Question 1
______ deflection is obtained as the sum of mean rebound deflection and standard deviation.
A. Specific
B. Characteristic
C. Mechanistic
D. Definite
View Answer
Answer: Option B
Explanation:
Characteristic rebound deflection is used to represent the sum of mean rebound deflection and the standard deviation. The value of standard deviation taken varies with respect to the traffic conditions. For the traffic < 1500 CVPD indicating minor road, one times standard deviation is taken and for > 1500 CVPD indicating major roads, two times the standard deviation is taken.
Question 2
A loaded truck with a rear axle load of ______ is used for the deflection study.
A. 4880 kg
B. 8770 kg
C. 4085 kg
D. 8170 kg
View Answer
Answer: Option D
Explanation:
The equipments required for the test are the Benkelman beam, loaded truck, accessories like tyre pressure gauge, measuring tape, thermometer, etc. the loaded truck has the rear axle with weight 8170 kg. The design wheel load is a dual wheel load assembly with a gross weight of 4088 kg.
Question 3
BBD studies were carried out on a highway pavement at a temperature of 40°C. The rebound deflection was found to be 1.41 mm. what would be the corrected rebound deflection?
A. 1.33 mm
B. 1.35 mm
C. 1.40 mm
D. 1.36 mm
View Answer
Answer: Option D
Explanation:
The correction for temperature is to be applied, as in the question the test temperature is 40°C, but the standard is 35°C. So, the correction to be applied is negative and it is taken as 0.01 per degree.Corrected Dc=Dc+(Standard temperature-field temperature)×0.01Corrected Dc=1.41+(35-40)×0.01=1.36 mm
Question 4
Before starting the test, the pavement stretch is divided into fair, good and poor based on ______
A. General condition of the pavement
B. Ability to carry wheel load
C. Number of cracks
D. Existing deflections due to loading
View Answer
Answer: Option A
Explanation:
Before starting the test, it is necessary to divide the pavement stretch into groups namely fair, good and poor. This is done based on the general condition of the pavement. This includes a general survey of ruts, cracks, and undulations on the pavement surface.
Question 5
Benkelman beam deflection test is a type of ______
A. Destructive testing for flexible pavement
B. Non-destructive testing for flexible pavement
C. Destructive testing for rigid pavement
D. Non-destructive testing for rigid pavement
View Answer
Answer: Option B
Explanation:
BBD test is a non-destructive test that is used for the structural evaluation of the flexible pavement. It measures deflection using a deflectometer present in the equipment and it is not destructive in nature. Deflection is an important feature that gives an idea about the condition of flexible pavements.
Question 6
e. A, B and C respectively if least count of dial gauge is 0.01 mm and the value of k is 2.91.
A. 0.28 mm, 0.63 mm and 1.96 mm
B. 0.82 mm, 0.36 mm and 1.69 mm
C. 1.82 mm, 1.36 mm and 0.69 mm
D. 1.28 mm, 1.63 mm and 0.96 mm
View Answer
Answer: Option D
Explanation:
Before starting the calculations, it is necessary to check for leg correction.Point A:Di-Df=48-45=3 div≈0.03 mmSince Di-Df>0.025 mm, leg correction needs to be applied and rebound deflection can be found using D=0.02(Do-Df )+0.02k(Di-Df ) mm. The value of D0 is 0 and it is to be taken as 100.D=0.02(100-45)+0.02×2.91(48-45)=1.28 mmPoint B:Di-Df=34-30=4 div≈0.04 mmSince Di-Df>0.025 mm, leg correction needs to be applied and rebound deflection can be found using D=0.02(Do-Df )+0.02k(Di-Df ) mm. The value of D0 is 0 and it is to be taken as 100.D=0.02(100-30)+0.02×2.91(34-30)=1.63 mmPoint C:Di-Df=59-57=2 div≈0.02 mmSince Di-Df<0.025 mm, there is no need to apply the leg correction and rebound deflection can be found using D=0.02(Do-Df ) mm. The value of D0 is 5 and it is to be taken as 105.D=0.02(105-57)=0.96 mm
Question 7
Find the standard deviation for a highway with heavy traffic if the rebound deflection values obtained at 10 points are 1.4, 1.33, 1.36, 1.44, 1.58, 1.62, 1.60, 1.55, 1.47 and 1.38.
A. 0.01
B. 0.11
C. 1.11
D. 1.01
View Answer
Question 8
It is not necessary to apply a correction for temperature if the testing temperature is lower than 35°C.
A. True
B. False
View Answer
Answer: Option B
Explanation:
It is necessary to apply corrections for testing temperatures both lower and higher than 35°C. if the testing temperature is lower, the correction is positive and if it is higher, the correction to be applied is negative.
Question 9
The Benkelman beam deflection test involves finding the ______ of the pavement.
A. Recurring deflection
B. Deflection
C. Rebound deflection
D. Bound deflection
View Answer
Answer: Option C
Explanation:
The Benkelman beam deflection test finds the rebound deflection of the pavement layers under a standard wheel load and tyre pressure. When the pavement is subjected to moving wheel load, it deflects under that. When the surface comes back to its original state, rebound deflection happens.
Question 10
The test started from an initial point is stopped after ______ for intermediate deflection measurement.
A. 3 m
B. 2.7 m
C. 8.7 m
D. 9 m
View Answer
Answer: Option B
Explanation:
The Benkelman beam is placed at the first point and the initial deflection is measured. Then it is moved 2.7 m from that point to measure the intermediate deflection. Another 9 m from the second point, the final deflection measurement is taken.
