CHINESE JOURNAL OF GEOPHYSICS Vol. 50, No. 5 Sep., 2007,,.., 2007, 50 (5) : Lu C M,Qin Z,Zhu H L, et al. Practical methods for de

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1 CHINESE JOURNAL OF GEOPHYSICS Vol 50, No 5 Sep, 2007,, 2007, 50 (5) : Lu C M,Qin Z,Zhu H L, et al Practical methods for detection of concealed cracks in highway pavement using ground penetration radar data Chinese J Geophys (in Chinese), 2007, 50 (5) : ,2, 1 1, , ,, ( GPR) (2007) P , Practical methods for detection of concealed cracks in highway pavement using ground penetration radar data LU Cheng2Ming 1,2,QIN Zhen 1,ZHU Hai2Long 1,3,LI Xiu2Zhong China University of Geosciences, Wuhan , China 2 Henan Lutong Geophysical Science and Technology Development Ltd, Zhengzhou , China 3 Institute of Geophysical Prospecting, SINOPEC Exploration & Production Research Institute, Nanjing , China Abstract This paper discusses the detection of concealed cracks under highway surface We described the ground penetrating radar method and the numerical and physical modeling results of the effects of vertical cracks on GPR wavefield in horizontally layered homogeneous media Comparisons show that the modeling results are in good agreement with those from project examination Both theoretical study and practice prove that detection of concealed cracks in highway structural layers with GPR is correct in theory and feasible in practice Keywords Ground Penetrating Radar ( GPR), Inspection, Highway structure layer, Concealed crack 1,,,1965 3,E2mail : com

5 : 1559,, r,, v, 1,2 1 81 [2 ], 6,, 2, 1,,, ( ) ; ( 1) 3 [3 ], 311 2, D h d 1 Fig 1 Principle of

2 5 : 1559,, r,, v, 1, [2 ], 6,, 2, 1,,, ( ) ; ( 1) 3 [3 ], 311 2, D h d 1 Fig 1 Principle of GPR [1 ], r = 1-2, v = c 1 + 2, 2 Fig 2 First break time curve of dispersion wave with same offset

1560 (Chinese J Geophys ) 50 x = - dπ2 t R, t R : t R = t 1 + t 2, t 1, t 2 2 d, (2) t 1 t 2 = 1 v = 1 v ( x + d) 2 + h 2, x 2 + h 2 (1) t 2 1 h v t 2 2 h v 2-2 - ( x + d) 2 h 2 = 1, x 2 h 2 = 1 [11

3 1560 (Chinese J Geophys ) 50 x = - dπ2 t R, t R : t R = t 1 + t 2, t 1, t 2 2 d, (2) t 1 t 2 = 1 v = 1 v ( x + d) 2 + h 2, x 2 + h 2 (1) t 2 1 h v t 2 2 h v ( x + d) 2 h 2 = 1, x 2 h 2 = 1 [11 [4 ] (2) ], (1) (2), t 1 + t 2 : t R = 1 v t 2 R 2 h v 2 - d h 2 (3) x 2 h 2 = 1 (4) (4) x = 0 t R = 2 hπv, (3) (3) (4) [ ] 3 ( ) ( ) (a) ; (b) Fig 3 Responses of GPR waves on thin lead model (a) Numerical simulation ; (b) Physical modeling 3, 4b, 312 ( : 112 m 4, ),, 40 cm 30 cm ;, 50 cm, [12 4a ] 5,

4 5 : ( 40 cm, 2 mm 30 cm) (a) (b) Fig 4 The result of (a) numerical modeling and (b) physical simulation on the vertical crack (length240 cm, width22 mm, depth of top230 cm),,,, 6 <50 mm 5 Fig 5 The wave field characteristic of vertical crack 50 cm 70 cm 120 cm 6b, 7 ( ) H h x t v, t = 1 v h 2 + x 2 + (2 H - h) 2 + x 2 (5) (1), x = 0 t 2 HΠv, h 313 H t 0,, ;

5 1562 (Chinese J Geophys ) 50 6 <50 mm (a) ; (b) Fig 6 Physical simulation result profile of GPR wave in response to a <50 mm steel tube in a two layer medium model (a) Raw data profile ; (b) Background eliminated profile 8 7 Fig 8 Diagram of the secondary dispersion wave radial route when singular dot is being in ultimate place Fig 7 Raypath of the secondary scattering wave starting from singular point and interface in a two layer model,, ; ( H) (0) 8, D, h = 0 ADCA C t = 1 v x + 4 H 2 + x 2-2 H 2 + x 2 (6) FB, CB = xπ2 ;, x = H, t HΠv x = H = B h = H 15 cm 4 ( ) ABA ABC AC + CB > AB, CD = AC, AD 15 cmπns t ns 900 = 2 BC, ADCA > ABA MHz 111 ns AD x, 0 ;

6 5 : 1563 x ; x = 0, t = 0,, t = 2 HΠv t 0 1, :,, 9 ( ), 9 Fig 9 Sections of numerical modeling in three layer medium model 4 1 cm 3 mm, [1,4,13 15 ] [16 23 ] 1 m 500 MHz m LTD MHz 30 cm 30 cm 14

1564 (Chinese J Geophys ) 50 cm, 20 cm, ( 10b) 11 L, 1 2 11 L Fig 11 Valid recording range relative positional relation between radar antenna and crack 10 cm, (a) ; (b) 3 6167 cm Fig 10 The diagram

7 1564 (Chinese J Geophys ) 50 cm, 20 cm, ( 10b) 11 L, L Fig 11 Valid recording range relative positional relation between radar antenna and crack 10 cm, (a) ; (b) cm Fig 10 The diagram of the positional relation between radar antenna and crack (a) Overlay ; (b) Departure,, 3 ( ) 500 MHz, 20 (20Π3) 5 cm,500 MHz 20 cm, 30 cm 5 cm, ( ) 6, 12 Fig 12 The profile of highway crack detected with GPR

