scholarly journals Geophysical investigation to assess condition of grouted scour hole : Old River Control Complex—Low Sill Concordia Parish, Louisiana

2021 ◽  
Author(s):  
Janet Simms ◽  
Benjamin Breland ◽  
William Doll
Keyword(s):  
Seismic Refraction ◽  
Low Frequency ◽  
Borehole Data ◽  
Geophysical Investigation ◽  
Seismic Surveys ◽  
Geophysical Surveys ◽  
River Control ◽  
Ground Penetrating ◽  
Control Complex ◽  
Water Borne

Geophysical surveys, both land-based and water-borne, were conducted at the Old River Control Complex‒Low Sill, Concordia Parish, LA. The purpose of the surveys was to assess the condition of the grout within the scour region resulting from the 1973 flood event, including identification of potential voids within the grout. Information from the ground studies will also be used for calibration of subsequent marine geophysical data and used in stability analysis studies. The water-borne survey consisted of towed low frequency (16-80 MHz) ground penetrating radar (GPR), whereas the land-based surveys used electrical resistivity and seismic refraction. The GPR survey was conducted in the Old River Channel on the upstream side of the Low Sill structure. The high electrical conductivity of the water (~50 mS/m) precluded penetration of the GPR signal; thus, no useful data were obtained. The land-based surveys were performed on both northeast and southeast sides of the Low Sill structure. Both resistivity and seismic surveys identify a layered subsurface stratigraphy that corresponds, in general, with available borehole data and constructed geologic profiles. In addition, an anomalous area on the southeast side was identified that warrants future investigation and monitoring.

Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

2020 ◽  
Vol 25 (3) ◽  
pp. 415-423
Author(s):  
Ahmed Lachhab ◽  
El Mehdi Benyassine ◽  
Mohamed Rouai ◽  
Abdelilah Dekayir ◽  
Jean C. Parisot ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Electrical Current ◽  
P Wave ◽  
Low Resistivity ◽  
Refraction Tomography ◽  
Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

A geophysical investigation of the active Hockley Fault System near Houston, Texas

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. B177-B185 ◽  
Author(s):  
Shuhab D. Khan ◽  
Robert R. Stewart ◽  
Maisam Otoum ◽  
Li Chang
Keyword(s):  
Ground Penetrating Radar ◽  
Fault Location ◽  
Gravity Data ◽  
Time Lapse ◽  
Radar Data ◽  
Airborne Lidar ◽  
Fault System ◽  
Geophysical Investigation ◽  
Geophysical Surveys ◽  
Ground Penetrating

Sedimentation and deformation toward the Gulf of Mexico Basin cause faulting in the coastal regions. In particular, many active (but non-seismic) faults underlie the Houston metropolitan area. Using geophysical data, we have examined the Hockley Fault System in northwest Harris County. Airborne LiDAR is an effective tool to identify fault scarps and we have used it to identify several new faults and assemble an updated map for the faults in Houston and surrounding areas. Two different LiDAR data sets (from 2001 to 2008) provide time-lapse images and suggest elevation changes across the Hockley Fault System at the rate of 10.9 mm/yr. This rate is further supported by GPS data from a station located on the downthrown side of the Hockley Fault System indicating movement at 13.8 mm/yr. To help illuminate the subsurface character of the faults, we undertook geophysical surveys (ground-penetrating radar, seismic reflection, and gravity) across two strands of the Hockley Fault System. Ground-penetrating radar data show discontinuous events to a depth of 10 m at the main fault location. Seismic data, from a vibroseis survey along a 1-km line perpendicular to the fault strike, indicate faulting to at least 300-m depth. The faults have a dip of about 70°. Gravity data show distinct changes across the fault. However, there are two contrasting Bouguer anomalies depending on the location of the transects and their underlying geology. Our geophysical surveys were challenged by urban features (especially traffic and access). However, the survey results consistently locate the fault and hold significant potential to understand its deformational features as well as assist in associated building zoning.

