A new sampling layout and samples processing method was applied in the updating work of 1:250 000 regional geochemical data in Hami-Cihai iron deposit in Xinjiang. A number of anomalies of such elements as tungsten, molybdenum, zinc, gold, and silver were delineated and the detailed regional geochemical data were obtained. According to the regional geochemical survey, the metallogenic geological background was re-recognized based on the favorable metallogenic conditions. The authors have obtained some prospecting achievements, especially the discovery of Qingbaishan lead-zinc deposit in the Beishan metallogenic belt. The results obtained by the authors have broadened the exploration space of the Beishan metallogenic belt.

Ciying Formation in L Basin,which has the shallow layer,is characterized by shallow bury and complex geological origin.As the reservoir in Ciying Formation has high porosity and moderate permeability or high porosity and low permeability,it is a typical unconsolidated sandstone reservoir.With its rapid lateral variation and strong anisotropism,it's very difficult for elastic impedance and AVO techniques to make further distinction.In view of such a situation,the authors took advantage of prestack simultaneous inversion to make a prediction of shallow unconsolidated sandstone reservoirs.Based on seismic data,logging information and rock physics information,the authors applied prestack simultaneous inversion to finally get several elastic parameters such as P-impedence,S-imedence,and density.With these attribute parameters,the reservoirs can be easily and effectively predicted.

The result of conventional deterministic inversion cannot meet the need for identifying single sand body with high porosity because the lithological structure of the reservoir in 8^th Member of Shihezi Formation in Sulige gas field of Ordos Basin is very complex,the sandstone is thin,the porosity is low and the impedance of sandstone and mudstone is severely overlapped.In consideration of this situation and on the basis of an analysis of sensitivity reservoir parameters and key inversion parameters,the authors conducted the study of geostatistics inversion.Research shows that geostatistics inversion technology can effectively integrate geological,logging and 3D seismic data and greatly improve both vertical and lateral resolutions,thus effectively solving the problem of identifying single sand in thin alternating beds of sandstone and mudstone in the 8th Member of Shihezi Formation.In addition,the spatial arrangement of high-porosity sand body can be described correctly based on the statistical relation of P-wave impedance with porosity.The application effect is very inspiring.The application results show that the geo-statistics inversion method is a valuable method for fine reservoir description in the continental tight clastic lithological oil-gas reservoir and hence has an expansive application prospect.

The traditional geochemical exploration technique, which uses mainly trace element methods for geothermal systems and can delineate geothermal anomaly areas and search for concealed fault structures, is applied much more to the prospecting in geothermal systems of uplifting mountain type than that in geothermal systems of sedimentary basin type. The conditions of geothermal systems of sedimentary basin type, such as depth of hot water and good preservation which restricts the diffusion of the inorganic elements in geothermal water towards surface, lead to poor prediction effectiveness of geochemical exploration technique. In view of the fact that hot water in geothermal systems of sedimentary basin type is rich in the associated gas such as methane and carbon dioxide, and hence these gases are easy to micro-seep to surface and can be detected because of their strong penetrating power, the authors applied the soil gas method to the field trial to study the responding relationship between surface geochemical characteristics and the geothermal water enrichment area in the geothermal system of sedimentary basin type in Xiongxian County, Hebei Province.The results show that methane and hydrogen in soil gas are effective indicators to delineate the most favorable enrichment area in the geothermal systems of Xiongxian County, thus providing geochemical basis for geothermal systems exploration of similar types.

Gonghe-Guide basin and its alternate mountains have characteristics of large basin conduction type geothermal resources geothermal gradient, existence of granite in geothermal drilling basement at several places, and zonal distribution of basin edge mountain uplift-fracture-convection type hot springs with high water temperature. At present, there are controversies concerning heat mechanism. The authors query the argument of the mantle type heat source, and hold that the granite radioactive heat is the geochemical basis of the earth's crust internal heat source. In addition, the authors use geothermal drilling temperature measurement curve and geochemical geothermometer to predict geothermal reservoir temperature and depth. It is held that this is a meso-low temperature system. Finally, the geothermal gradient calculation problems and geothermal system are discussed.

