Downhole Seismic Testing Research Articles

Integrating downhole seismic testing into dynamic probing light (DPL): first results

Dynamic probing light (DPL) is available among a wide range of dynamic penetrometers. This equipment can be used in locations where conventional sounding equipment may have limited access. Here, the shear wave velocity (Vs) determination by the downhole seismic technique is incorporated to the DPL to develop a hybrid test, the seismic DPL test, for the preliminary characterization of tropical soils. The corresponding equipment, test procedure and data interpretation of the seismic DPL (S-DPL) test are presented and discussed. S-DPL test campaigns were carried out at two experimental research sites where crosshole seismic tests were conducted to provide reference Vs profiles. The Vs profiles determined with the S-DPL test are in accordance with those determined with the crosshole test for both sites. The proposed hybrid test (S-DPL) has the potential to serve applications in preliminary site characterization, particularly at sites including unsaturated tropical soil profiles.

Soil disturbance evaluation of soft clay based on stress-normalized small-strain stiffness

Soil disturbance includes the change of stress state and the damage of soil structure. The field testing indices reflect the combined effect of both changes and it is difficult to identify the soil structure disturbance directly from these indices. In the present study, the small-strain shear modulus is used to characterize soil structure disturbance by normalizing the effective stress and void ratio based on Hardin equation. The procedure for evaluating soil sampling disturbance in the field and the further disturbance during the subsequent consolidation process in laboratory test is proposed, and then validated by a case study of soft clay ground. Downhole seismic testing in the field, portable piezoelectric bender elements for the drilled sample and bender elements in triaxial apparatus for the consolidated sample were used to monitor the shear wave velocity of the soil from intact to disturbed and even remolded states. It is found that soil sampling disturbance degree by conventional thin-wall sampler is about 30% according to the proposed procedure, which is slightly higher than that from the modified volume compression method proposed by Hong and Onitsuka (1998). And the additional soil disturbance induced by consolidation in laboratory could reach about 50% when the consolidation pressure is far beyond the structural yield stress, and it follows the plastic volumetric strain quite well.

The Effect of Vertical Ground Motion in Dynamic Analysis for Near Fault Area in Yogyakarta

Indonesia is surrounded by three major tectonic plates which are Indian-Australian, Eurasian and Pacific tectonic plates. Consequently, Indonesia is prone to seismic hazard. Horizontal ground motion has taken a major role in conducting nonlinear time histories analysis or in assessing liquefaction potential. However, for site near fault area, vertical ground motion can be quite significant and cannot be neglected. This paper aims to evaluate the effect of vertical ground motion in the near fault area by conducting dynamic analysis using MIDAS GTS NX. UBC Sand model is employed to model liquifiable material. Standard penetration test, laboratory test and downhole seismic tests are conducted at the site in order to characterize the shear wave velocities and properties of the soil at the area and to determine the thickness of the liquifiable layer. For this paper, two dynamic analyses will be conducted. For first analysis, only horizontal ground motion is applied to the model while in the second analysis, both horizontal and vertical ground motion will be applied. Based on dynamic analysis result, the horizontal surface motion and horizontal surface response spectrum that is propagated using bi-directional time histories will have bigger acceleration if being compared by only using horizontal time histories.

Application of Dynamic Time Warping to Determine the Shear Wave Velocity from the Down-Hole Test

A tailing storage facility (TSF) is a complex hydrotechnical structure that requires continuous monitoring to prevent catastrophic dam damage. One critical issue to control is the soil’s characteristics, which is why many field and laboratory tests are carried out on the dam to determine the relevant soil parameters. Among these tests, down-hole seismic tests, such as SCPT, are performed to determine, e.g., the shear wave velocity. However, accurately calculating the difference in the times of the arrival of the wave at the two geophones is crucial to determining its value. This article proposes a novel method for estimating this variable using the DTW (Dynamic Time Warping) algorithm, which calculates the shift between two signals by determining their optimal match. The article also addresses signal interference and proposes methods for clearing it to obtain more accurate results. Furthermore, the article introduces a method for measuring the signals’ quality based on their similarity, which helps assess whether determining the shear wave velocity is possible for a given sample.

