WorksheetsRetaining Walls, Slope Stabilisation, GW Control & Excavations
Total questions: 20
Worksheet time: 10mins
1. What is the main goal of groundwater control during excavation?
To remove all water from the ground
To lower the water table below bedrock
To keep the excavation dry, stable, and safe
To maintain water at natural levels throughout construction
Which of the following best describes a “perched water table”?
Water that seeps from groundwater drains
A small, trapped pocket of water above the main water table
The top of the water table in bedrock
Water confined under artesian pressure
Which Irish legislation specifically covers safety in excavations?
Building Control Regulations 2014
Safety, Health and Welfare at Work (Construction) Regulations 2013
Health and Safety at Work Act 2005
Building Regulations Part C
Which of the following retaining walls relies mainly on its own weight for stability?
Cantilever wall
Counterfort wall
Gravity wall
Secant pile wall
Which slope stabilisation method involves drilling and grouting steel bars into the ground?
Soil nailing
Grouting
Surcharging
Compaction
What type of shoring system uses interlocking steel sections driven into the ground?
Soldier pile and lagging
Timber shoring
Steel sheet piles
Diaphragm wall
Which dewatering method is best suited for shallow excavations in coarse, free-draining soils?
Sump pumping
Wellpoint system
Deep wells
Ground freezing
Which type of retaining wall is constructed before excavation begins, forms part of the permanent basement structure, and provides a watertight reinforced concrete wall for deep excavations?
Diaphragm wall
Soldier pile and lagging wall
Sheet pile wall
Reinforced soil wall
Which statement about counterfort and buttressed retaining walls is correct?
Counterforts are placed on the front face of the wall
Buttresses are placed on the soil side
Counterforts are at the back, buttresses at the front
Both types are used only for low-height walls
Which slope stabilisation method primarily aims to reduce pore water pressure and improve stability before construction?
Soil replacement
Surface and subsurface drainage
Surcharging
Soil nailing
What is the main purpose of a grout curtain?
To collect groundwater for reuse
To form a low-permeability barrier that prevents water flow
To strengthen concrete walls
To cool the soil and prevent swelling
Which of the following best describes a soldier pile and lagging system?
Concrete diaphragm wall constructed under slurry
H-section steel piles with horizontal timber or concrete lagging
Reinforced soil wall using geogrids
Sheet piles driven into the ground using a vibro-hammer
In the context of soil improvement, “surcharging” is used to:
Replace soft soils with granular fill
Improve drainage and slope stability
Pre-consolidate soft ground by applying a temporary load
Chemically stabilise weak soils
You are supervising a basement excavation in sandy soil. The excavation depth is 4 m, and minor groundwater seepage is visible. Which method would be most appropriate to control water?
Deep well system
Wellpoint system
Ground freezing
Grout curtain
During a trench excavation, workers notice base heave due to high groundwater pressure. What is the most likely cause?
Inadequate strutting
Insufficient sump depth
Excess upward pore pressure under the base
Surface water infiltration
A site has limited space, nearby buildings, and vibrations must be minimised. Which retaining wall type is most suitable?
Contiguous bored pile wall
Sheet pile wall
Gravity wall
Buttressed wall
Which of the following slope stabilisation methods primarily strengthens soil through chemical reaction?
Lime/cement stabilisation
Soil replacement
Compaction
Surcharging
A bridge pier foundation is being built below river level. The contractor needs to work in the dry. Which structure will they most likely use?
Cofferdam
Caisson
Diaphragm wall
Secant pile wall
Which of the following statements are TRUE regarding the risks of excessive dewatering? (Select TWO)
It may cause settlement of nearby structures
It can undermine nearby foundations by removing supporting groundwater pressure and reducing soil strength
It always improves slope stability
It prevents base heave completely
A contractor installs a secant pile wall around an excavation and also places sump pumps inside the enclosure to remove any seepage that enters. What type of groundwater-control system is being used?
Dewatering system only
Exclusion system only
Combined system (exclusion + dewatering)
Passive drainage system