The three-component magnetic survey in drill hole can improve the exploration accuracy of mineral body so as to direct the exploration drilling with the surface magnetic survey after detecting the anomalies near the drill hole better.The three-component magnetic survey in drill hole is also used in search for the blind orebody near or under the drill hole and in judging the shape,direction and depth of the mineral body.This paper mainly analyzes the magnetic field distribution characteristics of sphere and the laminated body,and summarizes the corresponding relationship between the characteristics of magnetic field distribution and orientations,such as location,direction of magnetization,and sloping direction.Also,the method of judging orebody direction is studied,and the spatial location of the orebody is determined.The three-component magnetic survey in drill hole is an effective method in search for the magnetic mineral body in the depth and detecting its occurrence situation.This method was applied to the ZK1102 drill hole magnetic data of an iron ore mine in Hainan,which improved the accuracy of determining the spatial location of an underground orebody.The results obtained by the authors provide a reference for drilling or reserves evaluation of magnetic orebody.

Through high-precision ground magnetic survey, high-precision aviation magnetic data application, and susceptibility measurements of drill core in Ili basin, the authors made a systematic study which included ferromagnetic mineral distribution characteristics, susceptibility variation characteristics of geochemical zoning of interlayer oxidation zone sandstone uranium deposits and the relationship with uranium mineralization, investigated feasibility, mechanism and methods of locating oxidation-reduction zone lby means of high-precision magnetic survey. The results obtained by the authors have an important role in prediction of front line of the oxidation zone and prognosis of uranium mineralization target.

Currently, increasing attention is paid to the green energy, and tourism has become a critical part of modern people's lives. In such a situation, geothermal exploration becomes more and more important in geophysical work because the targets of geothermal exploration are relatively deep, and their burial depths are about 1 km, or even up to 3 km or deeper. The single geophysical method is commonly employed and, as a result, the understanding of result is unclear, and the geological interpretation is not effective. In this study, the authors carried out a geothermal survey, in which the magnetic, CSAMT, TEM, MT/AMT (using EH-4 and V8 instruments) methods were employed. Multiple geophysical methods can supply multi-parameter information, and can cross-validate the effectiveness of each method. The successful selection of drilling targets demonstrated that the employment of integrated geophysical methods is an effective solution in challengeable exploration tasks.

The correct and effective delineation of synthetic geochemical anomaly is the key part of geochemical data processing, and plays a fundamental role in ore prospecting result. Traditional methods delineate synthetic geochemical anomaly based mainly on single element anomaly; nevertheless, many anomalies are caused by stratigraphic high background enrichment. In this paper, the authors use the method of Mahalanobis distance to identify geochemical outliers, and delineates synthetic geochemical anomaly. Because Mahalanobis distance is based on the theory of multivariate normal distribution, and hence is the direct promotion and application of multivariate statistical method. It fully considers three parameters, i.e., element mean content, variance and covariance, its computing process is directly based on samples, and therefore it is also the direct promotion of one-dimensional method having a unique anomaly identification function. The results of geochemical data processing applications with a variety of different scales and different sampling media show that the synthetic geochemical anomaly detected by Mahalanobis distance method has advantages of unique boundary, clear boundary, and reducing the effect of man-made anomaly delineation. In addition, with prominent anomaly intensity and single index, it can be used as an important parameter of anomaly evaluation with high probability of finding orebodies (mineralization). This method therefore can be promoted and applied in practice.

In Yanziyan target area of Jinping district in Yunnan Province, 1:25 000 soil survey led to the discovery of many element anomalies, including Pb, Zn, Ag, Cd, Hg, Sb, Cu, Cr. According to the ore-forming geological background of the survey area, the authors delineated the target area. By anomaly inspection, the authors found industrial-grade lead and zinc mineralization. Based on prognosis of target area's mineral reserves, the authors consider that the target area may be a medium to large lead-zinc deposit with considerable ore-prospecting potential.