Prediction of the static elastic modulus of limestone using downhole seismic test in Asmari formation

Prediction of the static elastic modulus of limestone using downhole seismic test in Asmari formation

Reducing computational costs in site response analysis and its application for the nonlinear dynamic analysis of structures

In this paper, the wavelet transform is used for the first time to reduce the cost of site response analysis calculations for different soil profiles in Isfahan city. This downsampling method was used up to three levels to generate approximate waves from the ground motion records. Site response analysis was done using the one-dimensional equivalent linear and nonlinear method. Down-hole seismic tests of 71 boreholes in Isfahan city were used to make different soil profiles. In addition, 30 ground motions compatible with seismic hazard analysis of this city were selected. Due to the lack of comprehensiveness in previous studies, none of them has definitively indicated which level of wave decomposition is the last reliable wavelet filter. But in this article, for the first time, by performing a data reliability review, it is shown that the last reliable filter for the site response is related to the second level of decomposition. Comparison of the site response analysis using approximate waves and the main records, by performing more than 2100 analyses, showed that wavelet transform could be used up to two levels with the maximum error of 8% in predicting amplification factors. In addition, approximate waves were used for the nonlinear dynamic analysis of structures with different heights located at different soil profiles, and results showed that wavelet transform decreases the cost of calculations up to 50% with a 5% error.

COMPARATIVE ANALYSIS OF STATIC SHEAR MODULUS AND DYNAMIC SHEAR MODULUS DETERMINED BY GEOPHYSICAL AND GEOTECHNICAL INVESTIGATION

Due to the occurrence of earth tremors which leads to the vibrations of foundations and perhaps failure of buildings and roads, it is therefore important to understand and have knowledge of the geomechanical soil properties for foundation design, assessment of risks and suggestion of mitigation plans in engineering structures and road construction. A total of 3 boreholes were drilled with the Standard Penetration Test (SPT) performed and Downhole Seismic Test (DST) carried out in the boreholes located within Assa to investigate the Geomechanical soil properties in the area. For the geophysical survey, the downhole seismic test was carried out to determine the P-wave and S-wave. The results were processed using the generalized reciprocal method (GRM) with the Seisimager program. The results of soil dynamic modulus (shear, young and bulk modulus) and Poisson ratio recorded from DST conducted in BH1, BH2 and BH3 ranges from 7300 KPa to 72390 KPa, 0.31 to 0.41 for the Poisson ratio. Meanwhile, soil static modulus and Poisson’s ratio recorded from SPT conducted in BH1, BH2 and BH3 ranges from 2520 to 44687.0 KPa, 0.20 to 0.55 for the Poisson ratio respectively. The results of this study have shown that there is a wide variation between geomechanical properties derived from geotechnical investigations (static properties) and geophysical investigations (dynamic properties). Based on depth trend analysis, the dynamic and static soil elastic properties all increases with depth. Generally, the dynamic soil properties were significantly higher than the static elastic properties. At shallow depths (<12.0 m), the difference between static and dynamic soil modulus was relatively small, but increased with increasing depth. Meanwhile, the difference between static and dynamic Poisson ratio was high at shallow depth and it decreased with increased depths where they almost overlap. Correlation between the derived static and dynamic properties all revealed positive correlation trends. The strength of the correlation was highest for young modulus (r=0.87) which was closely followed by the shear modulus (r=0.63). Meanwhile, Poisson ratio (r=0.40) and bulk modulus (r=0.23) revealed weak positive correlation trends. The regression models generated from this study were used to derive static elastic properties and compared with the static properties obtained from geotechnical investigation thereby deriving the equations Dynamic Shear Modulus = (1.4207 x Static Shear Modulus) + 5022, Dynamic Young Modulus = (2.0241 x static young modulus) + 5054.8, Dynamic Bulk Modulus = (1.7852 x static bulk modulus) + 15458, Dynamic Poisson’s ratio = (0.1812 x Static Poisson’s ratio) + 0.3154. The results showed fairly good match between static (geotechnical) shear modulus and static (from regression model) shear modulus, static (geotechnical) young modulus and static (from regression model) young modulus. There was no good match obtained for bulk modulus and Poisson ratio generally, except at shallow depth (< 12 m depth) where Poisson ratio revealed a good match.

