The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform

Liu Guo-zheng - One of the best experts on this subject based on the ideXlab platform.

  • Application of Shallow Seismic Refraction
    Coal Technology, 2009
    Co-Authors: Liu Guo-zheng
    Abstract:

    The shallow Seismic Refraction method is one of the main exploration methods of engineering,hydrogeological and environmental geology.According to the different geological conditions and investigation purposes in engineering geological investigation,with right application of the reasonable Seismic Refraction method,more obvious result of geotechnical engineering survey can be gained.

Koichi Hayashi - One of the best experts on this subject based on the ideXlab platform.

  • Non‐Uniqueness in Seismic Refraction Analysis
    Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011, 2012
    Co-Authors: Koichi Hayashi
    Abstract:

    Any Seismic Refraction analysis is essentially non-unique. In most cases, it is difficult to obtain a true velocity model from traveltimes observed only at the ground surface. Even with a one-dimensional two-layer model, it is impossible to obtain true thickness and velocity without a priori knowledge that the model is two layers. Non-uniqueness is a problem not only for the Seismic Refraction method but also for most geophysical methods in which underground physical property models are estimated from geophysical data observed at the ground surface. All Seismic practitioners and algorithm developers must admit this fundamental problem and try to develop alternative approaches. There are many approaches to reduce the non-uniqueness. Using priory information is the one of the most promising approach. It is well known that the result of a non-linear least squares inversion depends highly on the initial model. For instance, in the one-dimensional case, if we have a priori knowledge (perhaps from a downhole survey) that there are two layers, we can easily estimate a 1D true velocity function from a traveltime curve that indicates two layers. On the contrary, it is very difficult to estimate a true velocity function from the same traveltime curve if we know from other sources that they are actually three layers. Constraints during an inversion are also very important. Most of the geophysical inversions need spatial regularization in order to obtain stable results. During the inversion of the surface Seismic Refraction method, a constraint that velocity is increasing with depth is generally very effective. In this paper, we discuss the non-uniqueness of the Seismic Refraction method and demonstrate the importance of using appropriate initial model, constraints and model parameterization.

  • Application of High Resolution Seismic Refraction Method to Civil Engineering
    61st EAGE Conference and Exhibition, 1999
    Co-Authors: Koichi Hayashi
    Abstract:

    This paper presents a new method for the analysis of Seismic Refraction data. The algorithm of the analysis is based on traveltime tomography. The data acquired in the field care be analyzed almost automatically with high resolution and high accuracy by the use of the method.

Kuang Dai-zhi - One of the best experts on this subject based on the ideXlab platform.

Zhao De-heng - One of the best experts on this subject based on the ideXlab platform.

  • An overview of shallow Seismic Refraction methods
    World Geology, 2005
    Co-Authors: Zhao De-heng
    Abstract:

    The shallow Seismic Refraction method is one of the main methods of exploration for engineering,hydrogeological and environmental geology. According to the different geological conditions and investigation purposes in engineering geological investigation,with right application of the reasonable Seismic Refraction method,more obvious result of geotechnical engineering survey can be gained. This paper briefly looked back to the developing history of shallow Seismic Refraction method and carried on the simple introduction and comparison of various update interpretation methods. It presented some applied fields in engineering geologic investigation by the Seismic Refraction method.

Rosli Saad - One of the best experts on this subject based on the ideXlab platform.

