Test 39 - Geological Hazards and Preventive Measures

Question 1 ప్రశ్న 1

A proposed water-supply installation lies below a slope mapped as highly susceptible to landsliding. Which statement correctly distinguishes landslide susceptibility from landslide risk?

A Susceptibility directly expresses the monetary loss expected from every future landslide. B Susceptibility describes the relative tendency of ground to undergo landsliding, while risk also considers hazardous events, exposed assets and their vulnerability. C Risk depends only on the inclination of the slope and not on the infrastructure exposed. D A high-susceptibility classification proves that a landslide will occur on a specified date.

Question 2 ప్రశ్న 2

A highway authority uses a Geological Survey of India landslide-susceptibility map to screen a proposed hill-road corridor. Which interpretation of the map is most appropriate?

A The map gives the exact date and volume of the next landslide at every location. B A regional susceptibility map removes the need for engineering-geological investigation of individual road cuts. C The map can identify areas requiring more detailed investigation, but local geology, slope conditions and construction effects must be assessed before design. D A low-susceptibility map category guarantees that no rainfall-induced slope failure can occur.

Question 3 ప్రశ్న 3

A soil slope develops a spoon-shaped failure surface concave upward, and the displaced mass moves downward while rotating backward near its head. Which mass-movement mechanism is indicated?

A Rotational slide or slump. B Planar translational slide along a straight bedding surface. C Rockfall involving free fall from a cliff. D Forward toppling of an isolated rock column.

Question 4 ప్రశ్న 4

A rock mass on a hillside moves downslope approximately as a coherent slab along a persistent, nearly planar bedding surface. Which classification is most appropriate?

A Rotational slide with an essentially circular failure surface. B Debris flow characterized by slurry-like movement. C Toppling involving forward rotation about a pivot near the base. D Translational rock slide controlled by a geological discontinuity.

Question 5 ప్రశ్న 5

Following intense rainfall, a steep drainage channel carries a rapidly moving mixture of water, soil, rock fragments and organic material toward a road crossing. Which hazard and mitigation approach are most appropriate?

A A conventional dry rockfall; only strengthening the road pavement is necessary. B A rotational slide; the road crossing cannot be affected because the material remains at the slope head. C A debris flow; investigate source areas, drainage paths and possible interception, diversion or appropriately designed protective structures. D A tectonic fault rupture; ordinary rainfall cannot influence the movement.

Question 6 ప్రశ్న 6

A highway cutting in jointed rock experiences occasional detachment of blocks that fall, bounce and roll toward the carriageway. Which combination of measures is most appropriate for managing this hazard?

A Increase the slope surcharge and remove all protective benches. B Assess scaling of unstable blocks, rock anchoring where suitable, protective mesh or barriers and adequately designed catch ditches. C Treat the hazard solely by lowering the groundwater table in a distant confined aquifer. D Assume the road is safe because the intact rock between joints has high compressive strength.

Question 7 ప్రశ్న 7

A steep rock cut contains tall, narrow rock columns separated by persistent near-vertical joints. Several columns are inclined outward and show potential forward rotation about their lower edges. What instability mechanism should be investigated?

A Rock toppling controlled by discontinuity geometry and rotational instability. B Uniform consolidation settlement of an unfractured soil deposit. C A purely horizontal strike-slip fault with no possible block rotation. D Liquefaction of saturated sand beneath a horizontal ground surface.

Question 8 ప్రశ్న 8

A river progressively erodes the toe of a natural hillside containing weathered rock and soil. What is the most important effect of continued toe erosion on slope stability?

A It necessarily increases resisting forces because the hillside becomes lighter. B It eliminates groundwater pressure throughout the slope. C It permanently increases the shear strength of the remaining weathered material. D It can remove supporting material and modify slope geometry, increasing the possibility of sliding or collapse.

Question 9 ప్రశ్న 9

A hillside remains stable during dry weather but develops tension cracks and movement after prolonged rainfall. Piezometers indicate that groundwater pressure has risen along a potential sliding surface. Which mechanism most directly explains the reduction in stability?

A Increasing pore-water pressure always increases effective normal stress and frictional resistance. B Rainfall immediately converts every soil particle into a stronger rock mineral. C Increased pore-water pressure can reduce effective normal stress and available frictional resistance along the sliding surface. D Water pressure cannot influence slope stability unless a fault passes through the site.

