Question

The urban tram project, which operates with a light rail system, is planned. In addition to metaformic, sedimentary and magmatic rocks on the ground, unconsolidated fine sand-silt grain size ground materials were also found. Underground water level depth is between 1 and 3 meters. There is a fault zone along the project line. What can be the geotechnical problems that may be encountered before, during and after the project construction, and solutions as a civil engineer?

Answer 1

A civil engineer cannot burry his mistakes in a grave like a doctor, neither can he hide it with greenery like an architect nor can he justify it with philosophical justifications like a philospher.

The various problems of the project before the construction are;

• Fault location studies to evaluate the presence of active faulting and fault rupture potential
• Deterministic and probabilistic seismic hazard analyses to evaluate potential earthquake magnitudes and anticipated ground accelerations, and to provide seismic design recommendations to the project design team
• Evaluation of the potential impacts of shallow subsurface ground water conditions on the planning, design, and construction phases of a proposed development
• Hydrological studies to identify the groundwater conditions for water resource potential, design construction dewatering, and assessment of hazards related to slope stability and liquefaction potential

The expected problems during the course of construction and after the construction are;

• There is every possibilty of liquefication during construction
• Metamorphic rocks are prone to swelling and shrinkage and during construction it can cause alignment issues
• optimum moisture content can vary drastically since we have unconsolidated fine sand
• Any earthquake having" peak ground acceleration "greater than design value can impact the "base shear "and can give headache to geotechnical engineer

As a geotechnical engineer , we are born to accept challenges and create marvels out of nothing. the possible solutions to above problems are;

• A detailed geotechnical investigation will high class of accuracy will considerably help to minimize the problems
• proper compaction of weak zones across the alignment will resolve the issues like liquefication
• use of "geo-composites" will stabilize the weak soil and can reinforce the foundation
• the critical zones in the weak rocks can be strenghtened by "rock bolting"
• "soil-nailing" can do wonders at minimal relative cost
• the issue of high water table can be resolved by drawing out the water using pumps and this water can be utilized for irrigation and industrial demands
• use of strain energy dissapiation mechanisms can be fruitful since the alingnment is across a fault line
• proper drainage will restrict the increase of unit weight of soil and will arrest the increase of effective stress