  • application of 2d resistivity imaging and Seismic Refraction tomography to identify sungai batu sediment depositional origin
    Journal of Geology & Geophysics, 2017
    Co-Authors: Rosli Saad, M N Muztaza, M T Zakaria, M Saidin
    Abstract:

    Geophysical survey such as 2D resistivity imaging and Seismic Refraction tomography are non-destructive methods that widely used in subsurface exploration including archaeological study. The purpose of this survey is to identify the sediment deposition types of Sungai Batu area for Ancient River. Two study sites were chosen to conduct 2D resistivity imaging and Seismic Refraction tomography surveys. The 2D resistivity imaging survey was conducted using Poledipole array with 2.5 m minimum electrode spacing while Seismic Refraction tomography was performed using 5 kg sledgehammer as Seismic source with 5 m geophone spacing. Roll along techniques are apply for the two methods in the study site 1 and 2. The study concludes that the subsurface of the study area comprise of 3 major soil types. The top soil (1st type) consists of loose and dry alluvium which indicated with resistivity value of >100 Ohm.m. The second type was saturated alluvium (clay and sand) with resistivity and velocity values of 10-50 Ohm.m and 300 Ohm.m and >3600 m/s respectively. The correlation of 2D resistivity imaging and Seismic Refraction tomography show that the depositional environment for this survey is causes by land sediments deposit.

  • Applying the Seismic Refraction Tomography for Site Characterization
    APCBEE Procedia, 2013
    Co-Authors: I. N. Azwin, Rosli Saad, M. M. Nordiana
    Abstract:

    Abstract Seismic Refraction method is a geophysical method that has been developed for shallow subsurface investigation. It provides 2-dimensional profiles including depth and distance that simplified the characterization of relatively large volumes of the subsurface. Interpretation of Seismic Refraction data using Seismic tomography involves continuous velocity gradient across a subsurface which is more effective for site characterization compared to conventional Seismic Refraction. Three parallel Seismic Refraction survey lines were conducted at Kaki Bukit, Perlis with the aim of characterizing the subsurface of the area. 2m geophone spacing was used with total length of 46m. The separation between lines is 20m. Weight drop of 20 kg and steel plate were used as Seismic source. A total of 20 shotpoints were performed for survey line L1, 23 shotpoints for survey line L2 and 22 shotpoints for survey line L3. The high quality Seismic data obtained were then processed using SeisOptPicker and SeisOpt2D software to produce a Seismic tomography section for each survey line. Results indicate that the study area is said to have 4 main layers with velocity increase fairly with depth. The first layer with velocity 300-500 m/s predominantly consists of top soil and form overburden. Second layer with velocity 500-800 m/s is suggested to be a highly weathered limestone. The third layer represents by highly fractured limestone with velocity 800-1500m/s. Limestone bedrock represent by the fourth layer with velocity > 2000m/s. Competent limestone bedrock is identified at survey line L3 with velocity > 3000m/s.

  • Integration of Seismic Refraction and 2D Electrical Resistivity in Locating Geological Contact
    Open Journal of geology, 2013
    Co-Authors: Nisa’ Ali, Rosli Saad, M. M. Nordiana
    Abstract:

    The aim of this research is to locate the geological contact for engineering purpose applying Seismic Refraction and 2D electrical resistivity method. Resistivity and Seismic Refraction method was conducted on four survey lines with 3 lines running from NW to SE which about parallel to each other and 40 m apart while the fourth line was running from SW to NE. The 2D resistivity survey used minimum electrode spacing of 5 m and the survey used pole-dipole array with minimum current was 2 mA and maximum was 20 mA. The Seismic Refraction survey used 5 m geophone spacing with offset shot was + 30 m and - 30 m. Resistivity results generally show the area was divided into two main zones, alluvium with resistivity value of 10 - 800 ohm-m, and granite bedrock with resistivity value of > 2500 ohm-m. There is a geological contact between granite and alluvium. The Seismic results show the area consists of two layers. The first layer (top layer) with velocity of 460 - 900 m/s which was alluvium mixed with boulders. The second layer with velocity of 2060 - 3140 m/s with depth 71 - 90 MSL. The thickness of the overburden is 5 - 15 m.