The Dongshanwu area lies in northeastern Jiangnan orogenic belt, where stream anomalies of Au-As-Sb were delineated in 1989, and 2 603 soil samples were collected in 2011 for analysis of Au, Ag, Cu, Pb, Zn, As, Sb, Bi, W and Mo. According to mathematical geological analysis and single element anomaly evaluation, the authors hold that they belong to normal distribution except As. Au has a close affinity with As, Sb has a close affinity with Ag and Mo, and Ag and Mo have high background values. The concentration Clarke values and variation coefficients of Sb indicate that Sb were involved in mineralization. Drilling has already revealed Sb orebody, suggesting that the area has a good potential of Sb. Au anomalies are in accord with As anomalies, and Au is a concentrated element and has the biggest variation coefficient, suggesting that Au is unevenly distributed, Au mineral alteration is in accord with the tectonic belt, and Au is positively related to silicification. Through soil geochemical survey, 4 synthetic anomaly belts were delineated in Dongshanwu area, among which, Ⅰ,Ⅱ and Ⅳ have better prospecting potential. In addition, the authors detected that Sb and Au ores resulted from the superimposition of geological activities of different epochs.

The study area is located in Heishan area of Golmud in Qinghai Province. Its surface is covered with a large quantity of eolian sand and loess, and hence this area h is not suitable for soil and detritus sampling. An infilling 1:25 000 stream sediment survey method was used in early geochemical prospecting. The sampling density is 40 samples per square kilometers and the sampling grain size is -10-+40 mesh. Through analyzing the content, distribution and combination characteristics of elements, the authors hold that the contact zone between the intrusion and the first member of Tanjianshan Group in the study area has a good potential in search for polymetallic deposits. According to the above geochemical evidence, the authors delineated 5 comprehensive anomalies and subsequently evaluated them. Two ore-bearing skarn belts were found, which are confined in the range of AS4 synthetic anomaly. Two Cu-polymetallic orebodies were preliminarily determined in No. 1 ore-bearing skarn belt. The results show that the infilling 1:25 000 stream sediment survey method has favorable effects in ore prospecting at desertification mountainous plateau land surrounding the Qaidam Basin.

Based on the 1:50 000 stream sediment survey of an area of 1 450 km² in Huzhong-Tahe area, the authors collected 9 576 samples. Through the analysis of the samples in combination with the regional geological setting, the authors summarized geochemical parameters of 13 kinds of elements, the probability distribution of element values and the correlation of the elements. Sb, Pb, Ag, As, Zn, Cu, W, Mo, Bi, Cr and Ni are enriched in various degrees, so it is possible for them to form ore deposits. Combined Mo and Pb anomalies can be used as geochemical indicator for Mo. Based on the anomaly combination of stream sediment survey, the authors carried out 1:10 000 soil geochemical exploration and conducted surface uncovering, which led to the discovery of a molybdenum orebody, which is 1.4 m in width, with Mo grade of 0.014% in the concentration center. This proves that the method has good application value for ore prospecting in Huzhong-Tahe forest coverage area.

In view of the problem that the traditional calculation of surface nuclear magnetic resonance (SNMR) excitation field seldom considers various three-dimensional subsurface electric properties and different forms of launcher, the authors carried out surface NMR three-dimensional finite element modeling which premeditates the impact of a conductive medium. First, based on the three-dimensional finite element method, the authors realized the calculation of surface NMR excitation field under the condition of inhomogeneous medium. An approximate function was adopted to replace field source, so that it could be applied to different cases of transmitter loop. Then, the vertical component of excitation field was obtained through rotation matrix. Finally, the NMR response under different conditions was calculated. Several typical models were designed to analyze the effect of cap rock resistivity, formation resistivity, inhomogeneous medium and transmitter coil posture on SNMR signal. Numerical simulation shows that nuclear magnetic resonance is not sensitive to the change of the high cap rock resistivity. Low formation resistivity has great effect on SNMR response. The larger the inhomogeneous medium, the greater the SNMR response. For a certain size of the local inhomogeneous body, the difference between the SNMR response curves under the condition of low resistance is obvious. The coil posture should be considered in the field because it considerably impacts the NMR signal, and the coil orientation should be considered because the influence of the coil orientation on the magnetic signal is greater than electrical parameters.

The reduction to the pole as a magnetic anomaly data processing method has been widely used in the magnetic anomaly explanation.It is simple and convenient to estimate the buried depth of magnetic bodies by using northward moving distance of reduction to the pole magnetic anomaly maximum value.As for the long elliptical magnetic anomalies that extend not very long along the strike,the author determined the position of the comprehensive profile in accordance with northward moving distance of reduction to the pole.The magnetic anomaly maximum and actual geological conditions can eliminate or reduce the influence of oblique magnetization,and can achieve the goals because the anomaly of different exploration methods reflects the same geological body.

