Unconsolidated Materials Research Articles

Review and Analysis: Successful Use of Soil Tunnels in Medieval and Modern Warfare and Smuggling

For more than 2500 years, soil tunnels have been used in warfare and smuggling. Initially tunnels were utilized to attack fortresses that were underlain by unconsolidated (non-bedrock) soil materials. Later tunnels provided housing and served as smuggling corridors. The medieval warfare undermining technique involved digging soil tunnels with wooden or beam props to hold up the soil ceilings. Then flammable material, such as hay or straw, was put in the tunnel and set on fire. The fire burnt the support beams which collapsed the soil tunnel ceilings and undermined the overlying perimeter wall. Later gunpowder and dynamite replaced fire when attempting to collapse a tunnel, fortress or perimeter defense. Modern warfare soil tunnels were the pathways used to move troops, weapons and supplies to the other side of a border or wall for surprise attacks. Most of the soil tunnels were placed in easy-to-dig unconsolidated soil materials that had a low water table and were not subject to flooding. Eventually, machinery was used to drill through bedrock permitting deeper and longer tunnels for troop movement or smuggling. However, when drilling through bedrock under international borders, the process creates both noise and vibrations which were often detected by the enemy. Once discovered the tunnels were often collapsed by blowing up the tunnel, injection of gas, filling with water or wastewater, or inserting barriers. A series of case studies will be examined with the goal of determining soil and site criteria required to permit successful tunneling. The most restrictive soil and geologic conditions will be identified as well as potential mitigation methods used to overcome the site restrictions will be documented. Countries with warfare or smuggling issues along their borders, such as Israel and United States, need to identify the sections of the border most likely to be undermined by soil tunnels. In the case of Israel their entire border is susceptible as a result of the favorable arid climate, soils and geology. The US border with Mexico can become vulnerable wherever a new wall is created. Without a wall there is usually no need for soil tunnels. The US Department of Homeland Security and border patrol will need to monitor the noise and vibrations, just like the Israel does, to identify future soil tunnel locations. Eventually most of 3200 km border will have a wall that will become the target of more soil tunnels for smuggling goods and people from Mexico into the United States.

Landslide investigation using electrical resistivity tomography (ERT) technique at the location of water channel PLTM Lambangan, Pagimana, Central Sulawesi

Mass movement phenomena that occur in the research area affect the destruction of water channel in the area of PLTM Lambangan that located at the location. This research aimed to investigate soil movement phenomena in order to determine control factors that causing soil prone to move, especially in the surface geological aspect and underground lithology condition in the research area. Investigation method applied is by underground geologic and geophysical surveys using electrical method, that is Electrical Resistivity Tomography (ERT) with Wenner Configuration. Results of investigation show that geological factors are quite related to the soil movement. Movement phenomena occur in the surface with hilly to steep cut topography (21-55%) with material sourced from alluviation of clastic sediment dan carbonatic rocks. The damaged area is people farming area where fibre root of plant adds water absorption capacity of the soil. Also, sliding materials show water seepage that indicates that the moving slope has been saturated. This condition supported by information from geoelectric survey which indicates that in general the under surface material potent to slide or move because of unconsolidated material with its resistivity values in the order of 16 – 43 m that estimated related to alluvial or saturated residual soil.

NON-DARCY FLOW EVALUATION OF UNCONSOLIDATED POROUS MEDIA IN A CLOSED LOOP PERMEAMETER

A new closed loop permeameter was implemented in this work to study the fluid flow through two different unconsolidated porous media. An apparent permeability, similar to that proposed by Barree and Conway, was described in this work in terms of the absolute permeability combined with a new fluid property description, the inertial contribution factor that accounts for the domain of viscous and inertial forces. Such approach discriminate those properties of the rock as intrinsic permeability from those related to the fluid as the inertial contribution factor. The apparent permeability equation of Barree and Conway was applied to different intervals of the experimental data in which it was possible to obtain the Forchheimer coefficients as well as the inertial contribution factors according to each interval. Two different types of unconsolidated porous media materials were utilized in the new Closed Loop Permeameter, sand (1-2 mm) and glass spheres (3.96 mm). The equation of Barree and Conway provided a great agreement fitting the experimental data in a wide non-Darcy Reynolds number range. It was observed an increase in the Forchheimer coefficient and decrease in the apparent permeability with the flow rate increase. The results indicate a correlation between the permeability and the inertial effects in the non-Darcy turbulent regions in which the porous media materials with low permeability values are probably more subjected to flow losses due to the inertial effects.

