Ground Penetrating Radar Survey of the Lithuanian Part of Medzhybizh Castle

Twelve kilometers of ground penetrating radar (GPR) data have been collected over the Brookswood aquifer in southwestern British Columbia. The data have been analyzed to assess how GPR can be used to characterize the distribution and connectivity of hydraulic units. We have used GPR to locate the aquifer/aquitard boundary at several locations in the study area. The electrical contrast between these two materials makes the aquifer/aquitard boundary an excellent target for GPR surveys. GPR was also used to reconstruct the paleo-environment of one area of the Brookswood aquifer. This was accomplished by using a modification of the concept of architectural element analysis. Radar elements were identified in the survey and were assigned sedimentary parameters using data from trenching and drilling in the area. These elements were used to develop an interpretation of the paleo-environment that provides information about the spatial distribution of hydraulic units. INTRODUCTION Hydrogeologists require quantitative data to produce a realistic model of the spatial variabilities in hydraulic properties of an aquifer. Such data can be difficult and expensive to obtain. A possible solution is to develop geophysical techniques as a means of aquifer characterization. Ground penetrating radar (GPR), a shallow geophysical technique, is well suited for this purpose as it can be used to image to a depth of up to 30m in sand and gravel environments. However, the image produced by a GPR survey does not supply hydrogeologic parameters directly. The focus of this paper is to investigate how GPR can be used for aquifer characterization. At an aquifer scale of lo’s to 100’s of meters, the most fundamental aspect of aquifer characterization is the determination of the aquifer’s hydraulic connectivity through mapping of aquifer/aquitard interfaces. GPR can be used for this purpose due to the large contrast in electrical conductivity between the sand and gravel material of an aquifer, and the clay rich material of an aquitard. The electrical conductivity of a material affects the penetration depth of radar waves, such that radar waves penetrate well through resistive material, but poorly through conductive material. Aquifers, composed of sands and gravels, are resistive, while aquitards, composed of clay rich materials, are electrically conductive. Therefore a radar survey will show good penetration in aquifer materials and very poor penetration in aquitards. By exploiting this difference in radar response, the aquifer boundaries can be mapped. At a smaller scale of centimeters to meters, the determination of the internal structure of an aquifer is also important for aquifer characterization. For example, anisotropy within the aquifer can cause significant differences in hydraulic properties and so must be identified where present. In addition, identification of sedimentary features aids in the determination of the paleo-environment that can provide important insight into the probable arcal extent and orientation of geological units. GPR can be used to image these features because of changes in their electrical properties. GPR and Sedimentology GPR has received considerable attention as a means of imaging sedimentary stratigraphy (Jo1 and Smith, 1992; Smith and Jol, 1992; Pratt and Miall, 1993; Greenhouse et al, 1987; Rea et al, 1991; Huggenberger et al, 1994). The key question that needs addressing is exactly which sedimentary aspects of the subsurface are imaged with GPR. A GPR survey, conducted by transmitting radar waves into the subsurface and recording the reflected energy, will image changes in the subsurface dielectric constant and conductivity. If these electrical properties correspond to changes in sedimentary parameters, then a GPR survey can be said to image sedimentary features. The dielectric constant and conductivity of earth materials are dependent upon composition and geometry of the solid and liquid components. Sedimentological classification is based upon five fundamental properties from which all others can be derived: grain composition, size, shapes, orientation and packing (Blatt et al, 1980). These five properties clearly are related to the composition and geometry of the solid component of a system. It is therefore reasonable to assume that a change in sedimentological properties at some boundary will cause a change in electrical properties. If the resulting change in electrical properties is large enough, then the sedimentary boundary will be imaged in a radar survey. The complicating issue is the liquid, usually water, component which does not play a role in sedimentary