The Tidal Basin is a Mesozoic-Cenozoic stretching fault basin in central Alxa platform uplift on the northern side of the Hexi Corridor.In this basis,there are four uranium deposits belonging to sandstone type,mudstone type and coal rock type,thirteen uranium ore spots and dozens of uranium mineralized spots.Through an analysis of the verification results of airborne radioactive anomalies distributed in Pingyi depression of the Tidal Basin in combination with ore-forming geological setting,metallogenic characteristics,uranium source and ore-prospecting target bed of the basin,the authors investigated the vista in search for uranium deposits on the southern margin of Pingyi depression in the Tidal Basin.The analysis shows that Cretaceous strata in Pingyi area have favorable ore-prospecting target bed which seems to be the breakthrough point of ore-prospecting,and the airborne radioactive anomaly area is the key ore-prospecting segment deserving further investigation.

In this paper,through the analysis and study of the past aeromagnetic survey effect for kimberlite in Wafangdian of Liaoning Province and according to the basic requirements of kimberlite exploration,the authors put forward a means for selecting the key survey parameters with the purpose of improving the possibility of kimberlite exploration, and provide a reference for aeromagnetic survey of kimberlite deposits in the future.

Ground penetrating radar is an effective technology for detecting hydrates. Simulation test and study of the relationship between electromagnetic characteristics and gas hydrate saturation as well as other factors show that ground penetrating radar has great significance for permafrost hydrate exploration and reserve estimation in terrestrial area. Through production of samples by the laboratory the authors obtained a uniform natural quartz sand particle as a skeleton containing tetrahydrofuran hydrate and studied its dielectric constant. After the 1.5G high-frequency radar testing, it was found that the electromagnetic characteristics have obvious difference between the pure hydrate model and the THF hydrate model. When the saturation of the model of tetrahydrofuran hydrate is higher than 35%, the volume of hydrate increases, the dielectric constant of hydrate model increases too, and the radar speed decreases in the model. The THF hydrate does keep stability in nearly one hour at 10℃ room temperature and atmospheric pressure; when the hydrate and liquid tetrahydrofuran coexist in the pore of the model, the more the volume fraction of THF and the more liquid THF in the pore, the greater the dielectric constant of hydrate model is.

The observation of airborne electromagnetic (AEM) system not only includes the response of the underground media but also comprises various kinds of noise. The motion-induced noise is the main source of AEM system with the characteristics of lower frequency, higher amplitude and non-periodicity. The ensemble empirical mode decomposition (EEMD) method is an effective method for random signal decomposition which decomposes the signal into N-level intrinsic mode functions (IMF) components and residual component. The high level IMF component of low frequency is used to fit the motion-induced noise, and the noise-free signal can be obtained by reconstructing the remaining IMF component and the residual component. In this study, the authors used EEMD method to distinguish and suppress motion-induced noise for both the simulation data and the survey data, and compared the denoising result between the EEMD method and the traditional spline method. The comparison result shows that the EEMD method can remove the motion-induced noise effectively due to the high fitting ratio and thus can get higher signal-to-noise ratio.

Borehole TEM is a configuration in which the transmitter is on the ground and the receiver probe is in borehole. The receiver can be installed near the orebody through the borehole and hence can obtain more reliable information of the orebody. Borehole TEM is effective for conductive mineralization, particularly in areas where the capability of surface EM for defining a target is limited either by large depths or by interfering conductive bodies such as overburden shallow sulfides and peripheral mineralized horizons. Relative to the magnetic source, the detection depth of electric source borehole TEM is deeper and it is more suitable for deep prospecting in the complex terrain area. Through the study of the borehole TEM response characteristics of electrical source of borehole TEM, the authors aim to provide technical support for the application. Three component response characteristics of half space, 1D, 3D model were analyzed through forward modeling, and its validity for different models was proved in this paper. The results show that, due to the superimposition of the background field and anomaly field response upon transient response of total field, the curve shape is complex, and the electrical interfaces are only obviously reflected at the middle and late stage. The shape of the anomalous field curve is relatively simple, and the electrical interface is obvious; the anomaly of the horizontal component is on the whole higher than that of the vertical component. In this paper, by means of numerical simulation analysis, the authors obtained the preliminary understanding of electrical source of downhole TEM three component curve shape and verified the effectiveness of the electrical interface under the condition of the electrical emission sources. The results obtained by the authors can provide a reference for the further research.

