Bedrock outcropping in the accumulation zone of the largest glacier in Mexico(Glaciar Norte of Citlaltépetl),as evidence of a possible accelerated extinction

The highest volcano in Mexico,at the same time the third largest mountain in North America(Citlaltépetl,5610 m a.s.l.),is home to the largest glacier in the country.Because of the extinction of the Popocatépetl glacier(5500 m a.s.l.)caused by eruptive activity,and the almost disappearance of the Iztaccíhuatl glaciers(5220 m a.s.l.)due to the lower elevation of the mountain,the Glaciar Norte of Citlatépetl has been the only glacier that has shown a certain degree of stability as a response to the altitude in which it is located.However,as occurs in almost all glaciers on the planet,the retreat of its glacier terminus has been continuous.Furthermore,during the last years the thickness of its upper part began to decrease rapidly until its bedrock was exposed for the first time in 2019.Due to its ecosystem importance and because it is the main glacier in Mexico,as well as the only one in the world located at latitude 19°N,in this work its current dimensions are updated,as well as the local climatology that governs the current state of the glacier is pointed out.The study was based on the analysis of high-resolution Sentinel-2 optical images,as well as through Sentinel-1 SAR images,with the support of climatological information from the study area.Therefore,the outcropping of the bedrock in the accumulation zone and the consequent horizontal retreat of the upper part of the glacier are documented;at the same time,the decrease in the thickness of the ice along it is noted.The rocky outcrop in the accumulation zone suggests that the flow dynamics of the ice towards the ablation zone will be considerably less,accelerating the retreat of the glacier terminus.Finally,the ascent of the glacial front to 5102 m a.s.l.and the modelled altitude of the equilibrium line to 5276 m a.s.l.are reported as a warning signal in terms of snow catchment and mass balance;likewise,the decrease of 23%of its surface is also indicated regarding the surface reduction monitoring that has been done until 2017.These findings may indicate that the future of this glacier is related to its possible extinction sooner than previously thought,with severe environmental consequences,especially in terms of the provision of drinking water for thousands of inhabitants of the slopes of the volcano.This research is expected to help reflect on the impacts of current climate variability and at the same time serve as a reference for the tropical glaciers on the planet.

Salt-Lake Basin Bedrock Weathered Crust Gas Reservoir in the Altun Mountains Front of the Qaidam Basin,Western China

The bedrock weathered crust in front of the Altun Mountains in the Qaidam Basin,western China,is different from others because this is a salt-lake basin,where saline water fluid infiltrates and is deposited in the overlying strata.A large amount of gypsum infills the bedrock weathered crust,and this has changed the pore structure.Using core observation,polarized light microscopy,electron probe,physical property analysis and field emission scanning electron microscopy experiments,the characteristics of the weathered bedrock have been studied.There are cracks and a small number of dissolved pores in the interior of the weathered crust.Matrix micropores are widely developed,especially the various matrix cracks formed by tectonics and weathering,as well as the stress characteristics of small dissolved pores,and physical properties such as porosity and permeability.This‘dual structure’developed in the bedrock is important for guiding the exploration of the lake basin bedrock for natural gas.

Geochemistry of Cretaceous Sea Rocks from the LEO-3X Well in the Eastern Abidjan Margin, Côte d’Ivoire Offshore Basin

In this study, we apply geochemical and statistical analyses to evaluate the source rocks and kerogen type of Cretaceous sediments from the Cote d’Ivoire sedimentary basin. The geochemical analysis includes pyrolysis data such as total organic carbon (TOC%), generation source potential (S2) and hydrogen index (HI). The results of the cluster analysis separated the source rocks in the study area into two main groups. 1) Source rocks characterized by HI > 300 (mg/g), TOC from 1.76% to 3.19% by weight, and S2 from 6.55 to 14.46 (mg/g), indicating good to excellent source rocks with type II kerogen and are capable of generating oil. 2) Source rocks characterized by HI between 200 and 300 (mg/g), TOC from 1.6 to 2.02 wt%, and S2 from 3.45 to 5.36 (mg/g) indicating medium to good source rocks with type II-III kerogen and capable of generating a mixture of oil and gas.