A thermomechanical breakage model for shock-loaded granular media

A constitutive model is developed for dry granular materials that smoothly transitions across a wide range of pressures and temperatures. This model handles large deformations and is thermomechanically consistent. Ideas from critical-state soil mechanics, which model granular media at relatively low pressure via a breakage model, are combined with an equation of state for shock-loaded solids to investigate the compaction of initially unconsolidated brittle granular materials. The resulting constitutive equations provide a fully-coupled model containing a natural transition between granular and solid states through the Helmholtz free energy. The model is calibrated to data with a wide range of pressures and strain rates for Ottawa sand and silica and predictions of the model are compared with static compaction, penetration, and shock-loading results. The difference in Hugoniot temperatures between this calibrated model and a “snow-plow” model are negligible for pressures greater than 8 GPa; well below incipient melting.

Sediment Supply and Hydrogeological Hazard in the Quebrada De Humahuaca (Province of Jujuy, Northwestern Argentina)—Rio Huasamayo and Tilcara Area

This paper describes the hydrogeological hazard in a reach of Quebrada de Humahuaca, (Upper Valley of Rio Grande de Jujuy, in the Argentine Andes), elected a World Heritage Site by UNESCO in 2003. Along the Quebrada, the Rio Huasamayo, flowing into the Rio Grande, formed a large alluvial fan where the village of Tilcara was built. The final reach of Rio Huasamayo is an artificial channel, embanked by unconsolidated material removed from the riverbed. The village is located in an area at a lower elevation with respect to the riverbed, still in aggradation; so it is affected by an evident hydrogeological hazard. The main cause of the riverbed aggradation is the enormous sediment supply from the slopes of the Rio Huasamayo basin. The aim of the paper is to estimate the soil loss on the slopes and the consequent sediment supply to the main stream, identifying the areas of the basin mostly affected by erosion processes that cause the aggradation of the Rio Huasamayo riverbed. In this case, due to the lack of hydrometeorological stations (monitoring rainfalls, temperature, flow rates, etc.), soil loss and sediment supply to the main stream cannot be estimated through the application of commonly used models in the literature (e.g., USLE, RUSLE, USPED). Here the Gavrilovic method (EPM) was applied in combination with the data of the CORINE Project, allowing the estimation of the volume of material exiting from the catchment. So the main supplying areas (sub-basins of the Rio Huasamayo) can be identified where focused interventions for the control of solid transport could be realized, to mitigate the process of riverbed aggradation.

Effects of riparian plant roots on the unconsolidated bank stability of meandering channels in the Tarim River, China

Meandering channels with highly sinuous and distorted bends have developed along the middle and lower reaches of the Tarim River in northwestern China. Riverbanks composed of unconsolidated materials have much lower bank strengths and are susceptible to fluvial erosion and bank collapse, particularly under high flow conditions. Thus, the formation and development of meander bends in such environments appear unintuitive. It is logical to speculate that riparian plant roots in unconsolidated banks have significant effects on bank stability and bend development in the absence of cohesive sediments, but this has not been verified. To determine the influence of root cohesion on the bank stability of meandering channels in the Tarim River, in situ measurements and sampling of roots from locally dominant riparian vegetation, i.e., Populus euphratica (PE), Tamarix ramosissima (TR), and Phragmites australis (PA), were conducted on the meandering bends to obtain root parameters, including diameter and root area ratio. The radius of curvature of local bends corresponding to sampling sites was also calculated using remote sensing imagery. We used the Bank Stability and Toe Erosion Model (BSTEM) to quantitatively estimate the effects of different root conditions on channel bank strength. The results confirmed that roots (and sand–root composites) provide effective reinforcement to unconsolidated banks, control the bank erosion, and hence enhance bank stability. However, the effects were highly variable under different root conditions. PA roots generally improved bank strength more than those of PE or TR, with PA, PE, and TR improving bank strength by 88.2%, 73.2%, and 63.6%, respectively. Riparian vegetation in this extremely arid and unconsolidated sediment environment therefore appears to be a prerequisite for sustaining the meandering channel.

