Non-destructive destructive testing is the merit of geophysics. The prospecting region of geophysical survey can extend to sky, surface, borehole, marine and underwater. Facing the complex geologic condition in Taiwan, geotechnical engineers need to accept and pay more attention to geophysics to jointly overcome the geological challenge. Applicable geophysical methods should be carefully selected and used prior to the design and construction phases. To improve understanding of the subsurface structure, a geologic model needs to be updated once new data were collected. This is the way to decrease the affectation of geology. In this paper, some practical and advanced geophysical methods are introduced. These methods include resistivity image profiling, 3D reflection seismics, borehole radar, borehole camera, acoustic televiewer log, dipmeter log and cross-hole log. The main purpose of this paper is to briefly introduce their operating principles and possible applications to geotechnical engineers for references.
MEASURING SUBSURFACE HYDROGEOLOGICAL PARAMETERS USING DOUBLE-PACKER TECHNIQUES
井孔量測技術包含地質鑽探(Borehole Drilling)、岩心鑑定(Core Logging)、岩石力學(Rock Mechanic Tests)、地球物理井測(Geophysical Well Logging)、地球化學(Geochemistry)及水文地質(Hydrogeology)特性試驗等項目。為能充份瞭解井孔內或附近地層岩性構造與量化數據，絕非上述單一技術可以克盡全功；因此各單項技術間需充份協調與合作，除可交互驗證調查或試驗資料外，亦可同時改進井孔量測技術與修正試驗方向，而使井孔獲得最大效益之資訊與數據。
本文主要目的除介紹各種地下水文地質特性之試驗方法與雙封塞搭配使用之新技術外，並選擇一測試井孔(約100公尺深)進行現場單井雙封塞注入試驗(Injection Test)與追蹤稀釋及擴散試驗(Tracer and Dilution Test)，以求取各裂隙段水力傳導係數值及流速值，同時亦將井孔微流速儀(Borehole Micro-Flowmeter)此項新科技如何用來研判井孔中主要流動層及裂隙段屬流入區(Inflow/Source)或流出區(Outflow/Sink)之技術做一說明。
Investigation techniques for characterizing subsurface geology and engineering environment are playing an important role in the booming of underground engineering explorations. Recently, several new investigation techniques which can be used through boreholes to determine useful parameters of subsurface formation have been developed. Such investigation techniques are generally called borehole measurements.
Borehole measurements include borehole drilling, core logging, rock mechanic testing, geophysical well logging, geochemical and hydrogeological testing etc. No single technique mentioned above can stand alone in characterizing the subsurface condition. In order to obtain the most valuable information, they must be used integrally and the results be cross-examined.
The major purpose of this paper is to introduce the subsurface hydrogeological testing methods with the aids of double packers. The techniques are applied in a test borehole about 100m deep to conduct the injection test and tracer dilution test for obtaining the hydraulic conductivity and flow velocity of fractures. Another new instrument called borehole micro-flowmeter for identifing the major flow zones is also introduced.
Repeat-pass satellite synthetic aperture radar (SAR) images having stable orbit baseline and high spatial resolution are good for the detection of surface deformation . The ability of measuring land subsidence is studied by using differential intreferometry (D-INSAR) techniques that are based on the SAR phase difference theorem .
In this research, we use multiple repeat-pass complex SAR images (1993、1996) from European Remote Sensing Satellite (ERS-1/2) to detect differential change in surface deformation on the order of centimeters in Taiwan Kao-Ping area. After the data processing by following steps : (1)data format conversion,(2) image registration, (3)interferogram generating, (4) baseline calculation,(5) earth curvature removal, (6)baseline fine-tuning, (7) phase unwrapping and DEM generation, the relationships between interferogram and surface deformation are established. The final work is to assess the feasibility of measuring land subsidence using the D-INSAR method .