Integrated geophysical investigation involving Ground Penetrating Radar (GPR) and Electrical Resistivity methods were carried out at Medina Estate, Lagos southwestern Nigeria to map the subsurface lithology in order to delineate its peat stratigraphy that has been causing foundation failure in the area. Twenty-one traverses (varying from 35-880 m in length) of Ground Penetrating Radar (GPR) survey were conducted along the streets of Medina trending NE-SW and NW-SE directions using the Mala 250 MHZ bi-static shielded antenna. Thirty-six Vertical Electrical Soundings (VES) were carried out using Schlumberger electrode array at some selected points along the established traverses within the area. The GPR data were processed into radar section using Rad Explorer software. The VES data were interpreted quantitatively using the partial curve matching method and 1-D forward modeling with Win Resist Software. Available litho-logs from boreholes drilled within the area were compared with the geophysical results. Results of the GPR survey delineated three geologic layers which include the topsoil with high amplitude, parallel to sub parallel, horizontal reflections, with thickness varying from 1 to 2 m across the entire profiles and composed of lateritic clay; peat layer with low amplitude, parallel sinuous/wavy reflections with depth of occurrence ranging from 2.0 to 8 m and clay with low amplitude, planar, horizontal, sub-parallel reflections underlying the peat layer. Vertical Electrical Sounding results revealed the presence of three geological layers which are the topsoil, peat and clay and sandy clay with layer resistivity values ranging from 20- 225 Ωm, 5 – 90 Ωm and 36 to 366 Ωm and thickness values ranging from 0.5 – 2 m, 4.0-29.0 m and infinity respectively. Borehole information confirms the occurrence of shallow peat with depth ranging from 1.5 to 9 m and clay layer with depth ranging from 9 to 21 m beneath the area. The GPR survey results correlates with the well logs acquired in the study area. Based on the correlation of the geophysical results with the well logs, the GPR gives better information about the peat layer compared to the Electrical ResistivityMethod. The information obtained from this study shows that the soils at shallow depth are organic soils which are difficult foundation materials because they exhibit very high compressibility, as such making shallow foundation impossible except some form of soil improvement is carried out. The alternative approach is the adoption of deep foundations in form of piles.
 Keywords: Foundation Failure, Geophysical Investigation, Ground Penetrating Radar, Vertical Electrical Sounding, Peat.

Identification of liquefaction and deformation features using ground penetrating radar in the New Madrid seismic zone, USA

Ground penetrating radar (GPR) surveys have been carried out at Schirmacher Oasis and Dakshin Gangotri located at Queen Maud Land, East Antarctica, during the 22nd Indian Antarctic Summer Expedition, 2002-2003. The present study confirmed the ability of the high-resolution GPR for monitoring the glaciers. It gives information about the health of the glaciers before it collapses. GPR survey over three frozen lakes near the Maitri Station provided the lakes' top ice thickness and bedrock depth. Similarly, the internal layers of the glaciers have been mapped in-situ using GPR. The results can be correlated with the results obtained by ice-core drill wells to understand the different field parameters (i.e., thickness of each layer, dielectric constant, etc.).

