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ULTRA-HARD DEMOLITION CLASS B EXAM 2026-2027 BANK
QUESTIONS WITH DETAILED VERIFIED ANSWERS EXAM
QUESTIONS WILL COME FROM HERE (100% CORRECT
ANSWERS A+ GRADED
1. In the context of pre-demolition structural surveys, which method
provides the most accurate, quantitative data on concrete compressive
strength and internal void detection simultaneously?
A) Schmidt Rebound Hammer test
B) Ultrasonic Pulse Velocity (UPV) combined with core sampling
calibration
C) Ground Penetrating Radar (GPR) with a 1.6 GHz antenna
D) Ferroscan reinforcement mapping
Answer: B
Explanation: The Schmidt hammer only provides surface hardness,
which correlates loosely to compressive strength but cannot detect
voids. GPR is excellent for locating metallic and non-metallic inclusions
and delaminations but does not directly measure concrete strength.
Ferroscan maps rebar. UPV measures wave travel time, which is
affected by both the material's elastic modulus (strength) and internal
discontinuities (voids). When combined with destructive core sampling
to establish a specific strength-UPV correlation curve for that unique
,2|Page
concrete mix, it becomes the most quantitative and reliable method for
assessing both integrity and strength.
2. A sequential collapse analysis for a 12-story reinforced concrete
frame structure scheduled for explosive demolition indicates that the
pre-weakened columns on the ground floor have insufficient lateral
bracing from the intact floor diaphragms. What is the most critical
failure mode to address before loading explosives?
A) Buckling of pre-weakened columns under dead load only
B) Premature shear failure in the slab-column connection
C) Global lateral-torsional buckling of the entire structure due to wind
loads
D) Progressive crushing of the concrete in the pre-weakened zones
Answer: A
Explanation: Pre-weakening removes a significant portion of a column's
cross-section, drastically reducing its Euler buckling load. While dead
load may be static, the reduced section's moment of inertia is so low
that buckling under self-weight is the most immediate life-safety risk.
Pre-weakening designs must include a stability check confirming the
residual column section can safely support the full tributary dead load
with a factor of safety against buckling until the explosives are
detonated. Wind-induced lateral-torsional buckling is unlikely in such a
massive, redundant structure before the primary columns are severed.
3. During the demolition of a post-tensioned concrete bridge, the
tensioning end-anchorage is inadvertently cut with a diamond wire saw
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without prior de-tensioning. The stored elastic potential energy is
violently released. This phenomenon is best described as:
A) Creep rupture
B) Stress relaxation
C) Brittle fracture of the tendon
D) Sudden decompression of the bond stress
Answer: C
Explanation: The question describes a catastrophic energy release upon
sectioning a stressed tendon. Creep rupture is a time-dependent
material failure under sustained high stress, not a single cutting event.
Stress relaxation is a time-dependent loss of prestress in a fixed-length
tendon. There is no "decompression of bond stress" in unbonded or
bonded tendons that would cause this specific explosion-like energy
release. The correct term is brittle fracture, where the macroscopic
failure of the high-strength steel occurs with minimal plastic
deformation, releasing the enormous stored elastic strain energy
almost instantaneously, often causing the tendon to shoot out of the
duct with lethal force.
4. A rotary head drill rig used for rock splitting in a demolition quarry is
experiencing premature bit wear and asymmetrical button breakage.
Rotational speed and down-pressure are within manufacturer specs.
The most likely operational cause is:
A) Incorrect flushing medium viscosity
B) Misalignment of the drill string causing whipping in the hole
C) Excessive dissolved solids in the water injection
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D) Operating the hammer below its specified compressed air CFM
Answer: B
Explanation: Asymmetrical button breakage is a classic signature of
lateral forces and bending stresses on the bit, not pure axial
compressive loads. This indicates the bit is not rotating concentrically
with the borehole axis, causing it to strike the rock on an angle. This
misalignment, or "drill string whipping," creates high bending moments
at the bit face. Insufficient flushing air would cause overheating and
matrix abrasion, but not specific asymmetrical carbide breakage.
Excessive dissolved solids might clog waterways. Incorrect flushing
medium viscosity relates more to deep-hole drilling stability.
5. A masonry chimney is to be felled using the "dog-eared" notch
method. The hinge must be the last part to fail under the tension
induced by the chimney's rotation. To ensure this, the relative tensile
strength of the hinge must be calibrated against the:
A) Compressive strength of the bricks at the pivot point
B) Shear strength of the mortar bed joints at the notch apex
C) Tensile stress induced by the overturning moment, factoring in the
chimney's rotational inertia
D) Impact strength of the bricks upon ground contact to control
fragmentation
Answer: C
Explanation: The classic felling notch (dog-ear, rectangular, etc.) creates
a hinge of intact material. As the center of gravity rotates past the pivot
line, the chimney goes into free-fall rotation. The hinge experiences
tremendous tension on its outer fibers due to the overturning moment,
ULTRA-HARD DEMOLITION CLASS B EXAM 2026-2027 BANK
QUESTIONS WITH DETAILED VERIFIED ANSWERS EXAM
QUESTIONS WILL COME FROM HERE (100% CORRECT
ANSWERS A+ GRADED
1. In the context of pre-demolition structural surveys, which method
provides the most accurate, quantitative data on concrete compressive
strength and internal void detection simultaneously?
