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Down-hole acoustic televiewer (ATV logging) is a geophysical well-logging device known to be able to reveal underground in-depth image. However, reviewing the current developments in the area of geotechnical engineering, ATV logging data were predominantly used for the purpose of visualizing and calculating the specific structural features in an open borehole, and nothing more. Noticeably, to the majority of engineering applications, it appears that ATV logging played a minor role compared to other geophysical borehole logging tools. Our study does not take it for granted. A systematic study is presented of the significance and consequent applications of ATV logging. The significance of correlation between acoustic amplitude and different geotechnical parameters is discussed and found to be consistent with previous findings. The result tells that ATV logging is actually able to provide timely and ground-truth information during site characterization, if properly used. Additionally, in our study, a simple rock mass evaluation index, Aco-RQD, is proposed, which is applicable to all aspects of geotechnical engineering as long as the continuous ATV logging data are available.

Drought and landslide are two common hazards that occurred in mountainous regions of Taiwan. This study is intended to develop a new concept of hazard prevention and management for solving both hazards simultaneously, in which the complex hazard has increased over the years in intensity and frequency due to climate variability and change. The proposed concept is a win–win solution that contains the feature of efficiency to mitigate two hazards together. When pumping groundwater as daily water demand at landslide-prone sites, the pore-water pressure decreases and the thickness of the unsaturated zone increases, which can result in stabilizing landslide-prone slopes and increasing flood storage capacity as an underground detention basin, respectively. Consequently, this approach can reduce the risk induced by the two hazards. To reinforce the effectiveness and instantaneity of hazard management, the technologies of smart sensing, smart transmission, and smart computing are then incorporated into a novel framework to develop an intelligent hazard prevention and management system. Thus, the groundwater supply-slope stability management system was installed and tested in the remote Kaoshi tribe, which is situated in Kaoshi Village of Mudan Township, Pingtung County, southern Taiwan. Hydrogeological issues for subsurface complexity, field investigations, and numerical modelling for preliminary evaluation and system design are also highlighted in this study. The developed system, which can offer valuable support for decision-making processes of hazard prevention, is capable of monitoring dynamic signals from various in-situ sensors, helping water resource allocations, and stabilizing hill slopes by means of drainage.

A simple and efficient improvement on the conventional packer testing technique is described. Based on experience associated with hundreds of packer tests in the past decade, a functional change is proposed with respect to the pressure inflation supply for the packer testing unit. The change involves allowing each packer to be independently controlled with two separate gas-flow delivery systems, allowing for independent inflation and decompression underground. Four types of packer set-up are presented, which are able to be used alternately, according to specific environmental needs. It is believed that this is a small but important technical solution for packer testing failures, particularly as regards low water-level conditions in the well, regardless of whether this is a natural effect or a result of the drilling operation.

On the assessment of groundwater potentiality in aquifers, a better understanding of the recharge patterns and flow pathways at the deeper depth is required but remains difficult. By studying the long-term temperature-depth variation data derived from using fiber-Bragg-grating (FBG) sensors, the objective of the present research is to discuss and demonstrate how this technique can provide information on the groundwater flow dynamics in a multilayered fractured formation. A series of borehole geophysical tests were first conducted to enable the characterization of the geological features and the presence of fracture flow. An array of 12 FBG sensors is deployed at multiple predetermined screening depths after well construction has completed, and the temperature-depth (T-z) trend line was established by fitting a polynomial curve to all the data points. The obtained temperature gradients in the upper depth of 5–80 m were found to be convex upward from January to April, uniform from May to July, and concave upward from August to December, which reveals a trend that the subsurface flow pattern actually varied throughout the year. In other words, groundwater recharge is not always a continuous steady‐state process, a significant time delay between rainfall and its substantial contribution to the aquifer as a form of deep groundwater recharge may take place and needs to be systematically investigated.

The application of inflatable-packer testing is commonly used in all sorts of geotechnical investigations. During the test, a frequently ignored problem is the unforeseen occurrence of leakage around the packers, which leads to a high risk to wellbore failure as well as equipment stuck. For the conventional design, once one of the two packer subjects to leakage, the field test would have to be immediately terminated. To cope with such problem, as proposed in this study, a modification of the pneumatic control device towards a 2-in-1 inflatable-packer system accompanying with the stratified analysis of hydrostatic pressure is required. The key idea is to let each packer element to be inflated separately and individually, as such their pneumatic responses can be fed to different control valves for diverse control tasks, of which the most crucial one is the in-situ conversion between single and double packer testing mode.