<p>Time-lapse ground penetrating radar (GPR) surveys in conjunction with automated single-ring infiltration experiments can be used for non-invasive monitoring of the spatial distribution of infiltrated water and for generating 3D representations of the wetted zone. In this study we developed and tested a protocol to quantify and visualize water distribution fluxes under unsaturated and saturated conditions into layered soils. We carried out a gridded GPR survey on a 0.3-m thick sandy clay loam layer underlain by a restrictive limestone layer at the Ottava experimental station of the University of Sassari (Sardinia, IT). We firstly established a survey grid (1 m × 1 m), consisting of six horizontal and six vertical parallel survey lines with 0.2 m intervals between them. The field survey then consisted of six steps, including <strong>i)</strong> a first GPR survey, <strong>ii)</strong> a tension infiltration experiment conducted within the grid and aimed at activating only the soil matrix, <strong>iii)</strong> a second GPR survey aimed at highlighting the amplitude fluctuations between repeated GPR radargrams of the first and second surveys, due to the infiltrated water moving within the matrix flow region, <strong>iv)</strong> a single-ring infiltration experiment of the Beerkan type carried out within the grid on the same infiltration surface using a solution of brilliant blue dye (E133) and aimed to activate the whole pore network, <strong>v)</strong> a third GPR survey aimed to highlight the amplitude fluctuations between repeated GPR radargrams of the first and third surveys, due to the infiltrated water moving within the whole pore network (both matrix and fast-flow regions), and <strong>vi)</strong> the excavation of the soil to expose the wetted region. The shapes of the 3D diagrams of the wetted zones facilitated the interpretation of the infiltrometer data, allowing us to resolve water infiltration into the layered system. Finally, we used the infiltrometer data in conjunction with the Beerkan estimation of soil transfer parameter (BEST) method to determine the following capacitive indicators of soil physical quality of the upper soil layer: air capacity <em>AC</em> (m<sup>3</sup> m<sup>–3</sup>), plant-available water capacity <em>PAWC</em> (m<sup>3</sup> m<sup>–3</sup>), relative field capacity <em>RFC</em> (–), and soil macroporosity <em>p<sub>MAC</sub></em> (m<sup>3</sup> m<sup>–3</sup>). Results showed that the investigated soil was characterized by high soil aeration and macroporosity (i.e., <em>AC</em> and <em>p<sub>MAC</sub></em>) along with low values for indicators associated with microporosity (i.e., <em>PAWC</em> and <em>RFC</em>). These findings suggest that the upper soil layer facilitates root proliferation and quickly drains excess water towards the underlying limestone layer, and, on the contrary, has limited ability to store and provide water to plant roots. In addition, the 3D diagram allowed the detection of non-uniform downward water movement through the restrictive limestone layer. The detected difference between the two layers in terms of hydraulic conductivity suggests that surface ponding and overland flow generation occurs via a saturation-excess mechanism. Indeed, percolating water may accumulate above the restrictive limestone layer and form a shallow perched water table that, in case of extreme rainfall events, could rise causing the complete saturation of the soil profile.</p>

In May of 1997, the Department of Geology and Geophysics at the University of Missouri-Rolla conducted a reflection seismic survey and a ground penetrating radar (GPR) survey for the Missouri Department of Transportation (MoDOT) along and adjacent to a 300 meter section of Interstate 44 in Springfield, Missouri. In October of 1997, a second GPR survey was conducted along the same section of interstate. The site was located approximately 1.5 kilometers west of Missouri Highway 266. The section of interstate studied overlies an active sinkhole and has experienced continued, localized subsidence. Seven 12-fold reflection seismic profiles were acquired along or near Interstate 44, using a Bison 24- channel seismograph and an EWG weight drop source. Forty-live GPR profiles were acquired along paved sections of Interstate 44 during the first survey. During the second GPR survey, the survey area was expanded to include a total of seventy ground penetrating radar profiles. A GSSI SIR-S GPR unit equipped with a 500 MHZ (megahertz) monostatic antenna/receiver was used to acquire the data. The geophysical surveys were successful. The reflection seismic data established that sinkholes, both active and nonactive are prevalent in the area. The seismic data also supports the interpretation that a sinkhole lies immediately beneath the interstate. The ground-penetrating radar data also proved to be of significant utility. Anomalous areas interpreted as voids on the GPR data were drilled and significant volumes of grout were injected. The second GPR survey established the success of the grouting program.

