Overburden Layer Research Articles

Nonlinear dynamic analysis of soil-pile interactions of nuclear power plants with nonlithological foundation

PurposeThe dynamic response of the nuclear power plants (NPPs) with pile foundation reinforcement have not yet been systemically investigated in detail. Thus, there is an urgent need to improve evaluation methods for nonlithological foundation reinforcements, as this issue is bound to become an unavoidable task.Design/methodology/approachA nonlinear seismic wave input method is adopted to consider both a nonlinear viscoelastic artificial boundary and the nonlinear properties of the overburden layer soil. Subsequently, the effects of certain vital parameters on the structural response are analyzed.FindingsA suitable range for the size of the overburden foundation is suggested. Then, when piles are used to reinforce the overburden foundation, the peak frequencies in the floor response spectra (FRS) in the horizontal direction becomes higher (38%). Finally, the Poisson ratio of the foundation soil has a significant influence on the FRS peak frequency in the vertical direction (reduce 35%–48%).Originality/valueThe quantifiable results are performed to demonstrate the seismic responses with respect to key design parameters, including foundational dimensions, the Poisson Ratio of the soil and the depth of the foundation. The results can help guide the development of seismic safety requirements for NPPs.

Potential Impacts of Okpuno Egbu Dumpsite on Groundwater Resources in Parts of Nnewi, Southeastern Nigeria

The study area, Nnewi is one of the most populated, commercial and industrialized cities in Anambra State. Geophysical data were collected from 15 vertical electrical sounding (VES) points and hydrogeochemical analysis of 15 groundwater samples collected from 15 locations were analyzed for their chemical composition and used to assess the impact of the dumpsite at Okpunoegbu on groundwater in the study area. The results of the vertical electrical sounding indicate that most of the aquiferous units fall within the fourth layer at most of the Relocations with an average resistivity of 1340.25Ωm, an average thickness of 41.75m and average depth of 51.25m. The range of the regional water table is from 25.41m to 99.42m. The Dar-Zarrouk parameters; longitudinal conductance and transverse resistance, s and t were determined from the geophysical data to be 0.007mho and 55966.9Ω respectively. The results of s indicate that the protective capacity of the overburden layers to underlying aquifer is low. which implies easy transmission of pollutants to the aquifers making them vulnerable to pollution. The results of water analysis show that the range of pH in the samples is between 5.73 to 6.95 indicating that 20% of the water samples are slightly acidic and 80% to alkaline. TDS, TSS and EC were found to be within the permissible limits of WHO and NSDWQ standard guidelines. COD and BOD were above the permissible limits indicating the water samples to be severely polluted. DO1 and DO5 range between 22.78 - 65.40 mg/L and 48-358.96 mg/L respectively. The major cations and anions were within the permissible limits.. However, the heavy metals range in samples were cadmium (0.04-0.37mg/L), chromium (0.01-0.10mg/L), mercury (0-0-07mg/L) and lead (0.1-0.93mg/L), exceed the permissible limits in some samples. The geospatial distribution maps of the heavy metals implicate the dumpsite and other sources as contributors of the increased concentrations of cadmium and lead. while indicating the dump as a major contributor of chromium and mercury to groundwater in the study area. The calculated quality indices, WQI and HMPI rate the groundwater as highly polluted and unsuitable for drinking, and the CD and HMEI as moderately to highly polluted, respectively. The identified hydrochemical facies classify the water as Ca-Cl and Ca-Mg –Cl – SO4 water type. The Cl – SO4 facie indicate end water usually with increased age found in the discharge areas. The Okpunoegbu dumpsite is an important source of groundwater contaminants and pollutants especially the heavy metals such as cadmium, mercury, chromium and lead. The protective capacity of the overburden is enhancing the vulnerability of the aquifers to pollution as they are rated as low. It is recommended that some remediation measures be carried out to restore the groundwater quality and prevent further pollution being initiated and appropriate water treatment be carried before use for drinking purposes.

