Type Of Seepage Research Articles

Formation Mechanism of “Large-Area Sweating” Water Seepage from Deep Mine Sandstone Pores

The groundwater in nonkarst areas can be divided into two categories: pore water and fracture water. Unlike fracture seepage, sandstone pore seepage in deep mines manifests as a large area of “sweating,” rather than an area of local “spray,” and is difficult to plug via conventional grouting methods. This study focused on pore seepage in deep mine sandstone to improve the grouting effect. Taking the deep mine sandstone in the southwest Shandong coal field, where “large-area sweating” seepage occurs, as the study object, this study examined the pore structure, petrological characteristics, physical properties, and grain sizes of the sandstone by analyzing experimental data from thin sections and scanning electron microscopy samples. The formation mechanism of the “large-area sweating” seepage was then analyzed. The range of permeability in which “large-area sweating” seepage may occur in the sandstone was discussed. The results indicate that the process of “large-area sweating” seepage in deep mine sandstone can be divided into a matrix softening stage, a matrix erosion stage, and a “large-area sweating” water seepage formation stage. According to the case analysis on the “large-area sweating” seepage in the Tangkou coal mine of the Southwest Shandong coalfield, the lower limit of permeability of the “large-area sweating” sandstone is approximately 0.25 mD. Thus, this type of seepage can occur in deep mine sandstone with a permeability of greater than 0.25 mD and affect typical mining production. The results of this study provide information about the formation mechanism of “large-area sweating” water seepage from sandstone pores and can theoretically inform the development of a new permeation grouting technique.

Effects of seepage behaviors on coal spontaneous combustion in longwall gobs: an investigation between Darcy and non-Darcy seepage

Seepage behaviors of air leakage directly affect the coal spontaneous combustion (CSC) in longwall gobs, which is usually regarded as Darcy flow, but in fact, non-linear seepage should better characterize the properties of air flow in the gobs. To address this issue, steady-state percolation tests were conducted on broken rocks with five particle sizes, and the non-Darcy permeability parameters versus porosity and particle size were obtained by binary fitting the experimental data, and then applied to an actual longwall gob. The multi-physics coupling model of CSC in longwall gobs was modified accordingly, which was then validated by comparing with on-site observation data. Numerical solving procedures based on Darcy seepage and non-Darcy seepage were developed separately to quantify the effects of these two types of seepage on the CSC. The results show that (i) the seepage tests confirm that the seepage behavior in the broken rocks is more consistent with the non-Darcy seepage; (ii) the distributions of oxygen concentration and solid temperature under the two seepage flows are relatively similar, but the high-temperature zone in the gob under non-Darcy seepage is larger and hotter; (iii) the non-Darcy permeability coefficient has a positive effect on the coal temperature rise in the gob, while the non-Darcy flow factor has almost no effect, so taking plugging measures at the working face can effectively prevent the spontaneous combustion in gobs. This work contributes to the understanding of the air seepage behavior in longwall gobs and its impact on the CSC.

Comprehensive Geophysical Investigation and Analysis of Lining Leakage for Water-Rich Rock Tunnels: A Case Study of Kaiyuan Tunnel, Jinan, China

Leakage of lining structure is one of the main geological disasters of the tunnel, which brings heavy economic losses and casualties. Aiming at the problem of lining leakage of the Kaiyuan Tunnel in Jinan, this research has carried out a geological survey, conducted statistics, and classification of the leakage situation of the Kaiyuan Tunnel. The causes and main control factors of various types of seepage are analyzed. To locate the leakage accurately, electrical resistivity tomography, transient electromagnetic method, and ground penetrating radar are used to carry out comprehensive geophysical exploration. Two catchment zones and fractured zones are determined based on the existing geological topographic maps, geological profile maps, and geological analysis results. Transient electromagnetic detection results coincide with the known fractured zones, which confirms the existence of fractured zones and defines the scope of fractured zones. Moreover, the detection results based on ground penetrating radar show that the main adverse geological conditions inlining and surrounding rock are water diversion area, hidden water diversion area and surrounding rock fragmentation area. Subsequently, three kinds of grouting material, ultra-fine cement, ordinary Portland cement, and polymer cement, were selected for seepage control of the 800–900 m and 1310–1330 m test sections for plugging treatment. The grouting effect was analyzed and evaluated based on ground penetrating radar detection and field working conditions. Especially, the grouting radar detection shows that the grouting effect of polymer cement slurry is ideal, the grout in the water conduction area is basically filled, and the lining cracking and damage have been significantly repaired and improved. This paper verifies the accuracy and good feasibility of the interpretation criteria of comprehensive geophysical detection for typical lining defects, which can be popularized and applied in relevant tunnels and underground projects.