Improving the exploration of deep‐seated mineral deposits and assessing the stability of the mine pillars require that geophysical techniques are deployed in a fast and cost‐effective manner with minimal environmental impact. This research presents results from in‐mine reflection seismic experiments and a ground penetrating radar (GPR) survey conducted at the Maseve platinum mine, South Africa. The research aims to develop and implement methods to image platinum group metal (PGM) deposits and geological structures near mine tunnels and assess the stability of pillars. The seismic experiments were conducted using a sledgehammer source (10 lb), conventional cabled geophones (14 Hz), and a landstreamer with 4.5 Hz vertical component geophones. The GPR survey was conducted using a Noggin 500 GPR system with 500 MHz centre frequency. An image of the underlying orebody and geological structures down to 100 m from the mine tunnel floor (∼500 m below ground surface) was produced. We correlated the coherent reflections beneath the tunnel floor with a known Upper Group (UG2) PGM orebody. The final seismic section shows that the UG2 mineralisation is dissected by near‐vertical dykes, faults and fractures. These structures, faults in particular, are interpreted to have been active post‐mineralisation, implying that they may have contributed to the current complex geometry of the deposit. Four GPR profiles were collected around a stability pillar adjacent to the seismic lines. The radargram sections were processed to improve the signal‐to‐noise ratio (S/N). The results show different patterns of fracturing and stress‐induced structures. These fractures were shown to be sub‐vertical and, possibly, constitute complex micro‐structures within the pillar, which could compromise the pillar stability and integrity. The study demonstrates that in‐mine seismic and GPR surveys can be cost‐effective and valuable for mineral exploration.

<p>It is a truism that pavements deteriorate due to the combined effects of traffic loads and environmental conditions. The manner or ability of a road to meet the demands of traffic and the environment and to provide at least an acceptable level of performance to road users throughout its life is referred to as pavement performance. An important indicator of pavement performance is ride quality. This is a rather subjective measure of performance that depends on (i) the physical properties of the pavement surface, (ii) the mechanical properties of the vehicle, and (iii) the acceptance of the perceived ride quality by road users. Due to the subjectivity of ride quality assessment, many researchers have worked in the past to develop an objective indicator of pavement quality. The International Roughness Index (IRI) is considered a good indicator of pavement performance in terms of road roughness. It was developed to be linear, transferable, and stable over time and is based on the concept of a true longitudinal profile. Following the identification and quantification of ride quality by the IRI, pavement activities include the systematic collection of roughness data in the form of the IRI using advanced laser profilers, either to "accept" an as-built pavement or to monitor and evaluate the functional condition of an in-service pavement.</p><p>On the other hand, pavement performance can vary significantly due to variations in layer thickness, primarily due to the construction process and quality control methods used. Even if a uniform design thickness is specified for a road section, the actual thickness may vary. It is expected that the layer thickness will have some probability distribution, with the highest density being around the target thickness. Information on layer thickness is usually obtained from as-built records, from coring or from Ground Penetrating Radar (GPR) surveys. GPR is a powerful measurement system that provides pavement thickness estimates with excellent data coverage at travel speeds. It can significantly improve pavement structure estimates compared to data from as-built plans. In addition, GPR surveys are fast, cost effective, and non-destructive compared to coring.</p><p>The present research developed a sensing approach that extends the capability of GPR beyond its ability to estimate pavement thickness. Specifically, the approach links GPR thickness to IRI based on the principle that a GPR system and a laser profiler are independent sensors that can be combined to provide a more complete image of pavement performance. To this end, field data collected by a GPR system and a laser profiler along highway sections are analyzed to evaluate pavement performance and predict future condition. The results show that thickness variations are related to roughness levels and specify the deterioration of the pavement throughout its lifetime.</p>

On 4 September 2010, a MW 7.1 earthquake struck the Canterbury region of the South Island of New Zealand. Widespread liquefaction caused major damage to many structures, including the flood-control stopbanks along the lower reaches of the Waimakariri and Kaiapoi Rivers. Additional damage occurred during the subsequent MW 6.2–6.3 earthquakes of 22 February and 13 June 2011. Repeated LiDAR surveys indicated that up to 1 m of subsidence occurred in places. Visual inspections identified areas of significant damage, which have been repaired. However, internal damage to the stopbanks cannot be recognized by visual inspection. Thus electromagnetic (EM) and ground penetrating radar (GPR) surveys were undertaken.A pilot study was completed upstream of the confluence of the two rivers, along the northeast segment of the Waimakariri stopbanks and the southwest section of the Kaiapoi stopbanks. A complementary horizontal loop EM (HLEM) survey was carried out in advance of the GPR surveys. The HLEM measurements were done with the instrument oriented both parallel and perpendicular (transverse) to the stopbanks. Anomalous HLEM responses were noted at one location; subsequent GPR surveys indicated a change in the style of stopbank construction and repair, and possibly some internal cracking. HLEM readings were also taken at high and low tide levels along the tidally-influenced lower Kaiapoi River, and significant differences were observed. Finally, during the surveys, a surface crack was observed at one location, and a GPR line across that site suggested that the crack extended to depth.The results were complemented by velocity analyses using subsurface diffractions, and velocity variations were noted along the lengths of the stopbanks. The velocity changes appear to be broadly correlated with changes in the HLEM conductivity, which is not unexpected given the effects of water content and clay content on both the electrical conductivity and the GPR velocity.