Liquefaction analysis of sandy soil during strong earthquake in Northern Thailand

Northern Thailand has experienced several earthquakes which led to soil liquefaction in the past few decades. Traditional methods of evaluating liquefaction potential involve standard penetration test (SPT) or cone penetration tests. This research augmented experimental results with numerical methods to evaluate the liquefaction potential of Mae Lao Sand in Chiang Rai province of northern Thailand. SPT and downhole seismic test data collected during a field investigation at the Mae Lao site were compared to a 1D site response model analysis of the site. A series of undrained monotonic and cyclic triaxial tests was conducted on Mae Lao Sand specimens with different initial void ratios and confining pressures. Cyclic triaxial test results with varying deviator stress amplitudes were used to draw liquefaction resistance curves. Results from numerical simulation of sand liquefaction were used to characterise the stress–strain-pore water pressure response of Mae Lao Sand. 1D site response analysis determined seismic responses with different geological and groundwater conditions. All put together, the results showed that pore water pressure ratio decreases with increasing sand stiffness, the thickness of a soil layer significantly increases its liquefaction potential, and in-situ conditions and groundwater depths have major influences on the liquefaction potential of sand layers.

Seismic Waves Response Characteristics of Niger Delta Soils

The study investigated the dynamic soil properties of States in Niger Delta region of Nigeria as a function of seismic activities. The down-hole seismic test was used to determine the response of the soils. The results of soil samples collected up to 30m depth, showed that the average young modulus increases with increase in depth, which ranged from 115.77±1.74 to 3231.17±1.01 kPa across the States. Also, shear wave velocity generally increases with increase in depth. The average shear wave velocity across the States ranged from 126.00±1.86 to 288.00±2.63m/s. Also, the average P-wave velocity increases with depth, with values across the States ranging from 310.60±3.51 to 656.00±3.69m/s. On the other hand, the void ratio was observed to be constant at certain range of depth, and in most with values across the States ranging from 0.651±.093 to 0.860±.067. Unlike void ratio, Poisson’s ratio fluctuates with depth, with values across the States ranging from 0.23±2.27 to 0.36±1.18. Based on the results, the Niger Delta region may be resistant to earthquake, but as an oil hub of Nigeria, it is also susceptible to earthquake that could be triggered by stress due to heavy load and seismic activities.

Static and dynamic characterization and response analysis of soils from northern India

Experimental investigations on soil samples collected from the sites of Baraut, Noida and Mandi in North India have been performed to study the static and cyclic behavior of soil. Liquefaction potential of the sites near Himalayan range is also carried out. The SPT and downhole seismic tests have been performed for the estimation of static and dynamic properties of soil. Strain-controlled cyclic triaxial tests are also carried out on soil samples collected from the borehole at various depths up to 30 m for the evaluation of dynamic soil properties. The study examined the effects of parameters such as cyclic shear strain, loading frequency and overburden pressure on the cyclic behavior of the soil. One- and two-dimensional dynamic response analysis has been performed on three sites. The initiation of initial liquefaction ranged from 202 to 752 cycles for the Baraut site, 212 to 722 cycles for the Noida site, and 121 to 617 cycles for the Mandi sites. The final design response spectra of the sites are obtained from 1D ground response analysis. The results from the response analysis have been compared with the reported results. The soils from the present study areas are prone to liquefaction at 10 m to 15 m from the ground surface.

Assessment of land subsidence as an environmental threat facing Dammam city, eastern Saudi Arabia based on soil geotechnical parameters using downhole seismic approach

To meet the increasing in population, urbanization and public transportation needs of Dammam big city a new transportation infrastructure network is planned and being developed. In the same time, environmental threats of land subsidence on network has been raised and needs to be addressed.Site characterization for designing this transportation lines is crucial to ensure reliable and economic substructure design, because weak site soil conditions may cause land subsidence problems. Downhole seismic (DS) testing is commonly used to determine compression wave (P) and shear wave (S) velocity profiles in geotechnical engineering, which are required in evaluating responses to shaking of geotechnical sites and structures. A DS survey was conducted through boreholes at the center of the Dammam metropolitan city, Saudi Arabia. A sledgehammer horizontally striking a wooden plate generated shear (S) waves polarized in the crossline and inline directions, whereas a vertical hammer hitting a metal plate generated the P wave. Data were obtained using Freedom Data PC, a downhole tool with a triaxle geophone package, and a seismograph. In the downhole technique, the geophones were equestrian on an internal rotating block, and a built-in fluxgate compass as well as servo motor system maintained the orientation of the geophones inside the borehole. The instrumentation and processes complied with the standard test methods for downhole seismic testing (Standard and D7400-08, 2008). This represents, a versatile platform for evaluating structures/infrastructures and geophysical seismic engineering surveys. The estimated seismic velocities were used in estimating the various elastic moduli and density variations within the mapped boreholes. The integrated approach of proper geotechnical characterization and 1D velocity profile proved to be a helpful tool for assessment of subsidence of Dammam city in the future which, in turn, will reduce the environmental threats facing the city.