Assessment of seismic landslide susceptibility of bedrock and overburden layer slope based on shaking table tests

The landslide susceptibility assessment (LSA) of bedrock and overburden layer slopes subjected to earthquake action remains a challenging issue. In this study, an LSA method was proposed for the seismic design of slope engineering. First, a frequency response function was used to identify the vibration characteristics of the slope based on signal processing. The characteristic factors and assessment process of the LSA are then proposed. Based on the similarity principle, the method was applied to three groups of shaking table tests with different overburden thicknesses. The results show that with the increase of the thickness of the overburden layer, the landslide susceptibility of the bedrock and overburden layer slope increases, and the critical amplitude of the seismic landslide continuously decreases. The seismic LSA indexes of the model tests calculated by the proposed method show better robustness than those calculated by the transfer coefficient method. Through linear fitting, the critical amplitude of the seismic landslide was predicted more accurately. A limitation of this method is that multiple acceleration-measuring data points are required for earthquakes and the excitation data must be stable. The feasibility of this method need to be verified for complex multistructured slopes in the future.

Prediction of the seismic behavior and backfilling scheme optimization of immersed tunnel based on the ruyifang project

The backfill soil is the first line of defense that ensures immersed tunnel's safety and stability, but its seismic performance has not been investigated in previous studies. This study employs the Ruyifang tunnel as its research object to determine the most dangerous cross-section. It establishes a two-dimensional soil-structure interaction system for complex sites to evaluate immersed tunnels' safety during earthquakes, clarify the structural failure mechanism, and optimize the backfilling scheme. In addition, this study investigates the tunnel element's response, damage, and stress under static and dynamic loads and obtains the impact of backfilling materials by considering plastic damage in structures, soil viscoelastic properties, and various backfilling schemes. The results showed that the tunnel section's stress has prominently distributed characteristics. Moreover, the structure exhibits tensile failure during ground motions, and the bottom of the side wall is the critical area. The inertial force is the primary factor affecting the seismic capacity at the overburden layer and flanks, while stiffness plays a vital role at the cushion. These dynamic properties and related backfilling technology can provide technical support for the anti-seismic design of immersed tunnels.

Shaking Table Test on Dynamic Damage Characteristics of Bedrock and Overburden Layer Slopes

Abstract This article performs groups of shaking table tests to study the dynamic damage characteristics of the slope that is composed with inclined bedrock, upper overburden soil layer, and weak soil interlayer. The prototype is of the entrance slope of the Mount Zheduo tunnel, which is located in the mountains of the western Sichuan Plateau in China. The test model is designed based on the similarity theory. The peak ground acceleration (PGA) amplification coefficient, Fourier transform, and transfer function theory are employed to analyze the test results. The results before slope failure indicate that the PGA amplification coefficient of both the overburden layer and the weak interlayer increases as the excitation intensity increases. At the same time, the dynamic response of weak interlayer is amplified on low-frequency wave excitation while that is impaired when high-frequency seismic waves dominate. When the slope is damaged, the slope undergoes large shear deformation: the whole overburden layer slides along the weak interlayer, and the PGA amplification coefficient of the weak interlayer sharply decreases. The frequency response function indicates that the vibration relationship between the upper part of the weak interlayer and the slope surface is very close, and the slope surface vibration may be mainly affected by the vibration in the upper part of the weak interlayer, which reflects the early predictability in the failure symptoms of the slope.

Impact of Solidified Municipal Sludge as Temporary Covering Soil on the Stability of Landfill Slope

Solidified municipal sludge is widely used as temporary covering soil in landfill. Due to the complex leachate of landfill, solidified municipal sludge has the problems of stagnant water and strength degradation. In order to investigate the influence of solidified municipal sludge on the stability of landfills, a landfill slope model with SEEP/W and SLPOE/W was established, using the actual infiltration as the boundary condition. Based on the changes in permeability and strength of the intermediate overburden layer, the migration law of leachate in a landfill under the condition of an intermediate overburden layer was analyzed. The relationship between landfill slope safety, climatic conditions and deterioration of the intermediate overburden layer was further explored. The results show that the permeability of the intermediate overburden layer affects the distribution of leachate and the height of stagnant water. During the rainstorm period, the safety factor of the landfill slope decreased rapidly from 1.4 to 1.0 or even lower. With the decrease in the shear strength of the intermediate overburden, the safety factor of the landfill slope was reduced to less than 1.0. Therefore, maintaining the permeability and strength of solidified municipal sludge at a certain level is required to ensure the safety and stability of landfill slopes.

