Application of Very Low Frequency (VLF) Method for Estimating Karst Underground River in Tanjungsari District

Drought is the main problem for clean water needs in Tanjungsari district. This research aims to provide information on the existence of underground river for deep well drilling. The methods used are geologic-structural analysis and application of Very Low Frequency (VLF) methods. Strike and dip measurements of 150 joints were conducted in the research area. Analysis using rosette diagram shows that the main geologic-structure orientation has a direction of Northwest - Southeast and Northeast – Southwest. Very Low Frequency (VLF) acquisition was measured across the possible occurrence of subsurface water flow directions predicted from geologic-structural analysis. The length of the VLF acquisition line is 2500 meters with 30 m spacing and 108 points acquisitions. The direction of VLF line is N 2700 E. The result shows that there are 2 locations that have high conductivity values, appearing at 1800 meters and 2200 meters. The results of this structural and VLF analyses indicate the existence of underground river at the location of 454326 N, 9105870 E.

Structures and Settlement Control of Yujingshan High-Speed Railway Tunnel Crossing Massive Rockfill in a Giant Karst Cave

The Yujingshan high-speed railway tunnel crosses a giant cavern system with a 108 × 104 m3 volume chamber and an 18 km long underground river. The massive project, which lasted three years, was eventually awarded the “Overcoming the Challenges” award by the International Tunneling and Underground Space Association (ITA) in 2020. However, since the cave chamber was filled with large-scale rockfill, structural settlement is a non-negligible problem. This paper presents the unique structures of a bridge supporting railway tracks wrapped by tunnel lining and the settlement control of the Yujingshan tunnel crossing massive rockfill in the giant cave. The geological characteristics and design considerations are systematically introduced. A three-dimensional coupling discrete element method (DEM) and finite difference method (FDM) numerical model and 13 months of long-term settlement monitoring were conducted to evaluate the settlement behavior. The results indicate that the morphology of cavern and internal deposits caused the whole rockfill to migrate to the lower left. The tunnel structure consequently developed a significant inclined settlement. The continuous construction load would increase the settlement value by 31.4%. The bottom reinforcement of steel-pipe pile with grouting could effectively inhibit settlement and differential settlement. Considering the simulation results, the tunnel bottom had greater settlement than the limit standard for high-speed railway embankment, which means this special structure form is reasonable for operation. Meanwhile, the monitoring results show that the tunnel bottom settlement in D3K279+891~D3K279+947 had not performed an apparent convergence trend after 13 months. Further structural monitoring and compensation grouting should be actively considered for operation maintenance.

Analysis of Community Perception on the Impact of Sand Mining in Mujur River and Regoyo River

Sand mining is an activity of exploiting natural resources below the surface of the ground that can be carried out underground river flows to extract minerals, namely sand. Sand mining is generally carried out to increase development. This activity has a positive impact on the community. However, if you ignore the environmental impact analysis, it will harm the community, which can cause environmental damage. Therefore, this study aims to analyze public perceptions of the impact of sand mining on the Mujur River and the Regoyo River. The research method used is a survey and data obtained by conducting observations, documentation, and questionnaires. Respondents in this study amounted to 30 people who are the surrounding community. For one month, this research was conducted around the Mujur River and the Regoyo River, Pasirian District, Lumajang Regency, East Java. The data of this study were analyzed using descriptive analysis. This study indicates the high public perception of the impact of sand mining on the Mujur River and Regoyo River, seen from the percentage of the questionnaire calculation, which is divided based on the positive and negative impacts of sand mining on the Mujur River and Regoyo River.

ARCHITECTURAL AND PLANNING ORGANIZATION OF SERVICE OBJECTS LOCATED ON TRANSPORT HUBS

The article discusses the main aspects of the architectural and planning organization of service facilities for transport hubs. The main blocks of the functional planning structure of transport interchange hubs (T.I.HUB), elements of their structure and principles of placement in the structure of large cities have been formed in the center, in the structure of residential areas, in historical city centers, and in the contact zone of urban and suburban development. The work substantiates the relevance of the development regarding the design of transport hubs (T.HUB)s in the structure of modern cities, which are constantly and systematically developing, increasing the need for the transportation of an increasing number of passengers. The dynamic development of modern infrastructural cities, especially large ones, require a revision of the norms and dimensions of transfer stations, the landing front of stops, the reorganization of the inner spaces of the transport hubs (T.HUB), etc. The design and construction of transport hubs can be carried out in a completely new construction, reconstruction or reconstruction with modernization, or in the difficult conditions. Already today, many big cities are suffering from traffic jams bordering on collapse, especially during peak hours. Therefore, this problem must be solved in all possible ways, especially attention should be paid to the architectural and planning organization of service facilities, which are located at the transport hub (T.HUB). A transport interchange hub is a nodal element of the city's planning structure, which allows organizational transfer of passengers between various types of urban and external (intercity, international) passenger transport or between different lines of the same type of transport in an urban structure. For example, transport hubs (T.HUB) are possible in the structure of the functioning of a railway transport hub from one railway line to another. Transport interchange hubs (T.I.HUB)can be specialized or multifunctional, and include a number of facilities for passing passenger services and social infrastructure: accumulative lobbies in front of the entrance group ("entrance" - "exit"), a foyer with digital validation of electronic tickets and cards on different routes of passengers; cargo and goods rooms for baggage claim (at airports, river stations and railway stations); customs premises (if we are talking about international flights departing from transport hubs (T.HUB); intercepting parking lots and taxi and bus stands; public service facilities; shops, catering establishments; financial institutions, etc. As noted earlier, we can talk about six types of transport hubs (T.HUB) in the structure of the designed and existing nodes on land, underground, river, rail, sea and air transport. Thus, modern transport hubs can be organized not only in the city structure, but also in ports, railways. railway stations and airports, which can significantly expand their typological range of service facilities.