Hydro/Engineering Geophysical Parameters and Design Response Spectrum for Sustainable Development in Ras Muhammed National Park, Sinai

The Egyptian government is preparing a sustainable development master plan for the Ras Muhammed National Park (RMNP), south Sinai. Noteworthy, the scarcity of the freshwater resources and close proximity to the active seismic zones of the Gulf of Aqaba implicate geophysical investigations for the fresh groundwater aquifers and construct a design response spectrum, respectively. Accordingly, 14 VESs, hydro/engineering geophysical analysis, pumping tests, downhole seismic test, a design response spectrum for buildings, and borehole data were carried out in the study area. The unconfined freshwater aquifer was effectively depicted with true resistivities, thickness, and EC ranged from 56 to 135 Ω m, 11 to 112 m, and 1.4 to 7.1 mS/m, respectively. The Northeastern part was characterized by higher aquifer potentiality, where coarser grains size, highest thickness (112 m), high true resistivity (135 Ω m), groundwater flow (0.074 m3/day), tortuosity (1.293–1.312), formation resistivity factor (4.1–4.6), and storativity (0.281–0.276). An increase in pumping rate was accompanied by an increase in well loss, increase in aquifer losses, decrease in well specific capacity, and decrease in well efficiency. Design response spectrum prognosticated the short buildings (<7 floors) in RMNP to be suffering from a high peak horizontal acceleration and shear forces for acceleration between 0.25 and 0.35 g. Therefore, appropriate detailing of shear reinforcement is indispensable to reduce the risk of structural damages at RMNP.

Methodology for Processing Seismograms Containing Total Internal Reflections

A very common problem encountered in downhole seismic testing (DST) and crosshole seismic testing (CST) is the processing of seismograms that contain total internal reflections (TIRs). TIRs arise when the incident angle exceeds the critical angle, and they are associated with reflected source wave distortions due to the fact that the reflection coefficients become complex. TIRs are typical in CST investigations (since horizontally traveling source waves have high angles of incidence on bounding stratigraphic layers), whereas in DST investigations, TIRs are encountered whenever there are significant man-made structures (piles, stone columns, and deep underground structures such as deep basements, parking garages, and dam structures). To process seismograms containing TIRs, time-variant blind seismic deconvolution (BSDtv) techniques are required, and this paper outlines a new formulation of a previously published concept in blind seismic deconvolution referred to as principle phase decomposition (PPD). This new PPD filter formulation allows for BSDtv where the direct source wave is isolated from the reflected source waves. The BSDtv PPD filter formulation is referred to as BSDSolver-tv.

In-situ assessment of the dynamic properties of municipal solid waste at a landfill in texas

An understanding of dynamic properties of Municipal Solid Waste (MSW) is essential for seismic response analysis of MSW landfills in areas of moderate to high seismicity. A field testing program aimed at characterizing the dynamic properties of MSW was executed at two locations in a Subtitle D landfill in Austin, Texas. Shear and primary wave velocities were measured using small-scale crosshole and downhole seismic tests. The combination of these seismic methods allowed an assessment of the effect of waste composition on dynamic properties, anisotropy, and Poisson׳s ratio of the MSW. In addition, steady-state dynamic testing was performed using two mobile vibroseis shakers to evaluate in-situ the nonlinear relationship between shear modulus and shearing strain. Horizontal steady-state shaking at increasing stress level generated shearing strains from 0.001% to 0.2% allowing evaluation of shear modulus reduction curves over a wide shearing strain range. The effect of confining stress on the dynamic properties of the MSW was also evaluated using the substantial weight of the vibroseis as reaction to apply surcharge vertical loads at the surface of the MSW.

Signal Processing Challenges When Processing DST and CST Seismic Data Containing TIRs

Downhole Seismic Testing (DST) and Crosshole Seismic Testing (CST) are important geotechnical testing techniques which provide for low strain (

Gmax of Reclaimed Ground on the Western Coast of Korea Using Various Field and Laboratory Measurements

The maximum shear modulus of soil is a principal parameter for the design of earth structures under static and dynamic loads. In this study, the statistical data of the maximum shear moduli of reclaimed ground in the Songdo area on the western coast of Korea were evaluated using various field and laboratory tests, including the standard penetration test (SPT), piezocone penetration test (CPTu), self-boring pressure meter test (SBPT), down-hole seismic test (DHT), seismic piezocone penetration test (SCPTu) and resonant column test (RCT). Soils were classified variously by using a conventional unified soil classification system and classification charts for CPTu data. For the soils containing mostly sand and silt, the soil classifications using the classification charts for CPTu data show good agreement with the unified soil classification. Based on the statistical analysis on various maximum shear moduli, new site-specific empirical correlations between the shear moduli and SPT and CPTu values were proposed. Predictions of the maximum shear moduli using the proposed correlations were compared with the data obtained from the DHT, which is comparatively exact in evaluating the maximum stiffness of soils. The good agreement confirmed that the proposed correlations reasonably predicted the maximum shear moduli of soils in western coastal area of Korea.

