations:

It is of concrete, steel or timber. These piles are prefabricating before placing at the construction site. If drive piles are of concrete, they are precast. These piles are drive using a pile hammer.

PILE TYPES

When piles drive into the granular soils, they displace the equal volume of soil. This helps in compaction of soil around the sides of piles and results in the densification of soil. The piles which compact the soil adjacent to it is compaction pile. This compaction of the soil increases its bearing capacity.

Saturated silty soils and cohesive soils have poor drainage capability. So these soils are not compacts when piles are drill through it. The water is to be a drain on the soil to be compact. Stresses develop adjacent to the piles have to be borne by pore water only. This results in an increase in pore water pressure and a decrease in bearing capacity of the soil.

2. Cast-in-situ Pile Foundations:

Cast-in-situ piles are the concrete pile. These piles construct by drilling holes in the ground to the required depth. And then filling the hole with concrete. Reinforcements utilize in the concrete as per the requirements. These piles are of small diameter compare to drill piers.

 

Cast-in-situ piles are straight bore piles or with one or more bulbs at intervals are cast. The piles with one or more bulbs are under-reamed piles.

3. Driven and Cast-in-situ Piles

Driven and cast-in-situ piles have the advantages of both driven and cast-in-situ piles. The procedure of installing a driven and cast-in-situ pile is as follows:

A steel shell of the diameter of a pile driven into the ground with the aid of a mandrel inserting into the shell. After driving the shell, the mandrel removes and concrete pours into the shell.

The shell is of corrugate and reinforces thin sheet steel or pipes. The piles of this type are shell type piles.

The shell-less type formes by withdrawing the shell while the concrete places. In both the types, the bottom of the shell is close to a conical tip which separates from the shell. By driving the concrete out of the shell an enlarge bulb form in both the types of piles. Th shells left in place and the tube concretes. This type of pile is very much use in piling over water.

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