geology in roads

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Geology in road constructions : 

Geology in road constructions

Introduction : 

Introduction Roads important for any country and its development. Major duties of civil engineer- Design Planning Construction Maintenance

Geological investigations provides : 

Geological investigations provides Topography Lihthological Character of rocks or soil Geological Structures.

topography : 

topography Single most important factor It reveals existence of land features Knowledge of topography is essential To decide cuttings To give retaining walls To obtain topographical details Preliminary Surveys Aerial Surveys

Lithological character : 

Lithological character Geological surveys should provide details like Composition of rocks Texture of rocks Structure of rocks Origin of rocks

Slide 6: 

Massive groups of rocks Can stand even with vertical slopes Requires blasting operations Stand erect year without much maintenance Unconsolidated group Requires soil investigations Investigation of clay layers at critical places

Geological structures : 

Geological structures Structural features of rocks have very important bearing upon Design of cuts Stability of road Structural features of rocks Dip & Strike Joints Fault planes Shear zones

Dip and strike : 

Dip and strike 1) Cut is parallel to the dip direction. Offers a uniform behavior on either side of the cut. Risk of failure is minimum.

Slide 9: 

2) Cut is made parallel to the strike. Right angles to dip direction results in plunge of strata. On dipping side there is always likelihood of slips

Slide 10: 

3) Cutting inclined to dip and strike Strata will dip across cutting and the slope of cutting will be unequal on both sides. Measures include: Enlarging of section Provision of retaining wall Very effective drainage system

Joints and faults : 

Joints and faults JOINTS Influence the stability of cuts Jointed rocks have to be provided artificial supports by breast walls and retaining walls for ensuring stability. FAULTS Crushing of stones along fault planes and shear zones Very unfavorable condition for cut. Worst type of potential failure.

WEATHERING Softer layer of rock get weathered at a faster rate than the overlaying harder rock. Cause slip or falls of whole face. Cleaning of slopes from loose debris and flattering for avoiding debris shall be needed. Constructing concrete walls against fracture zones.

Slide 13: 

GROUNDWATER CONDITIONS Necessary to investigate thoroughly the position of water table. Water exerts influence on the bearing capacity of the rocks and soil. In case of ground with rich moisture, properties of ground have been determined. Condition of free-flow of groundwater through the soil is quite dangerous.

Slide 14: 

ROADS IN HILLY AREAS. Shortest alignment is difficult. Aerial surveying is necessary. Structural features of rocks have to be considered. ROADS IN WATER LOGGED AREAS. Roads get deformed and damaged . Measures:- 1)Lower down the water table. 2)Increase thickness of road crust.

Slide 15: 

ROADS IN MARSHY REGIONS Failure due to subsidence might be the threat to the stability of the road. Geological investigation should reveal presence of unstable material at critical depths. Treatment:- 1)Excavate the weak soil or other such material and replace it with sound material. 2)Inducing strength by artificial means. 3)Effective drainage system.

Slide 16: 

ROADS IN PERMAFROST REGIONS. When a road is constructed over a frozen ground, the warm fill material acts as a blanket over the intergranular below and thus causes its melting, which causes subsidence because the soil below becomes temporarily saturated. Treatment:- A well planned insulating layer should be given in between the warm fill of the road surface and the ice below.



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