Question 10 ప్రశ్న 10

For a simplified planar slope-stability assessment, the total weight of a potentially sliding block is W = 1000 kN on a plane inclined at 30 degrees. Take sin(30 degrees) = 0.500 and cos(30 degrees) = 0.866. The total pore-water force normal to the plane is U = 200 kN, the cohesive resistance along the plane is cA = 100 kN, and tan(phi) = 0.50. Neglect other forces and use FS = [cA + (W cos(theta) - U)tan(phi)]/[W sin(theta)]. What is the factor of safety?

A 1.07. B Approximately 0.87. C 1.33. D 2.00.

Question 11 ప్రశ్న 11

A road embankment has developed movement along a wet, weak foundation layer. Investigation identifies surface-water entry, elevated internal pore pressure and excessive fill loading near the slope crest. Which combination of remedial measures is most defensible?

A Add unrestricted surcharge at the crest and deliberately increase water infiltration. B Remove all material at the slope toe without assessing the resulting stability. C Construct only a thin surface plaster layer and assume internal pore pressure will disappear. D Evaluate surface and subsurface drainage, suitable reduction or redistribution of driving loads, and engineered toe support or reinforcement where required.

Question 12 ప్రశ్న 12

A rock slope contains potentially detachable blocks bounded by persistent joints. A stabilization design proposes installing rock bolts. Which arrangement most directly improves the stability of the identified blocks?

A Install appropriately oriented bolts that cross potential release surfaces and develop adequate anchorage in more stable surrounding rock. B Place bolts entirely inside each loose block without crossing its release surfaces. C Choose bolt locations solely from rock colour without mapping joint orientation. D Assume rock bolts always eliminate the need for groundwater or overall slope-stability checks.

Question 13 ప్రశ్న 13

Geological investigation identifies evidence of geologically recent surface displacement along a fault crossing a proposed critical water-treatment facility. What hazard requires particular consideration beyond ordinary earthquake ground shaking?

A Chemical corrosion caused solely by the compass orientation of the fault. B A guarantee that the fault will remain inactive during the structure's design life. C Potential direct surface fault rupture and differential ground displacement across the facility footprint. D Only gradual consolidation settlement unrelated to geological deformation.

Question 14 ప్రశ్న 14

Two sites experience the same regional earthquake, but one is founded on stiff rock and the other on deep soft sediments. The soft-sediment site records stronger shaking over a frequency range relevant to its structures. Which explanation is most appropriate?

A The earthquake magnitude must be different at the two sites because local shaking differs. B Local soil and basin conditions can modify seismic-wave motion and amplify shaking at some frequencies, even during the same earthquake. C Soft sediments prevent seismic-wave propagation and guarantee zero acceleration. D Earthquake intensity and site response depend only on the distance between the two buildings.

Question 15 ప్రశ్న 15

A proposed pumping-station foundation lies on loose, saturated sand in an earthquake-prone area. Which statement correctly explains the basic liquefaction mechanism?

A Liquefaction occurs because all sand grains dissolve chemically during an earthquake. B Liquefaction requires every soil deposit to become completely dry during shaking. C Liquefaction occurs only in sound unfractured bedrock without pore spaces. D Strong cyclic loading may generate excess pore-water pressure in susceptible saturated soil, reducing effective stress and shear resistance.

Question 16 ప్రశ్న 16

An idealized saturated sand element has an initial vertical effective stress of 80 kPa. During undrained earthquake shaking, excess pore-water pressure rises by 60 kPa while total vertical stress is assumed constant. Using ru = excess pore-water pressure/initial effective stress, determine ru and the remaining vertical effective stress.

A ru = 0.75 and remaining effective stress = 20 kPa. B ru = 1.33 and remaining effective stress = 140 kPa. C ru = 0.25 and remaining effective stress = 60 kPa. D ru = 0.75 and remaining effective stress = 80 kPa.

Question 17 ప్రశ్న 17

After an earthquake, a riverbank founded on loose saturated sand shows lateral cracks and permanent horizontal ground displacement toward the river, although the original ground slope was gentle. Which mechanism is most likely?

A Uniform mineralogical weathering of all sand grains into quartz. B A dry rockfall from a vertical cliff. C Liquefaction-induced lateral spreading toward a free face. D A purely elastic deformation that leaves no permanent ground displacement.