A Small, Lightweight Borehole Receiver for Crosshole and Downhole Seismic Testing

Abstract Crosshole and downhole seismic testing have traditionally employed the use of a downhole receiver consisting of geophones in a sealed container along with a separate inflatable bladder for seating the geophones against the inside of the boring. This configuration has been used with success, but these receivers can be relatively large and heavy. As an alternative, a smaller, lighter borehole receiver design has been developed. The prototype tool is approximately 19 cm (7.5 in.) long and 6.4 cm (2.5 in.) in diameter, and it weighs less than 0.68 kg (1.5 lb). The new design is a single pressuremeter-like unit in which small accelerometers are glued to the inside of an inflatable membrane. When inflated, the accelerometers are pressed against the borehole wall or casing, and excellent coupling is achieved. Typical results from field testing indicate that the new tool produces reliable results.

Developing a System for Down-Hole Seismic Testing Together with the CPTU

. This paper presents a system for performing down-hole seismic test together with the piezocone test in order to determine the shear wave velocity (Vs) and for calculating the maximum shear modulus (Go); a basic parameter for analyzing the dynamic soil behavior and a reference value of the soil stiffness. The system components are described and tests results for checking the geophone response are also presented, both before and after installation into the probe. The system was used in down-hole tests carried out at three experimental research sites located in the interior of Sao Paulo State, Brazil, where in situ seismic test results are available. The Vs values measured in down-hole tests carried out with this system were consistent with those determined in cross-hole tests and with a commercial seismic piezocone, which enabled to validate the developed system.

Quality Assessment and Quality Control of Deep Soil Mixing Construction for Stabilizing Expansive Subsoils

This paper presents the process and results of a quality management program performed during and immediately after the construction of two deep soil mixing (DSM) test sections. The quality management program consisted of laboratory, in situ, and mineralogical tests to address the effectiveness of the treatment during and after construction. In situ investigations including the down-hole seismic and spectral analysis of surface waves (SASW) test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the columns and surrounding soils. Scanning electron microscopy and electron dispersive x-ray analysis were performed on raw, laboratory treated and field-treated specimens for qualitative understanding of the degree of mixing achieved in the field and the compounds formed at particle level during stabilization, respectively. Laboratory tests results on field cores indicated that both field stiffness and strength are about 20 to 40% less than the corresponding laboratory prepared soil samples. The down-hole seismic and SASW tests showed considerable improvement in stiffness in and around the DSM columns. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of lime-cement treated clay particles in both laboratory and field specimens, suggesting adequate mixing of the soil and binder in both environments.

Spectral Analysis of Ground Acceleration-Based Testing

Spectral analysis of downhole acceleration data is used to identify changes in elastic properties of track substructure. The spectral analysis is based on the power spectral density (PSD) as an indicator of frequency content. This method was developed and tested at the Transportation Technology Center, Inc., in Pueblo, Colorado. The system provides an efficient means for monitoring track bed to predict settlement and deformation conditions that would require maintenance. The method relies on a triaxial piezoelectric accelerometer inserted into a permanently installed inclinometer casing installed into the subgrade. Periodic measurement of the dynamic ground response allows for the identification of changes in the small strain elastic properties of the substructure layers. The methodology uses conventional downhole seismic shear wave velocity testing. For the purpose of comparison, test sections were constructed with clean and fouled ballast. Shear wave velocities indicated the differences in material properties. PSDs of the signals were analyzed to determine variation resulting from differences in soil conditions. PSDs were calculated at different intervals of loading. With increased loading, settlement of the subtrack soils occurs. The densifi-cation can be seen as an increase in the predominant frequency of the PSD. The PSD from the section with the clean ballast had a higher predominant frequency than the PSD from the section with the fouled ballast. A decrease in predominant frequency over time would indicate the decrease in stiffness and the potential of increased fouling of the ballast with fines. Changes in the frequency content would indicate changes in elastic response.