Some important factors, such as rock strength, socket roughness, socket geometry, rock mass fracturing and possible bentonite/wall smear effects for drilled shafts, all affect the capacity of the pile foundation socket into rock. Weighting of these factors on pile capacity still needs further studys and is not taken into account in the design code. Hence, a pile load test is still common for each particular project to estimate the capacity of rock socket piles. In this paper, two compressive and two uplift pile load tests conducted for drilled shafts socket in Andesite rock in Taipei are studied. Studies on frictional resistance of the socket resulted from tesd results are compared to the available empirical rules.
This article investigates the evolution on tunnel structural safety management and safety inspection through viewpoints of inspection technologies, evaluation methods and relevant guides for management. The correspondingly up-to-date tendencies are then introduced and commented accordingly. Two non-destructive technologies regarding tunnel lining inspection, the spreading and mosaic technology for assembling tunnel lining image as well as the profile–image method for lining surveying, are proposed to meet the requirement from the up-to-date tendency. The former spreads the images taken from digital camera, and then mosaics them to obtain a spreading layout of tunnel lining surface. From which the description of anomalies layout on lining surface will benefit, so as the tracing on the variation of those anomalies. The latter utilizes profile–image technology to figure out the coordinates of whole-shape profile to be measured by ways of an image, capturing the profile illuminated by laser, taken by digital camera. The proposed technologies respectively provide simple approaches for identification on the variation of lining anomalies as well as deformation pattern, both of which required by the modern tunnel management of structural safety.
Jacking force requirement and alignment control are the main issues for pipejacking, especially for those cases with longer or curved alignment. Application of lubricant could be the most popular way to reduce the friction, so as to reduce the jacking force and increase the advancing rate. The lubricant can fill and support the gap between pipe and soil, such that collapse can be avoided and friction can be reasonably reduced. However, the pipe-soil interaction during pipejacking is complicated and considerably depends on the geological conditions. It is difficult to directly quantify the frictional behavior of the interface between pipe and soil. An indirect measurement with engineering adjustment is the practical way to quantify the frictional behavior. In this study, focusing on the common lubricants for pipejacking, a simple test method was adopted and applied to the pipejacking in Taichung gravel formation area. Based on the test results, the performance of the different lubricants was discussed. Besides, finite element method was also applied to simulate pipe-soil interaction with consideration of different interface properties.
The mudstone exposed at the foothills of Southwestern Taiwan is lithified shortly and poorly cemented. Therefore, the mudstone is rigidly hard in the dry state, but it swells and slakes easily when it absorbs water. The surface erosion, shallow slope failure, and the intensive gully are often observed at mudstone slopes due to the erosions caused by rainfall and runoff. In addition, the eroded mudstones of the slopes at the reservoir tend to fall and then deposit, which is believed to shorten the operation life of the reservoir.
This study reviewed available literature in investigating the physical and mechanical properties of the mudstone at the Southwestern Taiwan. The failures of conventional slope protections at the mudstone area are evaluated to investigate the individual failure mechanism. In addition, the new Soil-Tire-Vegetation method consisted of H-steel, filter layer, tire, and fill soils in the tire are proposed to protect the mudstone slope. The in-situ tests indicate that the new method has significant success in slope erosion prevention and vegetation.
In addition, the results of in-situ tests to simulate reservoir slope show that the slope with small slope angle and geotextile reduce slope erosion and produce fewer sediments to the bottom of the reservoir.
Due to complicated geological characteristics and structures in Taiwan, the accurate geological informations of tunnel project in the design stage are difficult to obtain. In order to minimize construction risk during tunnel construction, the supplementary investigations, either from tunnel face or ground surface, should be conducted for controlling geological conditions or solving critical geological problem. The results of these investigations can be provided as the information for minimizing construction risk and for future operation and maintenance. In this paper, an actual case of geological investigation during the construction of Tsengwen reservoir transbasin diversion tunnel is presented. Several investigation techniques including TSP seismic survey, horizontal boring, field rock experiments, supplementary ground drilling inspection, double packer test, DRISS survey, etc., were employed. The experiences gained from this case history may provide some valuable information for tunnel engineering.