Icelandic Pit Chains as Planetary Analogs: Using Morphologic Measurements of Pit Chains to Determine Regolith Thickness

AbstractPit chains are distinctive geologic landforms present on planetary bodies across the solar system, which can be used to understand regolith properties and formation. If there is a direct relationship between pit diameter and the regolith depth, pit chains can be used to map regolith thickness across a planetary surface. Here, the morphology of individual pits within pit chains in northern Iceland was measured as a planetary analog to determine whether there is a direct relationship between individual pit diameters and pit depth, which is assumed to be a proxy for regolith depth. The morphology of pit chains and regolith thickness was measured in three different locations in northern Iceland, within two different substrates: unconsolidated floodplain sediments and more consolidated soils overlaying basaltic lava flows. There is a significant linear relationship between pit diameter and depth for pit chains located in the floodplain sediment, but not for pits located in basaltic materials. However, this depth‐diameter relationship does not correlate with regolith thickness. The depth of the pits in basaltic materials is more representative of the regolith depth than the pits in the floodplain sediments. If high‐resolution topography data are available, then the depth of pits in more consolidated materials can be used as a reliable estimate of regolith thickness. In more unconsolidated materials, the pit depth represents a minimum regolith depth. This ability to resolve regolith thicknesses may help resolve the processes by which regolith is emplaced and has implications for the thermal evolution of planetary bodies.

Controlling factors of microclimate in blocky surface layers of two nearby relict rock glaciers (Niedere Tauern Range, Austria)

ABSTRACTCoarse blocky material is known to have a ground cooling effect compared to other types of unconsolidated surface material, which may have an influence on spatial distribution and conservation of permafrost. In the light of climate warming, this effect may retard permafrost degradation or exert prolonged ground cooling in general. To contribute to a better understanding of this ground cooling effect and potential influencing factors, the thermal regime of blocky surface layers of two comparable nearby relict rock glaciers with opposing aspects was investigated. Air, surface and shallow ground temperature at 1 m depth were continuously measured over a four-year period at nine locations distributed over two rock glaciers. The blocky surface layer of the SW-exposed rock glacier exhibits lower and more heterogeneous temperatures than the NE-oriented despite a higher potential solar radiation. The data suggest a thinner or more discontinuous seasonal snow cover at the SW-exposed rock glacier, causing a more efficient winter cooling. The importance of air flow driven heat transfer as a source of cooling is supported by the data. Results illustrate thermal heterogeneities within blocky layers and the importance of the seasonal snow cover pattern in addition to topography and microclimatic variability in high relief terrain is hypothesized.

Characterization and environmental impact assessment of gold mine tailings in arid regions: A case study of Barramiya gold mine area, Eastern Desert, Egypt

Geochemical and mineralogical characterization and environmental impact assessment were performed on Barramiya gold mine tailings, Eastern Desert, Egypt. The Barramiya gold mine is situated within ophiolite-decorated Nugrus suture zone, which composed of dismembered sequence of highly deformed and metamorphosed mafic to ultramafic rocks and their hydrothermal alteration products (carbonate rocks), interbedded with meta-volcano clastic rocks of the Nubian Shield. Morphometric parameters were quantified using ArcGIS 10.0 with Shuttle Radar Topography Mission (SRTM) maps. A total of four tailings samples were gathered and analysed by XRF, XRD, ICP-OES/MS and ESEM. Tailings are characterized by homogeneous silty fine sand, high carbonates in the form of dolomite and ankerite, and low sulfides content in the form of arsenopyrite and pyrite relics. High concentration averages of heavy elements are found for As (2936 mg/kg), Cr (237 mg/kg), Sr (219 mg/kg), Ni (150 mg/kg), V (131 mg/kg), Zn (64 mg/kg), Cu (51 mg/kg), Co (19 mg/kg) and Pb (12 mg/kg). They reflect mafic and ultramafic rocks, graphite schists, and quartz veins of the study area. Gypsum is present as secondary phase, identified in the shrinkage crack fillings. Morphometric drainage basin parameters for wadi Barramiya basin show rectangular to subdendritic drainage pattern with a moderate hazard degree. This study recommends designing multiple-layered dry cover, overlain by plant cover at uppermost part for treatment of the gold mine tailings; otherwise, wind and water erosion can easily remove all dissolved and unconsolidated material that absorb heavy elements and would create a potential risk to the surrounding ecosystem.