厚冲积层薄基岩条件下采动井稳孔工艺与应用

以平煤股份八矿煤层气采动井01井为研究对象,借助钻井窥视仪获取了不同层位的套管变形破坏特征,分析了导致套管变形的主要影响因素。在此基础上,设计了基于“抗、让、防”稳孔工艺的井身结构和稳孔措施,并对同一井场的05井应用。结果表明,同产气周期下,基于稳孔工艺设计的采动井套管完整度高、变形小、产气量稳定。此稳孔工艺可为相似地质条件下的采动井井身结构设计提供经验参考。

Physics-informed optimization for a data-driven approach in landslide susceptibility evaluation

Landslide susceptibility mapping is an integral part of geological hazard analysis.Recently,the emphasis of many studies has been on data-driven models,notably those derived from machine learning,owing to their aptitude for tackling complex non-linear problems.However,the prevailing models often disregard qualitative research,leading to limited interpretability and mistakes in extracting negative samples,i.e.inaccurate non-landslide samples.In this study,Scoops 3D(a three-dimensional slope stability analysis tool)was utilized to conduct a qualitative assessment of slope stability in the Yunyang section of the Three Gorges Reservoir area.The depth of the bedrock was predicted utilizing a Convolutional Neural Network(CNN),incorporating local boreholes and building on the insights from prior research.The Random Forest(RF)algorithm was subsequently used to execute a data-driven landslide susceptibility analysis.The proposed methodology demonstrated a notable increase of 29.25%in the evaluation metric,the area under the receiver operating characteristic curve(ROC-AUC),outperforming the prevailing benchmark model.Furthermore,the landslide susceptibility map generated by the proposed model demonstrated superior interpretability.This result not only validates the effectiveness of amalgamating mathematical and mechanistic insights for such analyses,but it also carries substantial academic and practical implications.

HVSR analysis of pumice sands for sediment depth characterization:A case study for Guadalajara,Mexico

The horizontal to vertical spectral ratio(HVSR)methodology is used here to characterize pumice soils and to image the three-dimensional surface geometry of Guadalajara,Mexico.Similar to other Latin American cities,Guadalajara is exposed to high seismic risk,with the particularity of being the largest urban settlement in Latin America built on pumice soils.Methodology has not yet been tested to characterize subsoil depths in pumice sands.Due to the questionable use of traditional geotechnical tests for the analysis of pumice soils,HVSR provides an alternative for its characterization without altering its fragile and porous structure.In this work,resonance frequency(F0)and peak amplitude(A0)are used to constrain the depth of the major impedance contrast that represents the interface between bedrock and pumice soil.Results were compared with borehole depths and other available geotechnical and geophysical data and show good agreement.One of the profiles estimated on the riverbanks that cross the city,reveals different subsoil thickness that could have an impact on different site responses on riverine areas to an eventual earthquake.Government and academic efforts are combined in this work to characterize depth sediments,an important parameter that impacts the regulations for construction in the city.

Mechanisms to explain soil liquefaction triggering,development,and persistence during an earthquake

Mechanisms have been proposed to explain the triggering,development,and persistence of soil liquefaction.The mechanism explaining the horizontal failure plane(triggering)and its depth below the phreatic surface is governed by the flux properties and effective stress at that plane.At the failure plane,the pore water pressure was higher than the effective stress,and the volume change was the highest.The pore water pressure is a function of the soil profile features(particularly the phreatic zone width)and bedrock motion(horizontal acceleration).The volume change at the failure plane is a function of the intrinsic permeability of the soil and bedrock displacement.The failure plane was predicted to occur during the oscillation with the highest amplitude,disregarding further bedrock motion,which was consistent with low seismic energy densities.Two mechanisms were proposed to explain the persistence of soil liquefaction.The first is the existence of low-permeability layers in the depth range in which the failure planes are predicted to occur.The other allows for the persistence and development of soil liquefaction;it is consistent with homogeneous soils and requires water inflow from bedrock water springs.The latter explains many of the features of soil liquefaction observed during earthquakes,namely,surficial effects,“instant”liquefaction,and the occurrence of short-and long-term changes in the level of the phreatic surfaces.This model(hypothesis),the relationship between the flux characteristics and loss of soil shear strength,provides self-consistent constraints on the depth below the phreatic surfaces where the failure planes are observed(expected to occur).It requires further experimental and observational evidence.Similar reasoning can be used to explain other saturated soil phenomena.