Question 18 ప్రశ్న 18

A proposed reservoir pumping station is underlain by loose saturated sand with assessed liquefaction susceptibility. Which mitigation strategy is most defensible before final foundation design?

A Assume that a thick concrete floor slab alone prevents all pore-pressure buildup beneath the site. B Investigate appropriate soil densification, drainage or other ground-improvement measures and evaluate foundation performance under potential liquefaction-induced deformation. C Increase groundwater infiltration deliberately and omit seismic investigation. D Treat all potentially liquefiable soil as permanently stable because it carries static loads successfully.

Question 19 ప్రశ్న 19

A proposed underground water-storage structure lies over limestone containing solution cavities, with surface depressions and evidence of past sinkhole activity. Which geological hazard is most relevant?

A Rockburst caused solely by high compressive stress in deep crystalline rock. B Uniform swelling of unfractured quartz sand without moisture change. C A guarantee of high bearing resistance because limestone is a sedimentary rock. D Karst-related ground subsidence or localized collapse due to dissolution cavities and loss of supporting ground.

Question 20 ప్రశ్న 20

An urban area on thick alluvial deposits has experienced prolonged intensive groundwater abstraction. Monitoring shows groundwater-head decline and gradual regional land subsidence. Which explanation is most appropriate?

A Lower pore pressure can increase effective stress in compressible aquifer-system sediments and cause compaction and ground-surface lowering. B Groundwater extraction necessarily reduces effective stress and expands every clay layer. C Ground subsidence can occur only above limestone caverns and never in alluvial basins. D Restoring the original groundwater level always reverses every component of previous inelastic compaction.

Question 21 ప్రశ్న 21

Historical records indicate abandoned shallow underground mine workings beneath a proposed road alignment. What is the most appropriate engineering-geological response?

A Assume the ground is safe because mining stopped several decades ago. B Investigate the location and condition of voids, possible roof collapse and ground subsidence before selecting avoidance, ground treatment or structural measures. C Rely exclusively on the current road-surface appearance because underground voids cannot affect surface stability. D Assume the compressive strength of intact rock automatically establishes the stability of all old mine openings.

Question 22 ప్రశ్న 22

A municipality suspects gradual ground subsidence near a group of production wells. Which monitoring strategy is most appropriate for assessing the spatial extent and possible groundwater-related causes?

A Use only occasional visual inspection of building paint without recording ground elevations. B Determine subsidence from a single mineral-hardness measurement. C Combine repeated geodetic or InSAR displacement observations with groundwater-head monitoring and appropriate subsurface information. D Assume an InSAR displacement map alone always identifies the precise geological cause and time of future failure.

Question 23 ప్రశ్న 23

A road embankment in highly erodible soil is experiencing progressive gully erosion because runoff is concentrated at an unprotected drainage outlet. Which preventive measure is most appropriate?

A Direct additional uncontrolled runoff onto the exposed slope face. B Remove all vegetation and leave the eroded channel without protection. C Increase slope steepness without assessing runoff velocity or soil resistance. D Provide properly designed runoff collection and outlet protection, with appropriate erosion-control lining, vegetation or grade-control measures.

Question 24 ప్రశ్న 24

A monitored landslide shows 15 mm of downslope displacement over a 30-day observation interval. Assuming an average movement rate over this interval, what is the rate, and what conclusion can reasonably be drawn?

A 0.50 mm/day; the slope is moving, but the rate alone does not establish when or whether rapid failure will occur. B 2.0 mm/day; the slope is guaranteed to fail on the next day. C 30 mm/day; movement necessarily stops when monitoring begins. D 450 mm/day; the displacement proves the slope is permanently stable.

Question 25 ప్రశ్న 25

A major landslide in a narrow mountain valley temporarily blocks a river and forms an impounded lake upstream. Which additional geological-hazard consequence requires particular attention?

A The blockage guarantees that no flooding can occur downstream. B The temporary landslide dam permanently eliminates erosion throughout the valley. C Failure or overtopping of the landslide dam may produce rapid downstream flooding, so monitoring, hazard assessment and appropriate emergency measures are necessary. D The impounded water automatically strengthens the loose landslide debris and removes all instability.

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