This paper presents an improved borehole prospecting methodology based on a combination of techniques in the hydrogeological characterization of fractured rock aquifers. The approach is demonstrated by on-site tests carried out in the Hoshe Experimental Forest site and the Tailuge National Park, Taiwan. Borehole televiewer logs are used to obtain fracture location and distribution along boreholes. The heat-pulse flow meter log is used to measure vertical velocity flow profiles which can be analyzed to estimate fracture transmissivity and to indicate hydraulic connectivity between fractures. Double-packer hydraulic tests are performed to determine the rock mass transmissivity. The computer program FLASH is used to analyze the data from the flowmeter logs. The FLASH program is confirmed as a useful tool which quantitatively predicts the fracture transmissivity in comparison to the hydraulic properties obtained from packer tests. The location of conductive fractures and their transmissivity is identified, after which the preferential flow paths through the fracture network are precisely delineated from a cross-borehole test. The results provide robust confirmation of the use of combined flowmeter and packer methods in the characterization of fractured-rock aquifers, particularly in reference to the investigation of groundwater resource and contaminant transport dynamics.

The observation of yield-drawdown response in the course of pumping test, as well as its derived application for aquifer characterization, is an essential practice in a geotechnical investigation. On the basis of that, for providing a reasonable estimate of aquifer transmissivity on site, a number of empirical models have therefore been proposed. Yet, the majority of previous studies are conducted based on investigations at homogeneous alluvial plain, very few, particularly in the case of Taiwan, are carried out focusing on mountainous fractured-rock aquifers. Aiming to address this problem, the observation data of 53 pumping tests obtained from a multi-years in-situ geological investigation program are analyzed, and the applicability of empirical log-log linear relationship between T and Q/s is examined. Our analysis reveals that the yield-drawdown responses derived from different geologic formations are quantitatively distinct, and those empirical rules derived from the alluvial landform should be used with care when applying in mountainous fractured-rock aquifers. Based on the analysis of statistical results in our study, with a systematic investigation and clarification of the Q-s relationship in advance, a satisfactory and cost-effective solution is obtained.

A simple descriptive-statistical approach is proposed for evaluating the transmissivity of fractured-bedrock under field conditions. Based on standard well logging and identification of structural discontinuities from borehole televiewer, the approach consists of four steps: (1) determination of discontinuity properties, namely the frequency of discontinuities and the ratio of open fractures along the borehole; (2) ranking the three well logs and the discontinuity properties into tertiles (high-to-low); (3) performing statistical analysis (F-test) for the three well logs to assess the significance of open fractures on the water-transmitting potential and then assigned a weighting factor; and (4) a semi-quantitative indicator, RGVFO, is obtained by multiplying all predictive indexes and weighting factors. It is a multi-criteria evaluation procedure that elucidates the quantitative and qualitative importance of all selected geophysical indexes. A high cross-correlation between transmissivity to RGVFO value is found, which indicates that by a combined consideration of well logging and structural discontinuities, an appropriate estimate of bedrock water-transmitting potential can be derived.

Drawing from the lessons learnt from the Fukushima nuclear disaster in Japan, the assessment of subsurface environmental hazard around nuclear power plants has emerged as a critical task. Consequently, aiming to better understand the possible environmental impact of radiation leaks into the groundwater, a prescreening programme was initiated in 2011 by the Taiwanese government. As part of this programme, this study conducted various borehole prospecting techniques to identify in situ hydrogeological characteristics at Chin-Shan Nuclear Power Plant. Borehole electrical log, sonic log and temperature/conductivity log were conducted to explain the regional lithologic conditions and permeability of the formation. In conjunction with this, the interwell tracer and pumping test was carried out to simultaneously determine the hydraulic parameters. In our opinion, the implementation of such in situ end-to-end investigations is essential in interpreting in situ fluid and solute transport dynamics prior to programming any numerical scheme for early warning, vulnerability assessment and regular monitoring of a nuclear power plant site.

The feasibility of using geological and geophysical well-log and borehole-televiewer data for the identification of hydraulically transmissive fractures is evaluated. Twenty-nine boreholes were drilled to a depth of 100 m in the middle-stream basin of Jhuoshuei River, Taiwan. Four criteria that assist in indicating the potential presence of permeable zones are proposed, including: lower gamma-ray response compared with the average response, divergence of the short normal-resistivity log relative to that of the long one, longer sonic travel time, and the appearance of discernible openings detected with the televiewer. With these, the transmissivities at the predetermined depths were estimated and verified by an in-situ hydraulic test. The statistical results indicate that, particularly in the mountainous area where a complex folded structure with a succession of synclines and anticlines is shown, the interpretation of lithologic conditions is not necessary to identify the presence of a relatively higher-permeability zone. Comparatively, the estimates of porosity and fracture aperture are the necessary premises to the prediction of hydraulically transmissive fractures. A joint consideration of all four criteria is found, allowing a less biased evaluation of the fracture transmissivity.