3D resistivity inversion under the condition of undulate topography is a difficult problem in the current resistivity method. In order to solve this problem, the authors use a weighted regularized conjugate gradient method to accomplish three-dimensional resistivity inversion algorithm of undulating terrain. The method introduces weighted regularization thought which can significantly reduce the problem of the objective function iteration divergence and improve the stability of the inversion. A comparison of the two methods in eliminating topographic influence in the inversion shows that the direct use of the terrain resistivity method of 3D inversion can yield better resolution, which can effectively eliminate the error caused by terrain. Nevertheless, under the condition that the rolling angle is almost vertical such as the cases of rivers and dams. The continual utilization of this method can hardly get a satisfactory result because it causes the inverse divergence. In such cases, the use of topographic correction method has some advantageous effects.

Under the layer tuning effects,the interference patterns are changing with different offsets of seismic reflections and,as a result,the amplitude and frequency information is distorted,and this will worsen the confidence and resolution of the AVO/AVA analysis and inversion.Firstly,the authors gave the seismic reflection equations with tuning effects,with the modeling examples illustrating characteristics of the tuned seismic gather.Secondly,in consideration of the different detuning levels caused by the changing layer-thickness,the authors constructed the self-adaptive non-stationary decomposition via local Lamoureux time window.Finally,the authors built the non-stationary cost function for matching seismic angle gather to correct the amplitude and waveform stretch.Field application demonstrates the feasibility of the proposed method in improving the quality of seismic data with larger angle,with the high-quality data causing the success of reservoir prediction and hydrocarbon identification.

The full waveform inversion method can be regarded as a large nonlinear minimization problem.In this method,Hessian operator exerts significant influence on the inversion result.Nevertheless,traditional optimization methods can only express the Hessian operator approximately,which will lead to low inversion accuracy,slow convergence speed,and the result that the parameter cannot be focused,especially for deep inversion region target with poor illumination.In contrast,the truncated Newton method,a new optimization method,can obtain the information of Hessian operator more accurately by the computation of the product of Hessian matrix and a known vector,and thus can solve the problem mentioned above.Therefore,this paper achieves full waveform inversion in the frequency domain based on truncated Newton method.And the model test shows that the truncated Newton method has more precise inversion results and improves the efficiency of inversion,especially for deep area with insufficient illumination compared with the limited memory BFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno,L-BFGS) method.

In this paper,the authors studied velocity and attenuation anisotropy characteristics of turbidite thin interbed saturated with fluid,and analyzed the main influence factors such as group angle,net-to-gross,saturation and porosity.The results show that there are differences in condition between low frequency and high frequency.Through the anisotropy velocity analysis,the authors detected that compressional wave velocity increases with the increase of saturation and angle,and compressional wave velocity decreases with the increase of the net to gross.Through the attenuation anisotropy analysis,it's known that compressional wave attenuation parallel to the bedding is less than the result perpendicular to the bedding plane.Attenuation depends on the medium heterogeneity,and when medium inhomogeneity is maximum,attenuation is the largest.

The attenuation and dispersion of seismic wave will occur when seismic wave propagates in patchy-saturated media and is influenced by fluid patch distribution and size.The patch characteristics in turn can be influenced by capillary forces mainly.The effect of capillarity on wave attenuation in patchy-saturated rocks is not fully understood.In view of such a situation,the authors make use of the concept of patch membrane stiffness as a macroscopic expression of capillarity,incorporate the capillary forces into spherical patchy saturation model by changing a pressure discontinuity at patch interfaces,get a new model and compare the variation of wave attenuation and dispersion before and after the consideration of the capillarity based on the new model.It is suggested that considering capillarity will increase seismic velocity and decrease the dispersion and attenuation coefficient.The authors applied this capillary-extended spherical patchy saturation model to interpret velocity-saturation and attenuation-saturation relations.A comparison with the original model shows that the new model can fit the velocity-saturation and attenuation-saturation experimental relation trend well,which suggests that capillary-extended spherical patchy saturation model can have important implications for interpreting velocity-saturation and attenuation-saturation relations in patchy-saturated rocks.