Geophysical Investigation of Part of Ahmadu Bello University Farm, Nigeria

Geophysical methods are becoming an increasingly valuable tool even for agricultural applications. Agricultural geophysics investigations are commonly focused on delineating small- and/or large-scale objects/features within the soil profile (````````~ 0 to 2 m depth) over very large areas. The study was carried out at a farm site in Ahmadu Bello University, to delineate subsurface structures with depth. It revealed the lithological units in the study area. The analyses has revealed various lithological units from the results of the inverted sections along the profiles. The study area has shown clearly two distinct layers, overburden and weathered basement. The overburden layer is clayey sand, sandy clay, and laterite. This laterite soil show very high resistivity anomaly that may be referred to as consolidated laterite. The weathered layer which contains medium grained sand with clay and feldspar materials also has the presence of fractured part that could act as the aquifer in the area. From the subsurface properties, this farm land may have low agricultural yield or may limit the cultivation potential of the region, but the region may be good for underground water yield.

PRE- FOUNDATION STUDIES USING VERTICAL ELECTRICAL SOUNDING AND SOIL SAMPLE ANALYSIS

Subsurface rock properties investigation to categories foundation competent layer for the proposed engineered structure capable of housing offices, lecture halls, and laboratories was carried out using geophysical (GPHY) and geotechnical (GTECH) techniques. Electrical resistivity GPHY technique using vertical electrical sounding (VES) field procedure was utilized in which nineteen (19) VES spots were occupied. Results of the VES revealed 2-D subsurface geoelectric sequences comprising of incompetent overburden layer of about 5 m thick with resistivity value between 10 and 210 ohm-m typical of clay soil material. Beneath this layer are sand formation and fresh bedrock with resistivity range of 750 to 1000 ohmm, which are good formations for foundation. Additionally, according to GPHY studies, western and northern portions of the region are marked by fractures/faults, which could cause building subsidence if foundation is stationed at these points. The results of the analyses of the soil samples taken in five different points in the study area revealed: (1) grain size distribution with 0.075 mm particle size passing of an average of 41% signifying the occurrence of clay, corroborating the presence of clay material within the weathered layer in GPHY investigations; (2) active and expansive nature of the soil with linear shrinkage greater than 8% revealing unsuitability of topsoil for foundation; (3) medium plasticity of soil indicating possible soil swelling; and (4) concomitant GTECH and GPHY results of the topsoil and weathered layer properties. The overburden layer with clayey materials must be removed and areas with geological structures must be taken into account.

Evaluation of groundwater repositories in parts of Enugu, Eastern Nigeria via electrical resistivity technique

Resistivity survey was carried out in Enugu North, Southeastern Nigeria, in order to evaluate the groundwater condition of the area. The inadequacy of surface water, proper knowledge of the aquifer and increasing population has affected the extraction and development of groundwater in the area. Resistivity, thickness, depth, curve frequencies and protection level were determined. The result revealed a total of 5–6 geoelectric layers with model curves exhibiting the following curve types: KHK taking about 10%; AAKQ, KHAK, KHAA, HKQ, HKQQ and HAA taking 12%, AAA, AKH, HAK and KHKQ taking 24% while AKQ and AAK take 20 and 34%, respectively. The aquifer is within the fourth and fifth layer considering the layer with the largest thickness with the fourth layer taking up to 84% of the aquifers in the study area. The overburden layer resistivity and thickness ranged from 589.8 to 85,094.8 Ωm and 8.9 to 99.5 m with mean values of 42,642.3 Ωm and 54.2 m, respectively. The contour maps were generated using Surfer software package version 15 which show the variation of overburden parameters. The study area was generally considered as having a high protective level as a result of the low values of geophysically based protection index of the aquifer layers and weak to fair GPI rating implying that the aquifer can be protected from infiltrating contaminants. However, high hydraulic conductivity and porosity suggest high groundwater potential and high infiltration of polluted geofluids.