5 : 1565 12 13a (, 15 ), 13 13a : ; 13b : 14 Fig 14

province 500 MHz 5 cm 13 16 (a) ; (b) (130 m ) Fig 13

5 14, 16 cm 34 cm ( ) 20 cm, 1 km 15 Fig 15 Crack

8 5 : a (, 15 ), 13 13a : ; 13b : 14 Fig 14 The diagram of a highway structure designed in Henan province 500 MHz 5 cm (a) ; (b) (130 m ) Fig 13 The characteristic of highway crack detected with GPR 5 14, 16 cm 34 cm ( ) 20 cm, 1 km 15 Fig 15 Crack pictures of a highway roadbed in Henan province, 1 km, 6,

9 1566 (Chinese J Geophys ) Fig 16 GPR testing profile on hidden crack in highway structure :,,, :,, ; ;,, :, ;, 18 : Fig 18 The meaning of crack top 17 Fig 17 The meaning of crack top depth,

10 5 : 1567, 7 (1) : 79 82, : Science Press, 2002, [ 6 ],, 1461 L, LΠ 3 ;, 1 m [12 ] ( References) [ 1 ] Institute (in Chinese), 1999, 22(1) : 41 45, Zhang S, Lu S M Reliability and necessity using GPR to detect highway surface thickness ( in Chinese ) Jiangsu Highway and Transportation Society [ 2 ] :,1994 Li D X Ground Penetrating Radar and Its Applications ( in Chinese) Beijing : Geological Publishing House, 1994 [ 3 ],2003, 27(1) : Yang T C, L S L, Wang Q R The application and development of GPR in detection of pavement thickness and highway structures Geophysical and Geochemical Exploration ( in Chinese), 2003, 27 [ 4 ] :,1996 Lu J M eds Principles of Seismic Prospecting ( in Chinese ) Dongying : University of Petroleum Press, 1996 [ 5 ] :, 2002 Wang B Z Computational Electromagnetism (in Chinese) Beijing :, 2002 : Ge D B, Yan Y B Electromagnetic Finite Difference Time Domain (in Chinese) Xi an : XiDian University Press, 2002 [ 7 ],2000,36 (3) :59 63 He B S, Zhang H X The suppression of numerical dispersion and improvement of absorbing boundary conditions in forward modeling of GPR Geology and Prospecting (in Chinese), 2000, 36 (3) : [ 8 ] Goldman Y, Hubans C, Nicoletis, et al A finite2element solution for the transient electromagnetic response of an arbitrary two2 dimension resistivity distribution Geophysics, 1986, 51(7) :1450 [ 9 ] Cangellaris A C Numerical stability and numerical dispersion of a compact 22DΠFDTD method used for the dispersion analysis of waveguids IEEE Microwave and Guided Wave Letters, 1993, 3 (1) : 3 5 [10 ] Taflove A, Umashankar K R Review of FD2TD numerical modeling of electromagnetic waves scattering and radar cross section Proceedings of the IEEE, 1989, 77 (5) : [11 ] [ ] :,2005 Li X Z Theoretical study of crack inspection with GPR wave and its application [ Ph D thesis] (in Chinese) Wuhan : China University of Geosciences, 2005 :,1998 Qi X M Theory of Electromagnetic Field (in Chinese) Wuhan : Wuhan University Press, 1998 [13 ],1999, 22 (1) :41 45 Deng J Z, Fang G X The application of ground penetrating radar to highway road surface inspection Journal of East China Geological [14 ],2004, (7) : Pan W Y, Xiang W J, Liu C H, et al Application of GPR in high2 class highway engineering Highway ( in Chinese), 2004, ( 7) : [15 ]

11 1568 (Chinese J Geophys ) 50,2000, 20(2) :30 32 Zhao H G, Song Y H The applications and practices of thickness test technology with exploring land radar on road Science and Technology of Henan Communication (in Chinese), 2000, 20 (2) : [16 ] Sun H X, Li F M Attenuation mechanism and application study of,2002, 30(5) : Zhu X A, Yuan S C Study on application of ground penetrating radar in road quality undamaged survey Coal Geology and Exploration (in Chinese), 2002, 30(5) : [17 ],2004, 1(3) : ,1996,20(2) : Niu Y X, Yuan S C, Wu J Z The application of geological radar to highway construction Chinese), 1996, 20(2) : Geophysical and Geochemical Exploration (in [18 ],2004, 1 (1) : 55 58,1996, 21(6) : Li D X Ground penetrating radar for test highway engineering Earth Science Journal of China University of Geosciences ( in Chinese), 1996, 21(6) : [19 ] 1999, 42 (6) : ,2003,21(1) :34 38 Zhao J S, Guo Y K, Tang P Y, et al The experimental researches of comprehensive damage2free subgrade quality inspecting technology Journal of Changsha Railway University ( in Chinese), 2003, 21 (1) : [20 ],2002, 21(3) : high impulse electromagnetic wave propagation of GPR Chinese Journal of Rock Mechanics and Engineering (in Chinese), 2002, 21 (3) : [21 ] Li C X, Qiang J K, Wang J J The application of ground penetrating radar of highway surface crack inspection Chinese Journal of Engineering Geophysics (in Chinese), 2004, 1 (3) : [22 ], Liu J P, Chen C, Xu S F Wave field character of vertical slit and its instance Chinese Journal of Engineering Geophysics (in Chinese), 2004, 1 (1) :55 58 [23 ],, Di Q Y, Wang M Y 2D finite element modeling for radar wave Chinese J Geophys (in Chinese), 1999, 42(6) : ( )

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