Geophysical evidence for a large Holocene ice marginal moraine of Skeiðarárjökull, SE Iceland

2020 ◽  
Author(s):  
Devin Harrison ◽  
Neil Ross ◽  
Andrew Russell ◽  
Stuart Jones
Keyword(s):  
Surface Morphology ◽  
Environmental History ◽  
Sea Level ◽  
Low Frequency ◽  
Ice Age ◽  
The Holocene ◽  
Geophysical Surveys ◽  
History Of ◽  
Ground Penetrating ◽  
Surface Geomorphology

<p>The sedimentary record of Icelandic ice-contact environments provides valuable information about glacier margin dynamics and position, relative sea-level and the geomorphic processes driving proglacial environments. This important archive has been little exploited, however, with most glacier and sea level reconstructions based on limited sedimentary exposures and surface geomorphic evidence. Although geophysical surveys of Icelandic sandur have been conducted, they have often been of limited spatial scale and focused on specific landforms. Here, we report an extensive (42 km of data) detailed low-frequency (40 and 100 MHz) ground-penetrating radar (GPR) survey of the Sandgigúr moraine complex, SE Iceland, which transforms our understanding of this landform, with implications for the Holocene history of Skeiðarársandur and SE Iceland.</p><p>The Sandgigúr moraines are located on Skeiðarársandur, SE Iceland, down-sandur of large Little Ice Age-moraines of Skeiðarárjökull. They have a relatively subtle surface geomorphic expression (typically 125 m wide and 7 m high), and knowledge of their formation is limited, with no dating control on their age or detailed geomorphic or sedimentological investigations.  GPR investigations reveal a much larger (60 m high and 1200 m wide) and extensive buried moraine complex than that suggested by surface morphology, suggesting that the moraine was a major Holocene ice margin of Skeiðarárjökull.</p><p>GPR reflections interpreted as large progradational foresets (up to 20 m in height) beneath the morainic structure are consistent with a sub-aqueous depositional environment before moraine formation, providing potential controls on former sea-level.  The GPR data also provide information on the internal structure of the moraine, with evidence for glacitectonism within the proximal side of the moraine, multiphase moraine formation, and possible buried ice at depth. A 30-40 m thick package of down-sandur dipping GPR reflections drape the leeside of the moraine, evidencing glaciofluvial deposition during and after moraine development. Potential moraine breaches, possibly caused by glaciofluvial (e.g. jökulhlaup) events, are also apparent within the GPR data and the surface geomorphology.</p><p>We combine GPR-derived subsurface architecture with the current surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraines and surrounding region, from pre-moraine morphology, to their formation and breaching, resulting in the subsequent present-day morphology. These results provide new insights into the Holocene to present-day evolution of Skeiðarársandur and Skeiðarárjökull, with implications for reconstructions of the Holocene environmental history of SE Iceland.</p>

scholarly journals Preliminary geophysical investigation for road construction using integrated methods

2018 ◽  
Vol 65 (4) ◽  
pp. 199-206
Author(s):  
Joel Olayide Amosun ◽  
Gbenga Moses Olayanju ◽  
Oluseun Adetola Sanuade ◽  
Tokunbo Fagbemigun
Keyword(s):  
Geophysical Methods ◽  
Low Frequency ◽  
Road Construction ◽  
Electrode Spacing ◽  
Geophysical Investigation ◽  
Near Surface ◽  
The Road ◽  
Geophysical Surveys ◽  
Integrated Methods ◽  
Resistivity Meter

AbstractIntegrated geophysical methods have been used to investigate the competency of the subsoil. The geophysical surveys conducted involve very low-frequency electromagnetic (VLF-EM) and electrical resistivity (ER) methods (dipole-dipole). ABEM Wadi and Ohmega resistivity meter were used to acquire VLF-EM and ER data, respectively, along two traverses. Station interval of 5 m was used for the VLF-EM survey, while inter-electrode spacing for dipole–dipole was 10 m; the inter-dipole expansion factor (n) ranged from 1 to 5. KHFFILT software was used to generate VLF-EM profiles and pseudosection, while DIPRO software was used for ER. Results from the ER method revealed the pattern of resistivity variations within the study area. The low resistivity values (11–25 Ohm-m) observed at the southern part of the study area could be attributed to changes in clay contents and degree of weathering in the subsurface. The results from the VLF-EM investigation revealed the presence of near-surface linear geologic structures of varying lengths, depths and attitudes, which suggest probable conductive zones that are inimical to the foundation of the road subgrade.

