Hazards Associated with Civil Engeering Developments

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Hazards Associated with Civil Engineering Naturally, all slope stability problems are reduced and trees such as rowan, poplar and ash bind the
Developments by efficient drainage. This minimises the pore- soil and keep the levels of soil moisture at a
water pressure. Loose materials can be dealt with constant by taking up water.
Rock Engineering: by forming them into very shallow slopes, by Rock falls may be prevented by wire mesh to
The engineering properties of rocks and planting vegetation to bind them together and to steep slopes, or fences are build across slopes to
superficial material involve a range of factors;- remove water or by covering them in netting or catch falling rocks.
- Strength in foundation- the resistance fabric. This is reprofiling.
of the material to compression. Dams and Reservoirs:
- Strength on slopes and in tunnels- the Rock slides can be prevented by building The geology of a dam is rarely ideal. The best
resistance of unsupported materials to retaining walls of materials such as concrete or site will be chosen but there will always be
failure. of gabion (rectangular wire mesh boxes filled geological problems to overcome. Thus, a range
with boulders). of thorough geological investigations is necessary
- Resistance to abrasion- resistance to Rock falls can be prevented by using rock bolts in planning a dam and the reservoir that will
the erosive effects of water currents in to tie the loose rocks into firmer rock walls. result. These will fall into six main areas;-
rivers and on coasts.
1. Hydrological factors-
- The likelihood of events such as Tunnels have special problems due to the geology/topography/vegetation/soil.
earthquakes. confining pressure of the overlying rocks. 2. Sedimentation problems- erosion
Confining pressure is caused by the mass of rates/volume of sediment in rivers.
Under high pore-water pressure the grains in a overlying materials but acts in all directions in the
rock are forced apart, reducing cohesion and same way that water presses all around a
3. Stability of the sides- angle of slope/dip
making them more likely to fail. submarine and not just its upper surface. direction.
Water can be concentrated along impermeable Arch or cylinder shapes can withstand confining 4. Groundwater movement/leakage- water
beds, causing them to lose cohesion or along pressures in rocks in the same way as table/porosity/permeability.
fracture surfaces, causing them to slip. submarines, whose hull is curved to withstand the 5. dam foundations
pressures. 6. construction materials
Geotechnical investigation is carried out on all In tunnels without reinforcements, the ground
major construction sites, in particular to can swell up from below, some old mine The permeability of rocks can be reduced by
establish whether the foundation material is tunnels have completely closed up in this way. expensive clay or plastic linings or by grouting.
likely to be prone to compaction, swelling, If the tunnel sides are unsupported, they do can There are particular problems when dams are
rotational slip or sliding. Clays are particularly fail dramatically in rock bursts. Tunnels are more sited on permeable rocks because the height of
affected by compaction. Expansion of clays and greatly affected by pore-water pressures than the water behind the dam greatly increases
other materials that swell when they absorb other excavations, so good drainage system is groundwater pressures.
water can also cause problems if the water rises essential. Thus, the potential for leakage is much greater
into them during construction. and sometimes water paths through permeable
Cuttings and Embankments: rocks can be so widened that the dam is
When there are problems like this, the solution Cuttings and embankments are made for roads, weakened and collapses.
can include spreading the load of construction railways and canals, and produce steep, Where rocks are permeable, a trench is normally
using rafts of concrete or the sinking of unstable slopes. To improve stability, the slope excavated in the rock beneath the dam site and
concrete piles to firmer foundation rocks can be cut in a series of steps or material can be filled with impermeable material; this forms an
beneath. Drainage system can be installed to moved from areas where slippage could occur to underground barrier to groundwater flow and is
reduce pore-water pressure problems. lower, more stable areas. called a cut off curtain.
The slope must be thoroughly drained to prevent
Slopes and Tunnels: the movement of water-logged material. Often, All dams leak to some degree, because of the
All slopes can be subject to failure, whether stone-filled drains are arranged in a herring-bone large water pressures involved, but dams are
natural hillsides or cliffs, excavated cuttings pattern on the slope. successful where loss of leakage and evaporation
or tunnels, or constructed embankments. The slope may be surrounded by retainer walls, is much less than the water gain from the
or by piles driven into the rock. Retaining walls catchment area.
must have drainage channel at their bases. Grass


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