ASSESSMENT AND REMEDIATION OF A LIGHT NON-AQUEOUS PHASE LIQUID HYDROCARBON PLUME IN FRACTURED BEDROCK

INTRODUCTION During the extension of an access road on the Canadian Forces Base (CFB) Esquimalt in Colwood, British Columbia, a black, viscous, liquid hydrocarbon product was observed oozing from newly exposed bedrock fractures in the roadside. Road excavation was subsequently halted to undertake assessment and remediation of the hydrocarbon product. The exposed bedrock was dammed with sawdust, a geomembrane barrier was installed and the area was backfilled until an appropriate course of action could be determined. The site location is shown in Figure 1. The property boundary and key site features are shown in Figure 2; the hydrocarbon seep is shown in Figure 3. Bunker C oil is a heavy-end (high molecular weight) hydrocarbon product that has a specific gravity slightly less than water and is therefore a light non-aqueous phase liquid (LNAPL). The source of the LNAPL was inferred to originate from a decommissioned fuel depot located approximately 100 m distance uphill from the road, where 40,000 barrels of Bunker C fuel oil were historically stored in one of three, large above-ground storage tanks (ASTs). A Bunker C oil spill reportedly took place at the tank farm more than two decades prior; however, the spill volume was unknown and initial investigations found no evidence of contamination between the roadside LNAPL occurrence and the former AST. Furthermore, there was also anecdotal evidence that an historic asphalt manufacturing facility may have operated in the vicinity of the access road. A hydrocarbon product similar to Bunker C is used in the manufacture of asphalt. The source and extent of the LNAPL and the potential migration pathways to the roadside location were therefore unknown. When an LNAPL spill occurs in the subsurface, the LNAPL can migrate downward under gravity through the soil pore space in the unsaturated zone. When LNAPL encounters the ground water table (the top of the saturated zone), it tends to spread out laterally because it is less dense than water and will migrate primarily in the direction of the water table gradient (water table slope). However, when LNAPL encounters bedrock, the direction of LNAPL migration can become much more complicated depending on the degree and orientation of bedrock fractures that control its movement. When fracture density is sufficiently high and the fractures are interconnected, contamination is able to migrate down-gradient through the bedrock in the same manner as through unconsolidated materials. However, when dominant structural features are prevalent that favour specific orientations, preferential pathways are created that can result in the cross-gradient migration of LNAPL. This paper presents a case study for the assessment and remediation of LNAPL in bedrock at the Canadian Forces Base (CFB) Esquimalt (the site). Geological mapping of bedrock structural features has long been used by the mining industry to identify key structures associated with economic zones of mineralization and to predict the location and extent of mineralized targets. In a similar regard, to effectively remediate LNAPL within fractured bedrock requires the identification and characterization of any structural features that might be controlling the preferential migration of LNAPL within the subsurface to other areas of the site. A significant amount of surface outcrop is present at the site and this was recognized as a cost-effective opportunity to complete a geological assessment of the bedrock. A geological mapping program was subsequently undertaken to assess bedrock outcrops for fracture density, fracture aperture, the orientation of primary fracture sets and lithologic contacts. The area was also inspected for larger scale structural features such as faults, deformation and erosional features that might influence contaminant migration. Fracture sets and lithologic contacts were mapped by outcrop location, and fractures with visible LNAPL were mapped separately from those without LNAPL. The geological data collected was used to construct stereographic projections of structural planes on a stereonet. Poles to structural planes were plotted and colour-coded by area and by presence/absence of LNAPL. The plots were then analyzed individually, and as a composite plot, to identify the dominant preferential pathways controlling LNAPL migration at the site. By superimposing these features on areas where LNAPL was observed, LNAPL delineation targets were effectively identified and the plume was subsequently delineated with confidence and remediated.

