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Presentation on theme: "CONSTRUCTION OF SOIL NAILING WALLS"— Presentation transcript:

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2 Contents Subsoil considerations Design consideration
Construction considerations Construction and installation steps Advantages Disadvantages

3 Subsoil Considerations
Favorable Conditions Soil should be stiff or hard with fine grains Grains should have low plasticity Soil should have natural cohesion provided by either capillary water of natural cementation Subsoil with weathered rock should be uniformly weathered

4 Subsoil Considerations
Unfavorable Conditions Dry and poorly grained soils Soils lacking natural cohesion or cementation Soil with a lot of ground water Soil with a lot of cobbles and boulders Soil that is not uniformly weathered Highly corrosive soils

5 Design Considerations
Drainage considerations Use of geo-composite drain strips along the excavation walls to allow water to be discharged through weep holes at the bottom of the wall Use of drain pipes to control ground water pressure. Designing ditches behind the walls to prevent surface water from infiltrating behind the walls

6 Design Considerations
Other considerations They should be designed to resist damage caused by frost action by increasing thickness of soil wall be using porous material The wall should be designed in a way that it can withstand both external loads such as highways and the weight of the temporary facing.

7 Construction Considerations
The state of the construction material should be in good physical conditions and as per the design specification Check to ensure the excavation walls are stable and that the nails are properly installed with the right length size and spacing Check to ensure the completed soil wall is not tampered with during excavation of the next phase

8 Construction Considerations
The contractor should ensure that the soil nail drilling is done as per the specifications The amount of time the drill holes remain open to avoid caving Materials are properly handled to avoid damages Ensure nails are properly grouted in the grouted column with no gaps left

9 Construction and Installation Steps
Excavation is done to a level the walls can support themselves for 2 days. It is made about 6feet and wide enough for equipment Drilling the nail holes according to the design specifications Installing the nails using centralizers together with pipes filled with grouting cement. Geo-composite walls are also installed in this phase.

10 Construction and Installation Steps
4. Construct temporary facing to support the open cut soil using a reinforced layer of welded wire mesh between the facing thickness Construction of subsequent levels by repeating steps 1- 4 Finally construct a permanent facing using reinforced concrete and fabricated panels

11 Advantages of Soil Nail Walls
Construction advantages Doesn’t disrupt the flow of traffic as compared to other methods It provides a less congested excavation bottom It has a rapid construction schedule The design can be easily adjusted without creating safety issues

12 Advantages of Soil Nail Walls
Performance Resultant wall are very flexible The structures have very small deflections The walls can withstand seismic activities Cost Overall cost is lower than other methods Uses cheaper materials such as shortcrete

13 Disadvantages of Soil Nail Walls
Can be implemented by highly trained and experienced contactors only. It is not favorable in areas with a lot of ground water The presence of different utilities pose a challenge in terms of inclination and length of the soil nails during construction in the upper rows

14 END


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