NCERT Solutions for class 10th Social Science Chapter 33 Safe Construction Practices

Exercises

Question 1. What should be the configuration of an earthquake resistant building?

Answer : The configuration of an earthquake resistant building should be as follows
(i) The building should have a simple rectangular plan.
(ii) Long walls should be supported by Reinforced Concrete columns.
(iii) Large buildings having plans with shapes like T, L, U an d X should preferably be separated into rectangular blocks by providing gaps in between.

Question 2. How should the foundation be constructed in soft and firm soil?

Answer : Buildings which are structurally strong to withstand earthquakes sometimes fail due to inadequate foundation design. Tilting, cracking and failure of the structure may result from soil liquefaction. Soil liquefaction means transformation of soil from a solid state to a liquid state as a consequence of increased pressure. Depending on the type of soil conditions, the depth of the foundation should to be decided .

Question 3. Which are the most vulnerable homes due to flood?

Answer : The most vulnerable homes due to flood are
(i) Buildings which are constructed with earth-based materials or using stone and brick in mud mortar are highly vulnerable to damage in heavy rains and/or floods.
(ii) The huts made from biomass materials like bamboo, leaves, thatch or light construction using metal sheets are easily destroyed in floods and washed away.

Question 4. What are the general protection measures for buildings against flood damage?

Answer : The most effective measures for prevention against flood are

  • Avoid constructing buildings on river banks and slopes on river sides and the sides of gorges.
  • Build at least 250 meters away from the seacoast/river banks.
  • Build proper drainage system in all flood prone areas, so that the water can be drained off quickly to prevent accumulation.
  • Construct the building with a plinth level higher than the known high flood level.
  • Construct the whole village or settlement on a raised platform higher than the high flood level.
  • Construct buildings on stilts or columns with wall-free space at ground level permitting free flow of water (inundation or flowing), provided that the columns are circular and strong. In dry weather condition the ground area could be fenced and used for cattle , sheep, poultry farming, or storage etc.

Question 5. What are the considerations for selecting the site in areas prone to landslides?

Answer : Landslides generally happen where they have occurred in the past, and in identifiable hazard locations. Areas that are typically considered safe from landslides include areas that have not moved in the past; relatively flat areas away from sudden changes in slope and areas at the top of or along ridges. Houses built at the toe of steep slopes are often vulnerable to slides and debris flows.

Question 6. Write about the slope stabilization methods by drainage.

Answer : There are three methods for doing this

  • Protect Vulnerable Areas Keep surface drainage water away from vulnerable areas, such as steep slopes, loose soil and non-vegetated surfaces.
  • Collect Runoff Collect and direct water from verandahs, driveways and non-vegetated surfaces into catch basins; confine water flow in drainpipes such as a drainage ditch, dry well, gutter, natural drainage or holding pond. Roof water may go directly to the drainpipe.
  • Intercept Surface Water When surface water flows onto your property, and where a discharge point is available, dig a shallow, gently sloping ditch to intercept the water and direct it into a natural water course, vegetated drainage area, road pavement or road drainage ditch. Your intercepting ditch should be nearly horizontal, with a minimum slope, sufficient to allow water to flow slowly. Smoothen the sides of the ditch and grow vegetation; keep all ditches free of debris.

Question 7. What are the desirable plan-forms and orientations for cyclone resistant buildings?

Answer : The desirable plan forms and orientations for cyclone resistant buildings are

  • For individual buildings, a circular or polygonal plan shape is preferred over rectangular or square plans.
  • A symmetrical building with a compact plan form is more s table than an asymmetrical building with a zig-zag plan having empty pockets, as the latter is more prone to wind/cyclone related damage.

Question 8. What kind of roof designs should be used in cyclone prone areas and why?

Answer : The following kind of roof designs should be used in cyclone prone areas
(i) The overall effect of wind on a pitched roof building and the critical locations are shown in the figures given below Therefore,
the roof projections should be kept minimum, say not exceeding 500 mm, or else, are tied down adequately.

(ii) For the purpose of reducing wind forces on the roof, a hipped or pyramidal roof is preferable to the gable type roof as shown in the figure given below.
Therefore the roof protections should be kept minimum, say not exceeding 500 mm, or else, are tied down adequately.

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