This study conducted different borehole prospecting techniques for hydrogeological investigations of fractured rock at three active landslide sites in southern Taiwan. Borehole televiewer logging, flowmeter logging, and packer hydraulic tests were performed to quantify various hydrogeological parameters including fracture width, fracture angle, flow velocity and hydraulic conductivity. The dependence of hydraulic conductivity on fracture properties was evaluated by correlation analysis. While a high positive correlation was found between hydraulic conductivity and fracture width ([Formula: see text]), and flow velocity ([Formula: see text]), no correlation with fracture angle was observed. In addition, it is worthwhile to note that the product of fracture width and flow velocity showed a strong correlation with hydraulic conductivity ([Formula: see text]). The regression analysis also revealed that a power law relationship, with a coefficient of determination of 0.83, exists between the hydraulic conductivity and the product of fracture width and flow velocity. The rationality of this relationship was carefully verified by using another group of geophysical borehole measurements. The results demonstrated that it is capable of predicting the hydraulic conductivity of fractured rock based on borehole televiewer and flowmeter logging results.

Groundwater and river-water have a different composition and interact in and below the riverbed. The riverbed-aquifer flux interactions have received growing interest because of their role in the exchange and transformation of nutrients and pollutants between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical transport model, which includes the unsaturated recharge zone, the aquifer and the riverbed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation for every flux on individual segments to the observed breakthrough curves of the resident concentration, and by inverse modelling for every flux simultaneously over the entire flow domain. The obtained transport-parameter relation was tested by numerical simulation using HYDRUS 2-D/3-D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of riverbed-aquifer flux interaction should take this into account.

Land subsidence basically is the deprivation of water and earth resources, further inducing social and economical undesirable impact. The principal direction of land subsidence prevention is properly management of groundwater. However groundwater management should be developed on the basis of combined technical, economical, social and institutional approaches to management that reflect local conditions and can be adapted and evolved. Therefore, the aim of this paper is to make land subsidence prevention strategies for government to refer. Before year 1969, agriculture was the main land utilization business in Pingtung Plain. Due to intensive development of fish breeding after 1970’s, the aquaculture area along the estuary region of Pingtung Plain have been dramatically increased. Groundwater thus became the main fresh water resource for aquacultural water diluting and flushing because of the insufficiency in surface water supply. The uncontrolled development of groundwater resources has led to undesirable effects, especially in the south where aquaculture is concentrated. These effects are land subsidence, saline water intrusion, lowering of water tables and reductions in well yields. Government stressed on the improvement of breeding technology in the past, which mainly focused on the water quality control in order to raise the culture density, however, it neglected the impact to the environment and quantity control. This paper promotes a reasonable aquacultural water consumption policy aims at finding out the most suitable breeding species considering water consumption and its reasonable breeding area under the premise that it will not depress the original profit of aquatic products trading.

This note is intended to provide comments on a recent study by Wang et al. (Eng. Geol. 198:1–15, 2015), in which they proposed a mechanistic model for determining the transmissivity of fractured rocks in an experimental well site. The authors claim that their model was developed based on a discrete fracture network concept, and verified with in-situ hydraulic testing results by statistical techniques. In this comment, we like to raise a few points of concern, rather than a criticism, regarding the essence of the proposed methodology that underpins this study.

In this work, the approaches to improve the organic solar cell with metal anode are studied. Under the hydrogen peroxide and ozone water treatment, the work function and surface roughness of metal anode are varied and hence to affect the fill factor (F.F.) and photocurrent of organic solar cells. By using hydrogen peroxide with diluted ratio of 1:70, the power conversion efficiency of the organic solar cell is increased from 0.34% to 0.81%. Under the ozone water treatment by 6 sec., the power conversion efficiency is increased from 0.34% to 0.99%.

Groundwater and river water with a different composition interact and exchange in the hyporheic zone. The study of hyporheic zone and its impact on water quality has recently received growing interest because of its role in nutrients and pollutants interactions between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical model, which include the unsaturated recharge zone, the aquifer and the river bed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation on individual segments to the observed resident breakthrough curves, and by inverse modelling on the entire flow domain for every flux. The obtained transport parameters relation was tested by numerical simulation using HYDRUS 2D/3D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of the hyporheic exchange of the water and dissolved materials should take this into account.