  • Mapping of geotechnical data using Seismic Refraction studies
    2013
    Co-Authors: Mohd Hazreek Zainal Abidin, Rosli Saad, Fauziah Ahmad, Devapriya Chitral Wijeyesekera, Jamil Matarul, Mohamad Faizal Tajul Baharuddin
    Abstract:

    Geotechnical data mapping is important during the pre and post civil engineering construction particularly near or inside the geohazard area. Subsurface ground instability reflects difficulty of engineering investigation task especially to determine the possible subsurface ground instability zone for rehabilitation, maintenance and monitoring purposes. This study applied a Seismic Refraction method to investigate a geotechnical data for preliminary geotechnical and engineering geology assessment due to subsurface ground instability. The method used a concept of Seismic waves generated by one of several types of energy sources and detected by arrays of sensitive devices called geophones. The data was processed by Optim software for generating subsurface velocity distribution (primary velocity, vp) and interpretation with supported by existing borehole information. The result obtained three main velocity layers with possible subsurface ground instability zone which consisted of top soil/residual soil (350 – 600 m/s) 0 – 4 m, weathered zone with a possible mixtures of soil, boulder and rock fractured (500 – 1900 m/s) 2 – 23 m and fresh rock/bedrock (> 2300 m/s) from 6 m depth. The thickness and width of subsurface ground instability zone varies within the survey line from 3 – 20 m and 75 m respectively with a primary velocity of 700 – 1800 m/s. The Seismic Refraction survey produces a good relationship results compared to the borehole information in term of stratigraphy and geomaterials features. This study proved that the Seismic Refraction method was a good geophysical technique to be integrated in geotechnical mapping assessment since its covers a large area which extends the borehole data. The application of Seismic Refraction method can increase the effectiveness of geotechnical data in term of cost and time since it can determine the subsurface information in two dimensional (2-D) profiles rapidly by employing fewer workers compared to others conventional mapping techniques. In addition, this geophysical method used a surface technique that can reduce the site damageability during the data acquisition stages which can contribute the development in a sustainable build environment.

  • Seismic Refraction investigation on near surface landslides at the Kundasang area in Sabah, Malaysia
    Procedia Engineering, 2012
    Co-Authors: Mohd Hazreek Zainal Abidin, Rosli Saad, Fauziah Ahmad, Devapriya Chitral Wijeyesekera, Mohamad Faizal Tajul Baharuddin
    Abstract:

    Surface geophysical method was used in studying the effect of natural disaster impact and subsurface physical changes located in an active geohazard zone at the Kundasang area in Sabah, Malaysia. The natural disaster impact was a previous surface and subsurface ground damage caused by a landslides activity, and the consequent civil engineering infrastructure failure. 2D Seismic Refraction tomography (2DSRT) was used in evaluating the continuous subsurface ground damage with particular reference to geomaterials and landslide features based on compressional wave (Primary velocity, vp) results. A total of four spread lines were conducted in two different zones (Northeast and Southwest zone) in Kundasang Secondary School (SMK Kundasang). Primary velocity data was acquired and recorded using ABEM Terraloc MK6 seismograph with the Seismic wave being triggered by an impact and detected by arrays of sensitive devices called geophones. 2D Seismic Refraction primary velocity results representing subsurface profile for each survey line were calculated to determine time and depth of the subsurface profile investigated based on linear and delay time analysis supplied by Optim software package and supported by previous borehole data. The Seismic Refraction method identified three main layers of geomaterials which contained a subsurface landslides anomaly within the layers. The results consist of top soil/residual soil (330 600 m/s) 0 6m , weathered zone with a mixture of soil, boulder and rock fractured (500 1900 m/s) 2 25 m and fresh rock/bedrock (> 2300 m/s) from 8 m depth. The landslides geometry was determined inconsistently within the survey line from 3 25 m (thickness), 57 and 75 m (width) and 100 m and more (length) with a primary velocity of 700 1800 m/s. The Seismic Refraction profiles obtained also revealed that the landslide occurrence extends from the southeast zone and continuously heading towards the northeast zone. A good matching Seismic Refraction results was obtained and calibrated using borehole results which shows that this technique was appropriate to be applied in near-surface landslide assessment which can further substantiates and compliments borehole data and others physical mapping