PENGGUNAAN UJI F UNTUK MENGETAHUI SIGNIFIKAN HUBUNGAN ANTARA PRODUKSI PENGUPASAN LAPISAN OVERBURDEN DAN LOSS TIME SERTA MENENTUKAN STANDARD ERRORNYA

This research was conducted at PT. Starindo Sakti Award for 31 days. This study aims to determine whether or not there is a significant relationship between overburden stripping production and loss time. Because stripping of overburden is an activity that affects mining activities, the researcher is interested in analyzing every mining activity, especially in stripping the overburden layer at the mining front at PT. Starindo Sakti Award using a Kobelco SK-200 excavator. To determine whether or not the relationship between overburden stripping production and loss time is significant, the F test can be carried out. find out the deviation of the data. After conducting the F test, it turns out that the relationship between overburden stripping production and loss time is significant (very influential), as evidenced by the results Fhitung of 686 and Ftabel of 3.34 with a standard error of 5,8.

Dynamic response of drill string when sonic drilling rig is applied to blasting hole operation

Sonic drilling technology has the advantages of high efficiency and good stratum adaptability, which is suitable for geophysical blasting hole drilling. The longitudinal vibration transmission law of drilling tools is not clear, which limits the improvement of drilling efficiency and drilling depth, resulting in low drilling speed of geophysical blasting holes. In this study, a longitudinal vibration model of sonic drill string considering vibration head and stratum coupling boundary is established. Through numerical simulation, the transfer law of longitudinal vibration between overburden layers and the drill string was obtained. The larger the elastic coefficient of the stratum is, the larger the resonance frequency of the sonic system is, and it plays a slight role in promoting the transmission of sound waves. The larger the damping coefficient of the stratum, the smaller the amplitude of the sonic system, but the resonance frequency is basically unchanged. There is a tiny new resonance due to frequency superposition. The results show that the changes of elastic coefficient and damping coefficient caused by stratum changes inevitably affect the vibration response of the drill string system. The model provides a theoretical basis for the vibration transmission law of drill string when a sonic drilling rig is used for geophysical blasting in the overburden layers. Reasonable selection of drilling parameters can improve drilling performance.

SUBSTANTIATION OF BULLDOZER-EXCAVATOR-AUTOMOBILE COMPLEX FOR REMOVAL OF OVERBURDEN LAYER OF FLUVIOGLACIAL DEPOSITS IN THE CONDITIONS OF SOSNIVSKY GRANITE DEPOSIT

Purpose and task. The aim of the research is to substantiate the expediency and efficiency of using a bulldozer-excavator-automobile complex with the use of ripper bulldozers to remove the overburden layer of fluvioglacial deposits in the conditions of the Sosnivsky granite deposit. To achieve this goal, it is necessary to: establish the patterns of distribution and features of fluvioglacial deposits; to analyze possible technological schemes of development of gravel and sand deposits; justify the need and effectiveness of the technological complex of equipment for the removal of fluvioglacial deposits in the quarry; to establish the dependence of the variable productivity of the excavator on the average size of the piece of rock. Research methods. An integrated approach was used to solve the set tasks: analysis and generalization of previous research on the peculiarities of fluvioglacial deposits and the possibility of using equipment complexes for the development of gravel and sand mountains; technological substantiation of the offered engineering and scientific decisions; analytical calculation of variable productivity of the excavator depending on the average size of a piece of rock. Scientific novelty. The possibility of using a bulldozer-excavator-automobile complex of equipment for removing the overburden layer of fluvioglacial deposits in rock quarries has been substantiated. The analytical dependence of the change in excavator productivity on the average piece size of fluvioglacial deposits is obtained. Conclusions and practical significance. It is established that when the average size of gravel-sand material changes from 20 to 200 mm, the productivity of the excavator decreases by 1,59 times. It is proved that the productivity of the excavator type "straight shovel" is 17% higher than the productivity of the backhoe excavator. For the conditions of the Sosnivsky granite deposit quarry, where the weighted average size of a piece of fluvioglacial sediment is 171 mm, the variable productivity of the excavator is: according to the first technological scheme (hydraulic backhoe excavator placed on the roof of the sediment) – 474,1 m3/shift; according to the second technological scheme (excavator "straight shovel" is located on the lower production horizon) – 553,1 m3/shift. Keywords: fluvioglacial deposits, quarry, technological schemes, equipment complex, excavator productivity, gravel-sand rocks.