Local structural and geomorphological controls on landsliding at the Leigu restraining bend of the Beichuan-Yingxiu fault system during the 2008 Mw 7.9 Wenchuan earthquake

The 2008 Mw 7.9 Wenchuan, China, earthquake produced many damaging landslides in the Longmenshan region along the eastern margin of the Tibetan Plateau, China. Among the thousands of reported landslides, some are geologically notable because of their close spatial relationship to local fault rupture complexities. The Leigu landslide is particularly interesting because it formed at a restraining bend along the Beichuan-Yingxiu fault system in a structural position that favored hill-slope collapse because of a variety of preexisting structural and geomorphological conditions. The 2008 landslide reactivated an older landslide that is indicated by a preserved paleo-scarp upslope from the main 2008 event scarp. Our field and analytical results coupled with a review of existing geological information on the region indicate that the landslide site is located between two regional folds with opposing plunge directions and that the restraining bend is the displacement transfer zone between two parallel, but offset segments of the Beichuan-Yingxui Fault system. In addition, NE-oriented steep joints were reactivated as slip surfaces in the upper slopes of the landslide area within an anticline hinge zone that focuses vertical uplift. Steep valley walls due to incision of the antecedent Laochangkou River and abundant rainfall during the earthquake period, combined with intense seismic acceleration were contributing factors to the landslide event. During the earthquake, approximately equal components of strike-slip and SE-directed thrusting occurred on surface ruptures within the bend, offsetting older landslide deposits and man-made structures. Field results indicate that sliding was facilitated by loose unconsolidated materials from the previous landslide that were remobilized above a soft, low-friction basal slip surface. The Leigu landslide provides an important case study for evaluating potential landslide hazards close to active fault systems where complex 3-D structural geometries and high-relief, steep terrain combine to generate significant ground instability during large magnitude earthquakes.

Hydraulic Conductivity of Sandy Soil with Varying Grain Size

A concept of mean particle size and size factor is presented in this paper and an attempt is made to relate the hydraulic conductivity to mean particle size, taking into account the optimum moisture content and maximum dry density. The distribution of particle size has a significant effect on hydraulic conductivity. It is possible to determine the mean particle size and size factor from the gradation curve. For the purpose of experimental analysis, three samples of soils were collected, local river sand available in market, coarse sand1.18mm sieve and quarry dust. For determining the hydraulic conductivity a constant head permeability test is conducted. A few exact conditions to compute water powered conductivity utilizing grain estimate dispersion of unconsolidated spring materials have been assessed in this examination. Evaluating examination of soil tests extricated from the test openings during ground water examination venture was performed to decide their arrangement and molecule measure dispersion attributes, from which pressure driven conductivities were figured. In particular, every single exact equation are to be utilized carefully inside the space of appropriateness

Observations of the atmospheric electric field preceding intense rainfall events in the Dolomite Alps near Cortina d’Ampezzo, Italy

Debris flow events, generated by surface runoff, occur with great frequency in the Dolomites (Northeastern Italian Alps) during the summer season. Summer thunderstorms, which are common in the region, can quickly generate runoff at the base of rocky cliffs, which then entrains and propagates downstream the underlying unconsolidated material. In the past, the main atmospheric feature considered in evaluating the initiation of debris flow events was rainfall. Observations led to the development of rainfall intensity–duration thresholds for sediment mobilization, which compared incoming severe rainfalls with the potential for triggering debris flows. This study works toward the examination of another characteristic of the atmosphere, the atmospheric electric field. In particular, the behavior of the electric field prior to convective rainfall is investigated as an indicator of rainfall intensities capable of triggering debris flows, in a basin near Cortina d’Ampezzo (Italy). Results suggest that prior to bursts of intense rainfall, the electric field derivative frequency distribution exhibits a recurrent pattern roughly half the time. When it occurs, the amplitude of derivative frequency distribution intersects the zero axis twice before rainfall reaches maximum intensity. A regression model is designed which considers the amplitude maximum and the difference in time between the crossings of the zero axis. The validation of this model suggests a mild relationship between electric field and rainfall intensity in an alpine environment.