A) Schmidt Rebound Hammer test
B) Ultrasonic Pulse Velocity (UPV) combined with core sampling
calibration
C) Ground Penetrating Radar (GPR) with a 1.6 GHz antenna
D) Ferroscan reinforcement mapping
Answer: B
Explanation: The Schmidt hammer only provides surface hardness,
which correlates loosely to compressive strength but cannot detect
voids. GPR is excellent for locating metallic and non-metallic inclusions
and delaminations but does not directly measure concrete strength.
Ferroscan maps rebar. UPV measures wave travel time, which is
affected by both the material's elastic modulus (strength) and internal
discontinuities (voids). When combined with destructive core sampling
to establish a specific strength-UPV correlation curve for that unique
,2|Page
concrete mix, it becomes the most quantitative and reliable method for
assessing both integrity and strength.
2. A sequential collapse analysis for a 12-story reinforced concrete
frame structure scheduled for explosive demolition indicates that the
pre-weakened columns on the ground floor have insufficient lateral
bracing from the intact floor diaphragms. What is the most critical
failure mode to address before loading explosives?
A) Buckling of pre-weakened columns under dead load only
B) Premature shear failure in the slab-column connection
C) Global lateral-torsional buckling of the entire structure due to wind
loads
D) Progressive crushing of the concrete in the pre-weakened zones
Answer: A
Explanation: Pre-weakening removes a significant portion of a column's
cross-section, drastically reducing its Euler buckling load. While dead
load may be static, the reduced section's moment of inertia is so low
that buckling under self-weight is the most immediate life-safety risk.
Pre-weakening designs must include a stability check confirming the
residual column section can safely support the full tributary dead load
with a factor of safety against buckling until the explosives are
detonated. Wind-induced lateral-torsional buckling is unlikely in such a
massive, redundant structure before the primary columns are severed.
3. During the demolition of a post-tensioned concrete bridge, the
tensioning end-anchorage is inadvertently cut with a diamond wire saw
,3|Page
without prior de-tensioning. The stored elastic potential energy is
violently released. This phenomenon is best described as:
A) Creep rupture
B) Stress relaxation
C) Brittle fracture of the tendon
D) Sudden decompression of the bond stress
Answer: C
Explanation: The question describes a catastrophic energy release upon
sectioning a stressed tendon. Creep rupture is a time-dependent
material failure under sustained high stress, not a single cutting event.
Stress relaxation is a time-dependent loss of prestress in a fixed-length
tendon. There is no "decompression of bond stress" in unbonded or
bonded tendons that would cause this specific explosion-like energy
release. The correct term is brittle fracture, where the macroscopic
failure of the high-strength steel occurs with minimal plastic
deformation, releasing the enormous stored elastic strain energy
almost instantaneously, often causing the tendon to shoot out of the
duct with lethal force.
4. A rotary head drill rig used for rock splitting in a demolition quarry is
experiencing premature bit wear and asymmetrical button breakage.
Rotational speed and down-pressure are within manufacturer specs.
The most likely operational cause is:
A) Incorrect flushing medium viscosity
B) Misalignment of the drill string causing whipping in the hole
C) Excessive dissolved solids in the water injection
, 4|Page
D) Operating the hammer below its specified compressed air CFM
Answer: B
Explanation: Asymmetrical button breakage is a classic signature of
lateral forces and bending stresses on the bit, not pure axial
compressive loads. This indicates the bit is not rotating concentrically
with the borehole axis, causing it to strike the rock on an angle. This
misalignment, or "drill string whipping," creates high bending moments
at the bit face. Insufficient flushing air would cause overheating and
matrix abrasion, but not specific asymmetrical carbide breakage.
Excessive dissolved solids might clog waterways. Incorrect flushing
medium viscosity relates more to deep-hole drilling stability.
5. A masonry chimney is to be felled using the "dog-eared" notch
method. The hinge must be the last part to fail under the tension
induced by the chimney's rotation. To ensure this, the relative tensile
strength of the hinge must be calibrated against the:
A) Compressive strength of the bricks at the pivot point
B) Shear strength of the mortar bed joints at the notch apex
C) Tensile stress induced by the overturning moment, factoring in the
chimney's rotational inertia
D) Impact strength of the bricks upon ground contact to control
fragmentation
Answer: C
Explanation: The classic felling notch (dog-ear, rectangular, etc.) creates
a hinge of intact material. As the center of gravity rotates past the pivot
line, the chimney goes into free-fall rotation. The hinge experiences
tremendous tension on its outer fibers due to the overturning moment,