Severely affected by chi-chi earthquake and devastating flood that followed due to typhoon and heavy rain, the tailrace tunnel, among others, of the Kukuan hydro power plant has to be realigned and rebuilt. The tailrace tunnel of total 1,991m long needs to underpass through the Tachia River for about 140m with rock cover only 3.5m. In view of the fact that weak zone normally developed along the river channel and thick debris accumulated on top of the river bed due to debris flows, the ground improvement from the surface is difficult. In dealing with the unique ground condition, a construction shaft and water sealing pre-grouting and supporting system were designed to prevent from the potential high water ingress when passing under the Tachia river. During construction stage, the contractor was allowed to select adequate excavation cross section, water sealing grouting, support elements and auxiliary treatment method to overcome the adverse ground condition. The contractor’s construction plane should be approved by the client before construction. Hopefully the experience learnt from this successful case can be shared by future project with similar condition.
Every year in typhoon season, the torrential rainfall frequently breaks off the roads and splits the retaining walls at the potentially hazardous slope above Lushan Hot Spring area. The repetitive and tedious road repairs have already been a burden to the highway authority. The slope gradually becomes a menace to the people in that area.
The study has been performed for 3 years and the slope movement mechanism was firstly understood. It is a creeping movement of a single sliding soft rock mass. The cleavages of the slope are highly weathered and sensitive to ground water level. The adverse orientation of weak plane aggravates the downward slope movement of weathered rock mass during torrential rain period.
Lushan Hot Spring has long been a major tourist attraction of Taiwan. The hazard potential of the slope also caught extensive public attention. This study delineates the slope geological investigations and instrument monitoring results for further reference.
Due to the improvement in the pixel resolution of digital cameras and in the efficiency of computer, the digital-image-correlation (DIC) technique gets much more attention than ever. The principle of DIC lies in comparing the grayscale relationship between the sub-images before and after the deformation, in order to determine the positions of the sub-image after deformation. It has advantages of a non-contact and high precise measurement technique. Two analysis modes , the point mode and the field mode based on finite element method, can be applied to calculate the digital-image-correlation function. In the point mode it can be applied to determine the positions of single or multi-points. In the field mode the digital image is discretized into grids in which the positions of these grids designated as nodes are analyzed. After the determination of the displacement, then the strain field can be calculated from the displacement gradient. Four application examples in this article are introduced: (1) the static and (2) the kinematics measurement of the full scale push over test in the Guan-Miao elementary school, (3) the plan strain compression test of the aluminum bicrystals and (4) the compression test of weak sandstone. It is found that the high precise measurement results have been achieved with the help of our self-developed analysis software and without expensive instruments. In addition, the deformation histories during processing have been visualized.
In the past, measurements on the mechanical characteristics of solid materials were carried out mostly in macroscopic scale (i.e., in millimeters), and microscopic scale studies were rare. In addition, most of the researches focused on the pre-failure behavior of materials, such as strength and stiffness before failure. Post-failure behavior, such as snap-back failure strength, was rarely addressed. In order to cover a full spectrum on the development of ductile to brittle failure of solid materials, and to achieve a complete load-displacement curve, a non-destructive electro-optical technique so-called ESPI (Electronic Speckle Pattern Interferometry) was developed. ESPI is a high resolution, full spectrum, real-time, and non-contact tool which is capable of delineating both the continuous ductile and non-continuous brittle deformation of solid materials.
ESPI was first use in the fields of electro-optical and mechanical engineering. Civil engineering researchers latter adopted this technique in laboratory tests such as indentation fracture test, three-point bending test, and Brazilian test, etc. to study the elasto-plastic behavior, crack initiation and propagation of solid materials. Observing the microscopic change of displacement on the surface of stressed material can lead to a full understanding of the macroscopic behavior of engineering materials. It is believed that the ESPI technique could help in the development of new materials and new methods for practical application in the future.