An Integrated Application Ground Penetrating Radar and Seismic Refraction for Non-Intrusive Investigation of Geophysical and Geotechnical Targets

2018 ◽  
pp. 138-149
Author(s):  
Kebabonye Laletsang ◽  
Lucky Moffat
Keyword(s):  
High Resolution ◽  
Ground Penetrating Radar ◽  
Seismic Refraction ◽  
Environmental Applications ◽  
Geophysical Exploration ◽  
Background Theory ◽  
Geophysical Surveys ◽  
Ground Penetrating ◽  
Reciprocal Method ◽  
Profile Technique

This chapter presents a brief synopsis of geophysical exploration methods useful in geotechnical and environmental applications. The treatment is keyed at the baccalaureate level to enable geophysics graduates to apply these methods with minimal supervision. In the seismic method, the background theory is given. Application emphasis is placed on the reversed refraction profile technique which ultimately allows interpretation using the Generalized Reciprocal Method (GRM) first introduced by Palmer in 1986. The latter part of the chapter provides a review of the Ground Penetrating Radar (GPR) method used in high resolution geophysical surveys. This method has recently been used extensively to map defects developed on ageing road and pipeline infrastructure in Botswana. The treatment of theory is restricted again to suit the baccalaureate level of geophysics courses at university and many application examples are given. A discussion on acquisition parameters is included to guide the reader through implementation of the method.

scholarly journals Shallow geophysical techniques to investigate the groundwater table at the Great Pyramids of Giza, Egypt

2019 ◽  
Vol 8 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Sharafeldin M. Sharafeldin ◽  
Khalid S. Essa ◽  
Mohamed A. S. Youssef ◽  
Hakan Karsli ◽  
Zein E. Diab ◽  
...  
Keyword(s):  
Water Table ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Groundwater Table ◽  
Near Surface ◽  
Groundwater Aquifer ◽  
Geophysical Surveys ◽  
Subsurface Layers ◽  
Average Water ◽  
Ground Penetrating

Abstract. The near-surface groundwater aquifer that threatened the Great Pyramids of Giza, Egypt, was investigated using integrated geophysical surveys. A total of 10 electrical resistivity imaging, 26 shallow seismic refraction, and 19 ground-penetrating radar surveys were conducted in the Giza Plateau. Collected data for each method were evaluated by state-of-the art processing and modeling techniques. A three-layer model depicts the subsurface layers and better delineates the groundwater aquifer and water table elevation. The resistivity of the aquifer layer and seismic velocity vary between 40 and 80 Ωm and between 1500 and 2500 m s−1, respectively. The average water table elevation is about +15 m, which is safe for the Great Sphinx, but it is still subjected to potential hazards from the Nazlet El-Samman suburb where the water table elevation reaches 17 m. A shallower water table at the Valley Temple and the tomb of Queen Khentkawes, with a low topographic relief, represents severe hazards. It can be concluded that a perched groundwater table is detected in the elevated topography to the west and southwest that might be due to runoff and capillary seepage.

Application of geophysical methods for the investigation of the large gravitational mass movement of Séchilienne, France

2005 ◽  
Vol 42 (4) ◽  
pp. 1105-1115 ◽  
Author(s):  
O Meric ◽  
S Garambois ◽  
D Jongmans ◽  
M Wathelet ◽  
J L Chatelain ◽  
...  
Keyword(s):  
Rock Mass ◽  
Mass Movement ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Time Lapse ◽  
Gravitational Mass ◽  
Electrical Tomography ◽  
Refraction Tomography ◽  
Geophysical Surveys ◽  
Geophysical Techniques

Several geophysical techniques (electromagnetic profiling, electrical tomography, seismic refraction tomography, and spontaneous potential and seismic noise measurement) were applied in the investigation of the large gravitational mass movement of Séchilienne. France. The aim of this study was to test the ability of these methods to characterize and delineate the rock mass affected by this complex movement in mica schists, whose lateral and vertical limits are still uncertain. A major observation of this study is that all the zones strongly deformed (previously and at present) by the movement are characterized by high electrical resistivity values (>3 kΩ·m), in contrast to the undisturbed mass, which exhibits resistivity values between a few hundred and 1 kΩ·m. As shown by the surface observations and the seismic results, this resistivity increase is due to a high degree of fracturing associated with the creation of air-filled voids inside the mass. Other geophysical techniques were tested along a horizontal transect through the movement, and an outstanding coherency appeared between the geophysical anomalies and the displacement rate curve. These preliminary results illustrate the benefits of combined geophysical techniques for characterizing the rock mass involved in the movement. Results also suggest that monitoring the evolution of the rock mass movement with time-lapse geophysical surveys could be beneficial.Key words: gravitational movement, geophysical methods, Séchilienne.

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