Quantitative Evaluation of Heavy Metal Pollution and Its Influencing Factors in Water Bodies of Karst Areas

At present, there is relatively little research on the synergistic effects of heavy metals in soil, sediment, and bedrock on heavy metal pollution in water bodies. In this paper, heavy metals in soil, sediment, bedrock, and water of a typical karst watershed in southwest China were investigated. The results indicated that the average values of heavy metals in soil and sediment were relatively higher than those in bedrock except for Ni and As. During the research period, As and Cd were the main heavy metal elements polluting the soil and sediment in the study area, while water bodies were mainly polluted by Ni, As, and Cd. The pollution assessment indicated that there were instances of poor or very poor water quality in the study area during the study period;the soil as a whole was slightly polluted by Cd and As;sediment was subject to moderate Cd pollution and mild As pollution. Analysis of geochemical form for heavy metals showed that heavy metals in soil and sediment were mainly in residual form, and the proportions of exchangeable As and Cd were relatively high. Multiple statistical analysis showed that heavy metals in sediment, soil, and bedrock explained 23.8%, 16.8%, and 16.2% of the changes in heavy metals of water, respectively. The research results can provide scientific basis for the prevention and control of heavy metal pollution in water bodies.

梁北二井主副井基岩段水害注浆治理技术

基于梁北二井主副井基岩段水害特点,提出工作面帷幕预注浆加壁后注浆的水害注浆治理方案,采用理论分析和数值计算的方法,给出工作面预注浆方案和井壁壁后注浆方案设计,并进行了实践,取得了良好的治理效果。

超深水基岩潜山储层分布式光纤温度试井方法

超深水永乐X区潜山气藏具有储层非均质强、纵向岩性组合多样的特征,传统生产测井技术在落实储层产出特征时存在局限性。采用分布式光纤测温技术测试获得了YL1井产能测试生产层段的温度数据,结合渗流力学和流体力学理论,建立了气藏渗流和井筒管流温度—压力场双耦合模型,计算了气井产出剖面变化引起的温度响应特征。采用Levenberg Marquart(LM)反演算法实现了YL1气井产出剖面定量解释分析。研究结果表明,气井多层测试时高渗层对应井筒温度下降斜率大,温度变化速度快,温降大,通过温度剖面可以作为判断高渗地层、裂缝或非产层产出贡献;利用建立的分布式光纤温度产出剖面解释方法,定量评价获得了砂砾质风化带、风化裂缝带和内幕裂缝带产出贡献,解释结果与录井气测率具有正相关性,且与地质认识吻合,证明了解释理论的可靠性。研究结果对分布式光纤温度监测多层气藏产出剖面技术的推广具有重要理论及应用价值。

Breaking mechanism and control technology of sandstone straight roof in thin bedrock stope

The key problem to be solved urgently is how to avoid the occurrence of support break-off and water inrush in the stoping of sandstone straight roof under the action of load transfer in unconsolidated aquifer.For this reason,taking the thin bedrock 1602(3)working face of Huainan(the middle part of Anhui Province)Panyi Coal Mine as the engineering background,this study establishes the stope mining model by using the discrete element UDEC software and the mathematics mechanical model of the support load,and analyzes the reason of support crushing and decides to re-mining the working face by using the compulsive roof caving method.It is concluded that when the working face of sandstone straight roof is broken,the"voussoir beam"structure cannot be formed and acts on the support in the form of cantilever beam,but only when it falls to the high key stratum can the"voussoir beam"structure be formed and at this point,at this time,the bracket bears the weight of the rock layer in the range from the fractured sandstone layer to the lower critical layer.The working resistance of the support increases with the increase of the thickness and the breaking length of straight sandstone roof.When the breaking length of the roof reaches a certain extreme value,the support crushing accidents will occur.Managing roof with compulsive roof caving method can reduce the intensity of rock pressure in the stope,and the working face can be safely stoped,which provides a certain reference for similar conditions.

Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical,magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins

The Makhonjwa Mountains, traditionally referred to as the Barberton Greenstone Belt, retain an iconic Paleoarchean archive against which numerical models of early earth geodynamics can be tested. We present new geologic and structural maps, geochemical plots, geo- and thermo-chronology, and geophysical data from seven silicic, mafic to ultramafic complexes separated by major shear systems across the southern Makhonjwa Mountains. All reveal signs of modern oceanic back-arc crust and subductionrelated processes. We compare the rates of processes determined from this data and balance these against plate tectonic and plume related models. Robust rates of both horizontal and vertical tectonic processes derived from the Makhonjwa Mountain complexes are similar, well within an order of magnitude, to those encountered across modern oceanic and orogenic terrains flanking Western Pacific-like subduction zones. We conclude that plate tectonics and linked plate-boundary processes were well established by 3.2-3.6 Ga. Our work provides new constraints for modellers with rates of a 'basket' of processes against which to test Paleoarchean geodynamic models over a time period close to the length of the Phanerozoic.

Classification of conditions for short-wall continuous mechanical mining in shallowly buried coal seam with thin bedrock

The room and pillar method is usually used to extract coal from shallowly buried seams with thin bedrock. This results in a very low production efficiency and in a low degree of extraction. In recent years short-wall continuous mechanical mining has been extensively used in many situations except shallowly buried coal seams with thin bedrock. The principles governing movement of the overlying strata above the 2-2 coal seam were deduced from in-situ experience, laboratory data, calculations and computer simulations. The thicknesses of the bedrock in the Shendong Coal Field where the coal is shallowly buried are classified into 5 types: <10 m, 10–15 m, 15–25 m, 25–35 m and >35 m, which was done using fuzzy clustering results. A series of reasonable, relative parameters in each category have been calculated and analyzed. One proposed way to perform short-wall continuous mechanical mining in shallowly buried coal seams is given. This is significant for coal mines with similar geological conditions.

TORSIONAL VIBRATIONS OF A RIGID CIRCULAR PLATE ON SATURATED STRATUM OVERLAYING BEDROCK

The torsional vibration of a rigid plate resting on saturated stratum overlaying bedrock has been analysed for the first time. The dynamic governing differential equations for saturated poroelastic medium are solved by employing the technology of Hankel transform. By taking into account the boundary conditions, the dual integral equations of torsional vibration of a rigid circular plate are established, which are further converted into a Fredholm integral equation of the second kind. Subsequently, the dynamic compliance coefficients of the foundation on saturated stratum, the contact shear stress under the foundation and the angular amplitude of the foundation are evaluated. Numerical results indicate that, when the dimensionless height is bigger than 5, saturated stratum overlaying bedrock can be treated as saturated half space approximately. When the dimensionless frequency is low, the permeability of the soil must be taken into account. Furthermore, when the vibration frequency is a constant, the height of the saturated stratum has a slight effect on the dimensionless contact shear stress under the foundation.

The Identification of Large-Giant Bedrock Landslides Triggered by Earthquake in the Longmenshan Tectonic Belt

The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.

Spatial distribution modeling of subsurface bedrock using a developed automated intelligence deep learning procedure:A case study in Sweden

Due to associated uncertainties,modelling the spatial distribution of depth to bedrock(DTB) is an important and challenging concern in many geo-engineering applications.The association between DTB,the safety and economy of design structures implies that generating more precise predictive models can be of vital interest.In the present study,the challenge of applying an optimally predictive threedimensional(3D) spatial DTB model for an area in Stockholm,Sweden was addressed using an automated intelligent computing design procedure.The process was developed and programmed in both C++and Python to track their performance in specified tasks and also to cover a wide variety of diffe rent internal characteristics and libraries.In comparison to the ordinary Kriging(OK) geostatistical tool,the superiority of the developed automated intelligence system was demonstrated through the analysis of confusion matrices and the ranked accuracies of different statistical errors.The re sults showed that in the absence of measured data,the intelligence models as a flexible and efficient alternative approach can account for associated uncertainties,thus creating more accurate spatial 3D models and providing an appropriate prediction at any point in the subsurface of the study area.

