5B-2-1
CRACK SITUATION GRASP OF DIGITAL IMAGE METHOD
Tatuhide NAKANE, Hisasi TAKAGI, Masaharu OZAWA
Kokusai Kogyo Co., LTD.
JAPAN
mo31208@kkc.co.jp
KEY WORDS: Crack, Laser, Optical detection sensor
ABSTRACT
Among a variety of damage phenomena that the pavement road shows, the crack of the road is the most remarkable. The influence that
the crack exerts on the durability of the pavement road is extremely large. It is necessary to understand the damage situation of the crack
in the maintenance control of the pavement road.
The device that records the road image to understand the damage situation of the crack is developed. The record device is divided into an
analog method and a digital method. Both can be installed in the vehicle and the road image is recorded at a speed of 80km per hour. A
digital method scans the state of the road with a laser spot and an optical detection sensor. The laser spot rotates in the direction where
the road is crossed at high speed and catches the change in an individual point in the reflection light amount with the optical detection
sensor. Information caught with the optical detection sensor is recorded in the W-VHS videotape. When there is no crack in the road and
the road is excellent, the reflection light amount increases and is recorded as information on a bright point. The crack exists in the road,
and when the laser spot scans the crack, the reflection light amount decreases and is recorded as information on a dark point. The crack is
recorded as if the shadow and can confirm the existence of the crack as a result.
1 INTRODUCTION
In the road extension of Japan, there are about 1,150,000km and
75% is a pavement road (1998). Cost by which the road is
maintaining controlled increases every year as the road extension
increases. It is necessary to distribute the limited maintenance
budget efficiently so that the country and the municipality may
offer a safe, pleasant road service. Therefore, it is important that
the road manager understands the damage situation on the surface
of the pavement road to do an effective investment and reflect the
result in the road mending.
2 GRASP OF PAVEMENT DAMAGE
The damage situation of the road is expressed by the crack, the rut,
and roughness in Japan. To evaluate the use of the pavement
quantitatively, Ministry of Construction developed maintenance
control index (MCI) as an integrated evaluation value of three
elements. Especially, the influence of the crack on the durability
of the pavement road is extremely large. The road manager is
confirming the crack situation by various means. 20 years or more
ago was only a method of confirming the existence of the crack by
eyes. This method takes time to understand the damage situation
of a wide-ranging road and needs a large labor. Moreover, it is
dangerous to confirm the crack on the crowded road. It is general
to use the automatic measurement vehicle where a special record
device was installed when the pavement damage of a wide-
ranging road is understood now. As a result, a prompt,
economical, safe pavement damage can be understood.
3 AUTOMATIC MEASUREMENT DEVICE
There are about 10 vehicles to investigate the damage situation of
the pavement road in Japan. The system that automatically
investigates the damage situation is installed in the vehicle. The
item which this vehicle investigates is a crack, a rut, and
roughness. The car equipped with the investigation system can
run about 80km or less and acquire the damage situation of the
road. Naturally, there is a big difference at the speed of the
investigation when it is compared to execute the investigation as
man walks and to execute the investigation by using the car. Most
cars (system) cannot investigate in daytime and are executing the
investigation at nighttime because the measurement technique is
influenced by the sunlight. All cars are used to investigate an
expressway and a general road.
Figure 1- Road Damage Investigation Car
