Assessment of hydraulic conductivity improvement due to vibration application at riverbank

Groundwater abstraction is a process of obtaining subsurface water sources for variety purpose of consumption. However, due to long and continuous pumping, the efficiency might decrease because of soil clogging. This decreased can be quantified and reflected as the change of hydraulic conductivity (K) values at the pumping site. This study aims to assess the variability of soil hydraulic conductivity at groundwater pumping site and also to study the effectiveness of vibration method to improve the hydraulic conductivity by comparing the result of before and after vibration is applied. The study was carried out by measuring the K values using slug test at wells MW01 and MW02 with two durations of vibration which were 45 minutes and 60 minutes. The result shows that values of hydraulic conductivity of the soil were found to have increased for both MW0l and MW02 wells. On first trial, the hydraulic conductivity increases for MW0l and MW02 are 16.7% and 39.3% while on second trial, the percentage increases for MW01 and MW02 are 54.3% and 11.1% respectively. Although the change for MW02 decreased for 60 minutes vibration, it can still be noted as there is a positive impact of vibration to the K value and further extensive data collection will be able to provide better assessment. Thus, it has been proven that the vibration method can be effective in reducing the soil clogging effect and also able to improve the hydraulic conductivity of the soil.

Ocena możliwości zrzutu zasolonych wód poeksploatacyjnych do wyeksploatowanych odwiertów

W artykule omówiono zagadnienia zrzutu zasolonych wód poeksploatacyjnych do porowatych warstw chłonnych o niskim ciśnieniu złożowym – z zastosowaniem pompy lub bez niej. Podano warunki, jakie musi spełniać warstwa chłonna, oraz klasyfikację odwiertów zrzutowych według amerykańskiej Agencji Ochrony Środowiska (EPA) ze względu na ochronę wód pitnych. Zasygnalizowano, jakie warunki musi spełniać solanka wprowadzana do ośrodka porowatego, w tym dotyczące jej składu chemicznego, zawartości ciał stałych, obecności bakterii oraz zawartości olejów i tłuszczów. Podano sposoby określenia przepuszczalności warstwy o niskim ciśnieniu złożowym, z której brak jest samoczynnego wypływu i lustro cieczy stabilizuje się na pewnej głębokości poniżej poziomu terenu, w tym omówiono metodę tzw. slug test oraz metodę INiG – PIB opracowaną przez autorów. Podano warunki techniczne, których spełnienie wymagane jest do prawidłowego przeprowadzenia slug testu. Omówiono wady i zalety poszczególnych metod określania przepuszczalności w odwiertach, w których nie ma produkcji samoczynnej, oraz sposoby interpretacji wyników, jak również podkreślono prostotę interpretacji metodą INiG – PIB w porównaniu z metodą slug testu, wymagającą wpasowania krzywych pomiarowych do krzywych teoretycznych. Podano sposób przybliżonej oceny objętości wody zasolonej, którą można wprowadzić do otworu „na chłonność”, to jest bez użycia pompy, przy maksymalnym ciśnieniu hydrostatycznym odpowiadającym wypełnieniu otworu solanką „do wierzchu”, oraz objętości, którą można wtłoczyć za pomocą pompy przy ciśnieniu niższym od ciśnienia szczelinowania warstwy porowatej. Podano przykład obliczeniowy.

Modeling the coseismic groundwater level increase in the Oi well, central Japan

A model for coseismic groundwater level increase is presented for understanding hydrological responses of wells to seismic waves. Three types of coseismic groundwater level changes were observed in six wells 300–500 m in depth, operated by the Hot Spring Research Institute of Kanagawa Prefecture, central Japan. The first change was a sustained increase uniquely appearing at the Oi well. The second, a sustained decrease observed at most wells following the 2011 off the Pacific Coast of Tohoku Earthquake, and the third was an oscillatory response appearing in all six wells. In this study, we focused on the first response at the Oi well. We analyzed digital data at 1-Hz sampling rate of 12 events including shallow and deep earthquakes, and local to remote earthquakes from 2011 to 2016. There were 11 earthquakes which generated a sustained increase in the groundwater level in the Oi well from 5 to 10 cm. The time series of the sustained increase in the Oi well was well approximated by the decaying exponential function, characterized by a time constant ranging from 156 to 363 s. The slug test model for radial flow adequately represents the time curves observed in the Oi well, for which possible values of specific storage and hydraulic conductivity were used. The success of the application of the slug test model indicates a sudden increase in pore-pressure in the aquifer surrounding the well during the passage of seismic waves. We examined several candidates for the cause of the earthquake-triggered pore-pressure increase around the Oi well. We found that the poroelastic static strain change due to earthquake is not suitable for the sustained groundwater level increase at the Oi well. Qualitative examination suggests that following three models possibly explain the observed buildup times at the Oi well, but that all of them are not definitive: (a) permeability change due to barrier removal on the fracture surface, (b) undrained consolidation, and (c) gas bubble nucleation and growth.

Comparison of slug test methods to determine conductivity of Holocen aquifer, Dan Phuong area

Two different slug test methods including: i) slug test using the standard slug rod and ii) pneumatic slug test are conducted in different well/depth in Danphuong field site for a comparative analysis. These methods are examined at least 3 times for each well to estimate hydraulic conductivities by using Hvorslev. The results show correlation between two slug test methods is very hight with R2 = 0,93. Slug tests methods have several advantages and also disadvantage compare to each other. Practical considerations of performing the tests in real life settings are also considered in the method comparison. The slug-rod method meets 7/10 criterions while pneumatic slug test satisfy 8/10 criterions.

Sunjoto Shape Factor under Full Penetration Slug Test

Sunjoto developed shape factor equations in order to determine the drawdown and hydraulic conductivity value. Many researchers had conducted research using these equations under the pump test. Moreover, most of the research used Sunjoto equations as the comparison with the other pump test equations. Since 1951, shape factor equations have been developed to determine hydraulic conductivity value under slug test which mainly focus on the dimension of well. Afterwards, many scientists and researchers developed shape factor equations including Sunjoto, Bouwer and Rice. Therefore, this research intends to use Sunjoto equation under the slug test. The comparison of hydraulic conductivity by constant head test and slug test has been conducted in this research. The comparison value is acceptable although there are difference values that were caused by disturb and Un-disturb sample.

Assessment of groundwater resources potential using geoelectrical method and slug test in Tegal District, Central Java Province, Indonesia

Water resources are essential to support everyone in the world, and one of its sources is groundwater. Many areas in Indonesia rely on groundwater to meet their daily needs due to the lack of surface water resources. However, not all-districts have detail information about groundwater resources such as in Tegal District, Central Java Province, Indonesia. Land use planning without the support of information on water resources will cause many problems. Therefore, this study aims to assess groundwater resources in Tegal District using the geoelectrical method and slug test. The research was conducted by geoelectrical survey in 8 locations, measuring groundwater level from the nearest point, and two slug tests. The result of the survey shows that five types of materials in the area are clay, silt, sand, breccia, and lava. The sand layer is an aquifer, and it consists of two layers. The sand layer has a permeability of 6.68 m d–1. However, the clay has a permeability of 1.46 × 10-3 m d–1. The moderate potential of groundwater resources with transmissivity value of more than 50 m2 d–1 lies in the middle of the district.