Clayey subsurface strata in precipitation-driven wetlands act as aquitards that retain water and can affect wetland hydrology. If the aquitard layers have been cut through by drainage ditches, then restoring wetland hydrology to such sites may be more difficult because of the need to fill ditches completely with low hydraulic conductivity material. Ground penetrating radar (GPR) surveys were conducted to determine the depth and continuity of shallow clay layers and identify those that have been pierced by drainage ditches at Juniper Bay, a 300-ha drained Carolina bay in North Carolina, USA that will be restored. Carolina bays are a wetland type that occur as numerous, shallow, oval-shaped depressions along the Atlantic Coastal Plain. The GPR interpretations found that moderately fine-textured (clay loam, sandy clay loam, silty clay loam) and fine-textured (sandy clay, silty clay, clay) aquitards underlay coarser-textured horizons in most of the bay at an average depth of 1.6 m. Extensive ground truthing showed that, on average, GPR predicted the depth to these aquitards to within 16% of their actual depth. An atypical GPR reflection in the southeast sector of the bay was interpreted as a fluvial deposit without aquitards until a depth of 3 to 5 m. This area may require different restoration strategies than the rest of the bay. By comparing the depths of aquitards and drainage ditches, several areas were identified as likely locations of ditch-induced aquitard discontinuity that may require filling or lining of suspect ditches to prevent potential water losses if there are downward hydraulic gradients. Cost estimates by two professional firms indicated that GPR could provide large volumes of data with cost and time efficiency. GPR surveys are proposed as a useful tool for characterizing potential wetland restoration sites on the Atlantic Coastal Plain and other regions with similar soils.

Ground penetrating radar (GPR) surveys were conducted over the ancient Guanxingtai observatory in Dengfeng, Henan Province, China. Located in the Town of Gaocheng, 15 km southeast of Dengfeng City, Henan Province, the Guanxingtai Observatory is the earliest one of its kind so far extant in China, and is also one of the earliest buildings for astronomical observation in the world. It is a UNAVCO World Heritage Site, one of the Historic Monuments of Dengfeng in ‘the Center of Heaven and Earth’. In fact there is a building cluster around the Guanxingtai Observatory, built on a plot of 0.59 km2 and with a floor area of 657.41 square meters. GPR field campaigns were conducted in 2009 on the walls of the Guanxingtai Observatory with the 500-, and 900-MHz GSSI SIR-2 system. The GPR survey results show that the brick layers have dielectric constant ranging from 10.5–12, with a thickness of 0.57–0.6 m. There is possibly a refilled mortar layer behind the brick layer; strong diffractions are displayed in the radargrams for this layer.

Conventional ground penetrating radar (GPR) surveys detect subsurface inhomogeneities by the reflection of radio-waves. A short pulse of radio-frequency energy (several nanoseconds in duration) is transmitted into the ground and variations of the electromagnetic field are recorded. The GPR interpreter then attempts to identify echoes in this record which will provide an indication of the subsurface structure. It is commonly believed that the shape of the echo will be either an exact or inverted replica of the transmitted pulse. This will be true when the radio-waves are normally incident on plane, perfect (non-conducting) dielectric boundaries. However, geological materials are usually considerably conductive and when the transmit and receive antennas are separated, normally incident reflections are not recorded. Therefore, to interpret GPR data and to design optimum survey configurations, it is important to realise that the radar pulse shape can change on reflection and to understand how it changes .