The advantage of using an aerial photograph is that contain much topographic and physiographic information. However, performing measurements on it is much complicated than that on an orthophotomaps. Hence, this study tries to seek a solution which can generate ortho image from an aerial photograph. We calculated the six elements of exterior orientation by space resection method first, then created an ortho image of aerial photograph with collinearity condition equations according to a digital terrain model(DTM). The ortho image of an aerial photograph is geocoded thus can easily be integrated into Geographic Information Systems(GIS). We rectified the aerial photographs in Ba-Li area with two different years and digitized the coast line in GIS. Finally, we measured the change of coast lines during 15 years. Orthorectified aerial photographs may be applied in many applications, such as environmental change monitoring, measurement of the area of a landslide, etc. In a word, it is a useful tool to make the measurement on an aerial photograph easy and to assist in the study of ground surface changes.
With the assistance of graphical interface and database manage function, GIS(Geographic Information System) do improve the efficiency of seismic hazard analysis, such as rearranging the seismogenic zones and estimating the seismic parameters. In this study, we build seismicity and relevant data of Taiwan in Mapinfo, and also develop some modules for seismic hazard analysis. We could know it is very necessary and convenient to use GIS by some real case studies.
Using GIS is very beneficial for displaying or sorting earthquake data, and easier for the user to get the information he wants. In the same time, to overlap some relevant coverages assists us delineating and modifying the geometry of the seismogenic zones. The user could use the spatial data query functions of Maplnfo to sort the earthquake data directly in each seismogenic zone and then use the modules we develop to estimate the seismic parameters and to calculate the annual exceedance probability.
Using GIS to assist seismic hazard analysis could improve the rationality of rearranging the seismogenic zones and increase the data processing efficiency admittedly. In the future, It may be applied to seismic hazard mitigation program and structural resistant design fruitfully.
The Tunnel Profile Projection System is designed for displaying a preset tunnel profile on a plane. Utilizing a computer to generate the trajecting vectors of a Laser beam reflecting system from the predefined tunnel profile. The reflecting controller set the angular displacement and speed for both vertical and horizontal angular positioning system to reflect the Laser beam.
The trajectory of reflected Laser beam constructs a predetermined tunnel shape on a vertical plane from the Projection system. The Projected tunnel profile will help the operators effectively during the tunneling operation.
Taiwan Island is situated on the boundary between the Pacific plate and the Asia Continental plate. Geological structures such as faults, weak strata, joints and fractured zones and surge of ground water are frequently encountered in Taiwan island. These geological conditions are quite detrimental for tunnelling construction and generally result in the destruction of concrete lining after tunnelling completion. Many tunnels had been made in the mountain areas of Taiwan for transportation, hydropower and military purposes. The linings of these tunnels are damaged gradually after operating for many years and need to be inspected, refurbished and reinforced. Examples are introduced here to discuss the application of Ground Penetrating Radar and Visual scanning methods in the tunnel inspection for the lining condition and for the distribution of cave behind lining.
The numerical method of Discontinuous Deformation Analysis (DDA) was newly developed in 1980s. The mathematical principles are based upon the total potential energy which is similar to the Finite Element Method (FEM). However, DDA is capable of calculating discontinuous displacements (including separation, deformation, translation, and rotation) between elements. The author has been working on the applications and development of the DDA method for many years. It is believed that the method has a great potential in geotechnical engineering analysis, especially in the numerical simulation with large displacements and translations. This paper introduces DDA, the basic mathematical principles, and presents applications in the analysis of rockfalls and slope stability problems.
Stresses of the mooring line are influenced by several loads, such as wind load, wave load, anchor, and the friction between the mooring line and mud on sea floor. However, it is quite difficult to obtain an analytical solution due to its complicated dynamic responses. Consequently, model simulation conducted in the laboratory seems to be the best way to understand the behavior of the system. This paper reports a centrifuge modeling to simulate the responses of mooring line under monotonic and cyclic loads. The process of sample preparation and facility of testing are also included.