Micro-seismic monitoring technology is an important means to evaluate the fracturing effect of low permeability reservoir and to guide the development of fine water injection in oil reservoir.Through the observation and analysis of micro-seismic events produced by fracturing,the location,size,flow conductivity,geometric shape and local fracture distribution regularity of fractures can be obtained.Wangpanshan Chang 8 reservoir of the Jiyuan oilfield is characterized by low porosity,low permeability and low voltage,and hence production will decrease soon after the conventional fracturing production is conducted for a period.In recent years researchers have carried out mixed water volume fracturing and implemented the micro-seismic monitoring.The monitoring of Lu 58-54 well mixed water volume fracturing results shows that the long slit produced is up to 315.97 m,the seam width is 104 m,the fracture height is about 58 m,the affected volume is about 24.48 million m³,and the direction is NE 19.5·.The fracturing has caused the reservoir layer cracks to open and drainage radius to increase,thus increasing the amount of single well production.The effect is very obvious,and the results obtained by the authors lay a solid foundation for further fine development of the reservoir.

Prestack time migration can realize the fine imaging of geological structure and also provide a high resolution imaging section for lithological reservoir prediction.In order to apply the prestack time migration technology effectively to the coal seismic data processing,the authors,on the basis of the characteristics of coalfield seismic data,studied a series of prestack processing technologies,introduced the tomographic inversion method by using first arrival wave and reflected wave to establish fine migration velocity field,and built prestack time migration work flows and process measures which could be used to actual data.The actual data imaging results show that,compared with poststack migration method,the prestack time migration imaging result has greatly improved the imaging precision and amplitude preservation,which is helpful to the fine structure interpretation and lithological inversion of coalfield seismic data.

Built in 1959, the Zhenjiang Jianbi Power Plant is one of the main power plants in the power grid of East China. Its total power generation has hit over 100 billion kWh in the past twenty-six years. Nevertheless, a significant amount of coal ash has also been generated. To investigate the environmental effects of coal ash, the authors selected Longshan Ash Mountain and Zhenguan Ash Mountain as the study objects. Testing the samples of coal ash, surface water and its surrounding sediments, rocks, soil, and rice seed around the coal ash mountain areas, the authors have found that the topsoil in the study area is rich in selenium (Se) due to the influence of coal ash. According to the classification criteria set by Tan Jianan, 32.96% of the soil contains a medium level of Se, 43.08% is rich in Se, 7.86% is low in Se concentration, 6.76% is very low in Se concentration, and 9.34% contains excessive Se. The soil with excessive Se is mainly located around the downstream coal ash area, with a maximum amount of 14.7×10^-6. It is found that the richness of Se in the farmland far away from coal ash areas mainly stems from high Se concentration in the irrigation water, while the richness of Se in the farmland close to coal ash areas is attributed not only to irrigation but also to the sediments of coal ash brought by the water flow. The dendrogram analysis of Se and heavy metals shows that the region affected by Se is also affected by Cd, Hg and Pb. The richness of these heavy metals is ranked as Hg > Cd > Pb. The topsoil is generally not contaminated by As, Cd, Cr, Cu, Hg, Hi, Pb, Zn and other heavy metals because the concentration of these heavy metals is less than the natural amount. Only the concentration of Cd and Hg is close to the maximum of the second degree in the national farmland standard. Affected by soil environment, the study area has Se-rich rice, whose concentration of As, Cd, Cr, Hg, Pb and other heavy metals does not exceed the food contamination standard. Based on these findings, the authors suggest using different irrigation sources in the study area. Specifically, we should use Se-rich water to irrigate the Se-insufficient soil so as to expand the area with Se-rich soil, and use the average water to irrigate the Se-excessive soil so as to reduce Se concentration. The results of the study also imply that coal ash is rich in Se and contains very little harmful heavy metals. Therefore, it may be profitable to extract Se from coal ash and produce Se-rich fertilizers.

Due to the long-term geological process and external factors, the bridge foundation as a key component of bridge always tends to get some diseases. Considering that the traditional common-offset method cannot detect bridge foundation defect very well, this paper proposes the use of a special common-source method to detect the bridge foundation defect. The forward modeling of the bridge foundation detection is realized by GprMax. The differences can be found easily by comparing the result of normal bridge foundation and that of defective bridge foundation. The result obtained by the authors is helpful to identifying the defective bridge foundation, which proves that GPR is an effective method for detecting the defect of bridge foundation.