Cold-water corals and hydrocarbon-rich seepage in Pompeia Province (Gulf of Cádiz) – living on the edge

Abstract. Azooxanthellate cold-water corals (CWCs) have a global distribution and have commonly been found in areas of active fluid seepage. The relationship between the CWCs and these fluids, however, is not well understood. This study aims to unravel the relationship between CWC development and hydrocarbon-rich seepage in Pompeia Province (Gulf of Cádiz, Atlantic Ocean). This region is comprised of mud volcanoes (MVs), coral ridges and fields of coral mounds, which are all affected by the tectonically driven seepage of hydrocarbon-rich fluids. These types of seepage, for example, focused, scattered, diffused or eruptive, is tightly controlled by a complex system of faults and diapirs. Early diagenetic carbonates from the currently active Al Gacel MV exhibit δ13C signatures down to −28.77 ‰ Vienna Pee Dee Belemnite (VPDB), which indicate biologically derived methane as the main carbon source. The same samples contain 13C-depleted lipid biomarkers diagnostic for archaea such as crocetane (δ13C down to −101.2 ‰ VPDB) and pentamethylicosane (PMI) (δ13C down to −102.9 ‰ VPDB), which is evidence of microbially mediated anaerobic oxidation of methane (AOM). This is further supported by next generation DNA sequencing data, demonstrating the presence of AOM-related microorganisms (ANMEs, archaea, sulfate-reducing bacteria) in the carbonate. Embedded corals in some of the carbonates and CWC fragments exhibit less negative δ13C values (−8.08 ‰ to −1.39 ‰ VPDB), pointing against the use of methane as the carbon source. Likewise, the absence of DNA from methane- and sulfide-oxidizing microbes in sampled coral does not support the idea of these organisms having a chemosynthetic lifestyle. In light of these findings, it appears that the CWCs benefit rather indirectly from hydrocarbon-rich seepage by using methane-derived authigenic carbonates as a substratum for colonization. At the same time, chemosynthetic organisms at active sites prevent coral dissolution and necrosis by feeding on the seeping fluids (i.e., methane, sulfate, hydrogen sulfide), allowing cold-water corals to colonize carbonates currently affected by hydrocarbon-rich seepage.

Study on Optimization of New Type of Seepage Well Structure in Sponge City

The seepage well is an indispensable part of the construction of the sponge city. It has a good “elasticity” for the city to adapt to the environmental changes and respond to natural disasters. In the face of the current decline in the groundwater level and the water logging in the city, it is urgent to study the new type of seepage well under the complex geological conditions. In this paper, the advantages and disadvantages of the current seepage well structure are analyzed, and combined with the hydro-geological conditions in the area of Feng Xi new city of xi’an, three new types of seepage wells are put forward, such as reinforced concrete filter pool + mufti glass pipe combined structure seepage well, masonry filter pool + single glass pipe combined structure seepage well and prefabricated reinforced concrete structure seepage well. The advantage, disadvantage and applicability of the well are compared, and case analysis is provided, which provides a basis for the construction of seepage wells in sponge cities.

Upward groundwater flow in boils as the dominant mechanism of salinization in deep polders, The Netherlands

As upward seepage of saline groundwater from the upper aquifer is leading to surface water salinization of deep polders in the Netherlands, we monitored the processes involved in the Noordplas Polder, a typical deep polder. Our results show three types of seepage: (1) diffuse seepage through the Holocene confining layer, (2) seepage through paleochannel belts in the Holocene layer, and (3) intense seepage via localized boils. They differ with regard to seepage flux, chloride concentration, and their location in the polder; thus, their contributions to surface water salinization also differ. Permeable, sandy paleochannel belts cut through the lower part of the Holocene layer, resulting in higher seepage fluxes than the diffuse seepage through the Holocene layer where there are no paleochannels. The average chloride concentration of paleochannel seepage is about 600 mg/l, which is sixfold higher than the average concentration of diffuse seepage. The highest seepage fluxes and chloride concentrations are found at boils, which are small vents in the Holocene layer through which groundwater preferentially discharges at high velocities. This results in upconing of deeper and more saline groundwater, which produces an average chloride concentration of 1100 mg/l. Despite the fact that seepage fluxes are difficult to measure, we were able to calculate that boils contribute more than 50% of the total chloride load entering the Noordplas Polder and they therefore form the dominant salinization pathway.

Distribution of Subsurface Hydrocarbon Seepage in Near Surface Marine Sediments

Hydrocarbon seeps in surficial marine sediments are of two types: active and passive. Active seeps occur where gas bubbles, pockmarks, or bright spots are visible on seismic profiles and where chemosynthetic communities are present in conjunction with large concentrations of migrated hydrocarbons (macroseeps). These generally occur where generation and migration of hydrocarbons from source rocks are ongoing today (at maximum burial) or where significant migration pathways have developed from recent tectonic activity. Passive seeps occur where concentrations of migrated hydrocarbons are usually low (microseeps) with few or no geophysical anomalies. These occur typically in areas where generation and expulsion is relict (no longer at maximum burial) or regional seals prevent significant vertical migration. The type of seepage controls the distribution of migrated hydrocarbons in the near-surface sediments and should dictate the sampling equipment and approach used to detect seeps. Active seeps are usually detected near the water-sediment interface, in the water column or at the sea surface, and at relatively large distances from major leak points. Most conventional sediment and water samplers can capture active seeps. The Gulf of Mexico, Santa Barbara Channel, and parts of the North Sea have active hydrocarbon seeps. Passive seeps can only be detected relatively far below the water-sediment interface and require samples to be collected near leak points. Sampling equipment must penetrate the zone of maximum disturbance or any shallow migration barriers. In areas where surficial sediments are coarse grained or compacted, conventional gravity corers will not work. Other options for subsurface sampling include vibracores, jet cores, and rotary cores. Precise location of samples (site-specific) using seismic profiles to locate leak points is critical to detect passive hydrocarbon seeps. The Beaufort and Bering seas, offshore Alaska, and parts of the North Sea contain passive seeps.