Question 11
The testing is to be carried out during the ______ season.
A. Monsoon
B. Winter
C. Summer
D. Autumn
View Answer
Answer: Option A
Explanation:
The deflection studies should be carried out during the worst possible condition of the pavement. The monsoon season is when this can be achieved. If carried out at other times, then the correction for moisture has to be done.
Question 12
What is the equation to find the rebound deflection if the relationship between intermediate deflection reading Di and the final deflection reading Df is Di-Df<0.025 mm?
A. D=0.02(Do-Df)+0.02k(Di-Df)mm
B. D=0.02(Do-Df)+0.02k(Di-Df)cm
C. D=0.02(Do-Df)mm
D. D=0.02(Do-Df)cm
View Answer
Answer: Option C
Explanation:
The equation to find rebound deflection when Di-Df<0.025 mm is given as D=0.02(Do-Df) mm. D=0.02(Do-Df)+0.02k(Di-Df) mm is the equation used when Di-Df>0.025 mm. Do is the initial deflection reading.
Question 13
What is the length of the slender beam portion of the Benkelman beam?
A. 3.66 m
B. 2.44 m
C. 3.33 m
D. 2.22 m
View Answer
Answer: Option A
Explanation:
The Benkelman beam consists of a slender beam of length 3.66 m. There is a pivot on the beam at a distance of 2.44 m from the measurement probe end. This assembly is on a datum frame and there are legs to support the same.
Question 14
What is the operating speed of Benkelman beam deflection equipment?
A. 50 km/hr
B. 32 km/hr
C. Crawling
D. Pulsating
View Answer
Answer: Option C
Explanation:
the operating speed of Benkelman beam deflection equipment is very slow and it can be considered to be crawling speed. The automatic road analyser is the equipment that moves with operating speed between 30 and 100 km/hr. Instrumented car is the equipment that operates at a speed of 32 km/hr.
Question 15
What is the standard temperature taken for the rebound deflection calculation?
A. 27°C
B. 30°C
C. 35°C
D. 25°C
View Answer
Answer: Option C
Explanation:
The temperature during the Benkelman beam deflection testing is to be noted. If it is not carried out at the standard temperature of 35°C, a correction for the same is to be provided. If the temperature is higher, the bituminous surface would be soft and deflect more.
Question 16
What would be the corrected rebound deflection if the rebound deflection obtained from BBD studies is 1.33 mm? The test was conducted at 35°C on sandy soil with 5% moisture content. The annual rainfall of the area is obtained as 1050 mm.
A. 1.50 mm
B. 1.56 mm
C. 1.48 mm
D. 1.46 mm
View Answer
Answer: Option B
Explanation:
There is no need to apply temperature correction because the test has been carried out at standard temperature. The correction for moisture content has to be done by referring to the graphs provided in IRC 81:1997. The code can be accessed from the below link:https://archive.orgThe graph labelled as the code can be used for sandy soils with annual rainfall < 1300 mm. From the graph, the correction factor is obtained as 1.17.Corrected Dc=Dc×correction factorCorrected Dc=1.33×1.17=1.56 mm
Question 17
What would be the corrected rebound deflection if the rebound deflection obtained from BBD studies is 1.38 mm? The test was conducted at 30°C on a clayey soil having a plasticity of 10% and a moisture content of 4.5%. The annual rainfall of the area is obtained as 1450 mm.
A. 2.57 mm
B. 1.57 mm
C. 2.75 mm
D. 1.75 mm
View Answer
Answer: Option A
Explanation:
The temperature correction needs to be applied first and then the moisture correction on the temperature corrected value.Corrected Dc=Dc+(Standard temperature-field temperature)×0.01Corrected Dc=1.38+(35-30)×0.01=1.43 mmThe correction for moisture content has to be done by referring to the graphs provided in IRC 81:1997. The code can be accessed from the below link:https://archive.orgThe graph labelled as in the code can be used for clayey soils with PI < 15% and annual rainfall > 1300 mm. From the graph, the correction factor is obtained as 1.8.Corrected Dc=Dc×correction factorCorrected Dc=1.43×1.8=2.57 mm
Question 18
When Di-Df>0.025 mm ______ correction is applied to the equation for computing rebound deflection.
A. Leg
B. Moisture
C. Skid
D. Temperature
View Answer
Answer: Option A
Explanation:
The equation to find rebound deflection is D=0.02(Do-Df) mm. This is applicable when Di-Df<0.025 mm and when Di-Df>0.025 mm, there is a need to modify the equation by introducing terms for leg correction. The equation hence becomes D=0.02(Do-Df)+0.02k(Di-Df) mm.
Question 19
Which IRC code is referred to while performing the BBD studies?
A. IRC 91:1887
B. IRC 81:1887
C. IRC 91:1997
D. IRC 81:1997
View Answer
Answer: Option D
Explanation:
IRC 81:1997 is used to refer to while conducting the BBD test. It gives the guidelines for the strengthening of flexible road pavements using the BBD studies. The BBD studies can be used to design overlay for the rehabilitation of pavements.
Question 20
Who developed the Benkelman beam deflection studies (BBD) and in which year?
A. A.C Benkelman in 1935
B. C.A Benkelman in 1935
C. A.C Benkelman in 1953
D. C.A Benkelman in 1953
View Answer
Answer: Option C
Explanation:
It was A.C Benkelman who devised the Benkelman beam deflection studies in the year 1953. It was during the AASHO (now AASHTO) road test for the purpose of measuring the deflection of the pavement layers.