Source, Partition and Ecological Risk of Polycyclic Aromatic Hydrocarbons in Karst Underground River Environment, Southern China

As the main source of drinking water in the karst areas of southern China, underground rivers play an important supporting role in local economic and social development. However, due to the special aquifer structure in the karst areas of southern China, polycyclic aromatic hydrocarbons (PAHs) can easily enter the water environment of underground rivers and cause serious pollution, which will affect the water quality safety. In this study, Qing-shui Spring underground river in Nanning city was selected as a representative of the typical underground river in southern China, and the pollution characteristics, source analysis, ecological risk assessment and diffusion law of PAHs were studied. The results showed that the total concentration of PAHs in groundwater and surface sediments was in the range of 282.42–464.88 ng/L and 400.14–1194.69 ng/g, respectively, and the overall concentrations of PAHs were below the moderate pollution level. Pollutant discharge and physical and chemical properties of PAHs caused the concentrations of PAHs to decrease gradually from upstream to downstream, but the proportion of high-cyclic PAHs increased gradually. According to the source analysis results of the ratio method, PAHs sources in groundwater were mainly biomass combustion sources in the upstream, oil sources in the middle and mixed sources in the downstream. Sediment and groundwater had some differences. The middle and upper reaches were the source of biomass combustion, while the middle and lower reaches were the mixed source. The ecological risk assessment results showed that the ecological risk of groundwater was at a moderate level, while the ecological risk of sediment was at a low level. Benzo[a]anthracene (BaA) and benzo[b]fluoranthene (BbF) in groundwater and acenaphthylene (Acy) and fluoranthene (Flu) in sediment should be monitored intensively. Appropriate control measures should be put in place to prevent further pollution. Partition coefficients varied from 0.73 to 3.85 L/g in the sediment–water interface, increasing with the rise of PAH compounds. All of the organic carbon partition coefficients (Koc) in the sediment–water interface were higher than predicate values based on the typical model of equilibrium distribution; this indicated that PAHs were strongly adsorbed in the sediment. The linear free energy relationship coefficient between the Koc value and the n-octanol-water partition coefficient (Kow) was 0.85 but the slope was lower than 1, indicating that sediment in the Qing-shui Spring underground river had weak lipophilic characteristics and adsorption ability for PAHs. The results can provide a reference for the risk assessment and pollution control of PAHs in the karst underground rivers in South China.

Karst Geology in Southwest Hubei and Mitigation of Geohazards During Mountain Tunnel Through a Large Karst Cave

The outcrop area of carbonate rocks accounts for 61.6% of the total area in Southwest Hubei. The action of tectonic application, erosion of surface and underground water system, topography, and carbonate geology leads to the formation of large karst caves, and their features are as following: considerably large, long and narrow, winding and in different forms. Limited by route directions, large karst caves would be encountered during tunneling through mountains, therefore causing hazards such as instability of the karst cave, water or stone ingress, damage to the tunnel, and long-term instability. A case study of mountain tunnel through a large karst cave is presented. The large karst cave is formed due to the erosion of limestone by two underground river systems. The length, width and volume of the cavity of the large karst cave are about 139 m, 91 m and 4.3×105 m3. The large karst cave is overall stable without strong external factors. Engineering proposals and treatment of the large karst cave are introduced. The small pipe grouting method is used to treat the foundation. Two kinds of lining structure schemes are adopted, double lining open-cut tunnel structure, and traditional tunnel structure after backfill. The water outside the lining of the open-cut tunnel is introduced into the tunnel ditch and discharged through the tunnel drainage system. Monitoring and measurement during tunneling construction and operation process are introduced.

Hydrogeology of Mangsri Cave, Gunungsewu Karst Area, Java Island, Indonesia

The Gunungsewu karst area is not only known for its unique landscape but also its recurring drought events. To meet the water supply, the local population utilizes several water potentials, namely doline pond, spring, and underground river. This study was designed to analyze the hydrogeological conditions of Mbangsri Cave, following its accidental discovery by the community at the end of 2018. The hydrogeological analysis was conducted by geological surveys, which consisted of rocks collection and structural measurements, cave mapping, and recharge area delineation based on remote sensing images acquired by unmanned aerial vehicles. The results showed that Mbangsri Cave, in the hydrogeological perspective, had low water resources potential. It is believed to be the result of (1) relatively small catchment area, (2) a fault in the southern part of Mbangsri Cave, creating a small groundwater basin, and (3) the thin epikarst layer, limiting the water storage.

First record of Cercyon (s. str.) inquinatus Wollaston, 1854 from Turkey with notes about this problematic species (Coleoptera: Hydrophilidae: Sphaeridiinae: Megasternini)

Cercyon (s. str.) inquinatus Wollaston, 1854 is recorded for the first time from Turkey. It was found in the darkest part of a vast cave occupied by an underground river and pools. The specimens were collected, in or near water, without being sure that they are aquatic and subterranean. Bright and black or blackish body, pronotum with a slight partial and median groove, rather convex interstries, male genitalia are quite characteristic. The habitat and sampling methods are described. The difficulty of identifying the insect with existing keys is exposed and analyzed. Photos of Turkish specimen and a list of the associated fauna are provided.