Hydrothermal eruptions at unstable crater lakes: Insights from the Boiling Lake, Dominica, Lesser Antilles

The Boiling Lake - a major touristic attraction in the Morne Trois Pitons National Park, Dominica's (West Indies) World Heritage site - is located in an area of high hydrothermal activity in the southern part of the island. This spectacular lake is characterized by unstable behavior which has been interpreted to result from the presence of a water body above a fluctuating gas-filled, or multi-phase vent system. The system produces a near-boiling lake that occasionally drains and refills with water, without any simple periodicity. Despite the fact that such unstable draining lakes are thought to be non-eruptive, the Boiling Lake is known to have sourced occasional small hydrothermal eruptions as well as toxic gas emissions which accompany the refilling phase of these drainage events. Similar explosive events seem also to be likely after landslide slumped rocks from steep altered crater walls cover the vent area in the lake leading to overpressurized conditions. In both cases, rock expulsion and gas release continue to pose serious threats for tourists and tour guides. While conceptual models exist describing possible mechanisms of the Boiling Lake drainage itself, little information exists to date regarding the trigger mechanisms related to the explosive events. Further, no estimation of the eruption processes and dynamics of these events has previously been attempted. To address this knowledge gap, we employ here a combined field- and laboratory-based approach in order to i) characterize the properties of the dominant lithologies from the crater walls at Boiling Lake, ii) determine how the ongoing alteration may affect their petrophysical properties (e.g., porosity and permeability), and iii) evaluate how water-saturated, unconsolidated wall rock materials behave when rapidly decompressed from a slightly elevated pressure and temperature conditions.Here, we propose that it is the petrophysical state of the materials involved (e.g. porosity, permeability and alteration-related strength) which controls the style and energy of these eruptions, as well as the potential for landslides from the crater walls. The experimentally simulated scenarios included in this study are: i) decompression from only slightly elevated pressure conditions inferred for small hydrothermal eruptions occurring after lake drainage events, and ii) decompression from rapidly enhanced pressure conditions produced by the capping and overpressurization of the vent area following landslide episodes. Ejection velocities obtained from rapid decompression experiments were used as input parameters for ballistic trajectory calculations, allowing for estimation of the potential area impacted by ejected debris.We anticipate that this study will serve as a contribution to the understanding of the hazard potential of future hydrothermal eruptions at unstable crater lakes in general, as well as providing direct insights into the ongoing hydrothermal activity at the Boiling Lake.

Geotechnical engineering evaluation of soil utilizing 2D multichannel analysis of surface waves (MASW) technique in New Akhmim city, Sohag, Upper Egypt

New Akhmim is one of the recent cities in Sohag Governorate which was proposed by Egyptian New Urban Communities Authority (ENUCA) to build new communities overcoming the overpopulation problems. The main objectives of this research are delineating the shallow subsurface structures and lithology of the foundation layers and evaluating their geotechnical characteristics. For calculating shear-wave velocity (VS) in the studied site, sixteen MASW sections were carried out using Geometric strata visor-NZ 48 channels with vertical geophones of 4.5 Hz and inter-geophone spacing of 3 m. The recorded data were analyzed using the SurfSeis software to evaluate the degree of soil compaction or rock consolidation and foundation stability based on seismic wave velocity and density.The proposed site contains two engineering subsurface layers; the first one is the upper most layer and consists of intercalations of unconsolidated material (gravels and sands) of different shear wave velocities. The second layer (compacted shale) is more compact with higher velocity (bedrock). Elastic moduli and geotechnical parameters of the first and the second layers in the eastern part is more competent than the western part. The degree of competence of the second layer is higher than that of the first one, therefore it is considered as more qualified for engineering purpose and constructions design. Precautions should be taken into consideration for the geotechnical engineering problems e.g. swelling or contraction possibly resulting from the second shale layer.

Characterization of Cementation Factor of Unconsolidated Granular Materials Through Time Domain Reflectometry with Variable Saturated Conditions.

The cementation factor is necessary to determine porosity via the Archie equation, and its range of values has been suggested in many previous studies. However, the cementation factors in the literature are limited to fully saturated conditions, and it may thus be inaccurate to use the same value in other saturation conditions. The objective of this study is to characterize how the cementation factor varies depending on the saturation percentage. In this study, glass beads and soil are selected as the specimens, and two relative density values, 40% and 80%, are selected. Time domain reflectometry (TDR) is used to obtain both the saturation and electrical resistivity of the specimens. TDR is installed in the cell, and fluid is continuously circulated from the bottom to the top of the porous material for 30 min. The estimated saturation increases with time and the electrical resistivity is reduced during the circulation. Finally, the cementation factor at every saturated stage is determined, and the error ratio based on the porosity is calculated to show the importance of the cementation factor. The results show that there is a high error ratio when an unsuitable cementation factor that does not consider the saturation condition is used. This study demonstrates that the method for determining the actual cementation factor using TDR and the Archie equation can be applied in various saturation conditions.

Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

Lunar regolith thickness deduced from concentric craters in the CE-5 landing area

Lunar regolith is the layer of fragmented and unconsolidated rock material that is repeatedly stirred and overturned on the lunar surface. It can provide critical information about lunar geologic processes (e.g., impact, volcanism) and the space environment. China's Chang'E-5 (CE-5) mission, which will be launched in 2019, will land on the lunar near-side surface and return at least 2 kg of lunar regolith through surface collection and by boring a hole no <2 m in depth. This study focuses on the depth of lunar regolith in the planned CE-5 landing area, which may be important for sampling activity and related scientific research. The traditional crater morphological method uses the dimensions of particular craters to derive the lunar regolith thickness, i.e., the lunar regolith thickness is estimated through the characterization of concentric, flat bottomed, and central mound craters. However, recent studies show that flat bottomed and central mound craters can also be formed by clustered projectiles. Therefore, only concentric craters were used to estimate the lunar regolith depth in this study, and subsequent morphological analysis indeed indicates that flat bottomed and central mound craters were primarily formed from secondary clustered impacts in this area. The precise locations and sizes of the selected concentric craters were determined from a high-resolution seamless Digital Orthophoto Map (DOM) of the CE-5 landing area, which was generated by our team using 765 selected LROC NAC images. All the concentric craters, including the inner and outer crater rims, were then mapped in the DOM. Local lunar regolith depths were derived according to the previously established relationship between lunar regolith depth and the inner and outer diameters. The results show that the lunar regolith in the area ranges from 0.74 m to 18.00 m, with a mean of 7.15 m, and is much shallower in the southeast than in other areas.

A Rapid Method for Analyzing Well Log Records in Preparation for Water Resource Mapping.

The needs of subregional and local entities for water resource management are immediate, and required information is not forthcoming in a timely and relatively inexpensive manner. The following method allows one to use all available well record data to produce baseline hydrogeologic unit maps using geographic information system querying and mapping techniques. Subjective borehole and geophysical strata descriptions are converted to objective equivalent numerical values by establishing the average hydraulic conductivity of the combined soils making up the stratum of interest. These hydraulic conductivity values are then used to assign each stratum to a hydrogeologic unit based on typical ranges of hydraulic conductivity for aquifers, aquitards and aquicludes. The resulting data are queried and mapped to provide a preliminary description of a shallow aquifer system composed of unconsolidated materials. This method can be used to provide information to make initial estimates of the configuration of the shallow aquifer system and to plan for groundwater sustainability. Two examples of maps for an area in northeastern Illinois that were prepared using the resulting database are presented.

Soil survey to support land use/land cover planning in BPS and BPM region in Gangajalghati block, West Bengal, India

To secure food and other associated need for growing population, the only way is to increase agricultural production and to utilize the land with respect to its potentiality in a sustainable way. In the present study an attempt has been made to evaluate sustainable land use/land cover planning in Buried Pediment Shallow (BPS) and Buried Pediment Medium (BPM) region in Gangajalghati block, Bankura district, India using remote sensing and GIS techniques. BPS consists of weathered and unconsolidated materials with thin soil cover (0–5 m) mainly sand mixed with silt and clay. BPM consists of gently sloping dissected topography with shallow to deep soil profile (5–20 m) which are characterised by severely eroded, coarse textured, stoniness and acidic soils. Ruggedness of the topography, scarcity of water, soil acidity (pH 5–6) and soil erosion are the key problems in this area, which hampers the productivity of the land. Hence these soils have very low moisture holding capacity and very low nutrient status. To overcome these problems, different thematic maps are taken into consideration for recommendation of land use/land cover planning in this area. This study will facilitate enhancement of agricultural productivity in a sustainable manner and restoration of ecological balance between degraded and rain fed ecosystems.