Fractal Character of China Bedrock Coastline

Fractal theory was applied to a preliminary discussion of the fractal character and formation mechanism of the coastline of the bedrock coast of China on the basis of GIS (Geographical Information System). Some significant conclusions were drawn:(1) The fractal dimensions of the coastline and linear structures of Liaodong Peninsula are 1.0093 and 1.0246 respectively, those of Shandong Peninsula are 1.019 and 1.021 respectively, etc.(2) The fractal dimensions of coastlines of Liaodong Peninsula, Shandong Peninsula, Zhejiang and Fujian-Guangdong tend to increase with the spatial change from north to south.(3)The regional linear structures(including faults)control the basic trends and fractal dimensions of coastlines as a whole in the regions of the bedrock coast of China:the more the controlling effect of linear structures, the smaller the fractal dimensions of coastlines.(4)The substantial constituents of coast and biologic function both play an important role in affecting the fractal dimensions of coastlines of Liaodong Peninsula, Shandong Peninsula, Zhejiang, Fujian-Guangdong and Taiwan Island.

A modified TOPMODEL introducing the bedrock surface topographic index in Huangbengliu watershed,China

Subsurface stormflow is a dominant runoff mechanism in steep humid mountainous areas.An insite measurement of subsurface stormflow suggests that the bedrock surface plays an important role in the runoff generation and routing process,which was rarely adopted in hydrological modelling studies.To improve the runoff simulation performance,the bedrock surface topographic index is introduced,and a modified TOPMODEL based on the bedrock surface topographic index is developed to simulate the runoff.The modified TOPMODEL is applied to the Huangbengliu(HBL),a steep watershed in Gongga Mountain,and proved to be more appropriate for the HBL watershed,especially for peak simulation.The Nash-Sutcliffe model efficiency(NSE)is improved from 0.24 to 0.58 in the calibration period and from 0.40 to 0.62 in the verification period.The result of this study can advance the understanding of the mechanism of flash floods and contribute flood control and disaster prevention in the HBL watershed and similar areas.

Study of the engineering geologic feature of weathering zone of bedrock in 810 producing area of Luling Mine

For a safe extracting of the mine resource of the razor thin capping rock, a study of waterproof, sand prevention, roof fall prevention must be made. As a result, it’s necessary to master the engineering feature of weathering zone of bedrock. According to the lithology appraisal and X diffract analyses, the mineral feature of weathering zone of bedrock in 810 producing area has been studied in this article. By testing the physical mechanics index of weathering zone, we have found out some features of physical mechanic quality. Utilizing the determined result of viscosity index and slaking test, we reach a conclusion of the water stability of weathering zone, that is the weathering zone rock belongs to the type that is easily slaked when encountered water and the water stability is weak.

Role of Multiple High-Capacity Irrigation Wells on a Surficial Sand and Gravel Aquifer

Within McHenry County, IL, the fastest growing county in Illinois, groundwater is used for 100% of the water needs. Concerns over water resources have prompted the investigation of the surficial sand and gravel aquifers of the county. While the eastern portion of the county is urbanizing, the western portion remains devoted to agriculture. High-capacity irrigation wells screened within the surficial sand and gravel aquifer are used for crop production. To assess the impacts of the irrigation wells on the aquifer, a groundwater flow model was developed to examine five different scenarios reflecting drought conditions and increased pumping. Results show that the surficial sand and gravel aquifer is capable of meeting current water demands even if recharge is decreased 20% and pumping is increased 20%. The additional loss of discharge and increases in pumping result in head differences throughout the aquifer.