In spite of the prevailing dry and windy climate conditions the mega dunes in the Badain Jaran Desert in northwestern China are relatively moist underneath a dry surface layer of less than 1 m. It is very common to find a salt lake directly at the foot of the leeward side of a mega dune. Using 50- and 100-MHz antennas we have conducted ground penetrating radar (GPR) surveys on both the windward and leeward sides of a couple of sand dunes in southeastern part of the Badain Jaran Desert. The GPR surveys clearly revealed the existence of numerous, quasi-evenly spaced bedding features on the windward side of the mega dunes, with a slope of orientation parallel to the slope of the leeward side of the dunes which closely coincides with the angle of repose of dry sands. The reason for the existing beddings is that on the leeward side sands on the dune surface can be cemented by moisture with periodic precipitation into layered beddings; and the caliches generated by these calcareous cement will be likely inducing more infiltrated water flow toward the leeward side and consequently channeling more local recharging water to the leeward side than to the windward side. The calcareous cement beddings performed as the ‘skeleton’ of the dunes and increased the mechanic strength of the sands and consequently facilitated the build-up of the high elevation mega dunes. This trend may be one of the key factors that help the existence of the lakes in a very arid environment with high evaporation rate. The GPR profile also clearly registered the water table beneath the sand dunes that gradually elevated toward the crest, implies that the desert lakes are recharged at least partly by the groundwater from local source. Numerically simulated radar profiles precisely reconstructed the observed profiles. It is a strong support to the rationality of the proposed internal structure of the dunes.

We studied the internal structure of snow by conducting a Ground Penetrating Radar (GPR) survey which has used for the study of the ground structure and the site in the past. First, the laboratory experiment was conducted to study variations in the radio wave's reflection patterns of the internal structure of snow at the Snow and Ice Research Center of NIED. Ice layers and water channels were created in an artificial snow block, and the reflections of radio waves under various conditions were analyzed. In the water channel, it was found that the formation of air spaces by the flow of water caused stronger reflection of radio waves, but when the flow of water increased and the air spaces were filled, radio waves weakened. Also, it could be confirmed the ice layer within the snow was appeared as the strong reflection. Next, GPR field survey was conducted to study the time-change of snow structure at the Murodo region in the Mt. Tateyama during the snowmelt season. In 2007, the internal structure of snow was surveyed over a wide range. From this survey, the changes in the internal structure of snow during the snowmelt season could be identified by the repeated investigations, and the distribution of the snow depth and the snowmelt process could be studied using two dimensional data. In 2008, GPR survey was conducted in the same area to acquire three-dimensional data, which enabled us to estimate the disappearance of ice layers and the route of water channels. These results show that the analysis data of GPR survey are appropriate for the assessment of the internal structure of snow.

Ground penetrating radar (GPR) surveys using a 500 MHz center-frequency antenna were used to image the developing fracture systems within the underground environment of the Waste Isolation Pilot Plant (WIPP), located near Carlsbad, New Mexico. The WIPP is a research and development facility designed to demonstrate the safe disposal of radioactive wastes generated at the United States Department of Energy facilities. The wastes will be stored 655 m (2,150 ft) below the land surface in the Salado Formation, a 610 m (2,000 ft) thick section of Permian evaporites. The 91 m (300 ft)-long waste storage rooms will close by failure thereby encapsulating the wastes. At lithostatic pressures, the salt undergoes ductile deformation, but near the free faces of the excavations the salt deforms in a brittle fashion. As a result, fractures develop in the floor and roof of the repository rooms and access drifts. The GPR surveys successfully imaged deformation caused by fracturing in portions of the roof and floor of the excavations. The results from the GPR surveys compare favorably with the available core log descriptions from boreholes. In the older, experimental portions of the WIPP excavations, roof fractures were imaged which extended diagonally from the sides of the rooms to approximately 2.1 m (seven feet) into the roof. GPR images of the floor show fractures that extend from the floor into a 0.9–1.5 m (three to five feet) thick anhydrite bed beneath the floor.