Sensitivity Analysis of Influencing Factors of Underground Civil Air Defense Construction Vibration under Vehicle Load

Grey correlation theory is an uncertainty analysis method, which can find the relevance of various factors studied through certain data processing in incomplete information and find the main influencing factors. In order to study the influence of vehicle load on the vibration of underground civil air defense construction, taking the civil air defense construction at the intersection of Zhongzhou Middle Road and Shachang South Road in Luoyang as the study subject, based on the field measured data, and using ANSYS to expand the working conditions, this paper studies the influence of such factors as elastic modulus of concrete, thickness of overburden layer, density of soil layer, elastic modulus of soil layer, vehicle speed, and vehicle mass on the vibration of the civil air defense construction through the grey correlation sensitivity analysis method. The field measurement and numerical simulation results show that the displacement, velocity, and acceleration values decrease gradually from the mid−span position of the roof to the wall. Displacement, velocity, and acceleration are important indexes for evaluating vibration. The grey correlation degree of the influencing factors of displacement and velocity from large to small is density of soil layer, vehicle mass, vehicle speed, elastic modulus of concrete, elastic modulus of soil layer, and thickness of overburden layer. The grey correlation degree of the influencing factors of acceleration from large to small is vehicle mass, layer of density of soil layer, vehicle speed, elastic modulus of concrete, elastic modulus of soil layer, and thickness of overburden layer. The grey correlation degree of soil layer density, vehicle mass and vehicle speed to displacement, velocity, and acceleration is 0.7951–0.9993, which indicates that their influence is significant. This study can provide reference for the design and construction of similar civil air defense constructions.

ANALISIS PEMBENTUKAN TANAH DARI BATUAN PENUTUP OVERBURDEN PADA AREA REKLAMASI PT BORNEO INDOBARA GUNA MENDUKUNG KEBERHASILAN REKLAMASI SECARA BERKELANJUTAN

This study aims to analyze the process of soil formation on overburden material in the reclamation area in 2013 (9 years), 2015 (7 years), and 2018 (4 years) to support the success of sustainable reclamation, and analyze the relationship between planting age, morphology and climate conditions in the study area that can affect the process of soil formation in the overburden. The research was conducted at a coal mining company located in Tanah Bumbu Regency, South Kalimantan Province. The research method used was descriptive quantitative. Data collection was done by making a test trench and taking soil profile data which includes topsoil thickness, intermediate layer, and overburden. Soil texture, soil color, and data on roots that penetrated the soil were also recorded and analyzed. The results of the test trench analysis showed that the process of soil formation in the overburden began to occur in the reclamation area in the 9th year (2013). The indicator found lateral roots in the soil layer at a depth of 40-60 cm which is an overburden layer with gray soil color. The correlation test showed a strong relationship between soil acidity (pH) and the year of planting (r2 = 0,74). The relationship between organic C elements and the year of planting (r2 = 0,68). The element N in the soil has a very strong relationship with the year of planting (r2 = 0,92). The next element was P2O5 in the soil having a moderate relationship (r2 = 0,46) and K2O elements had a strong relationship (r2 = 0,75). The results of soil chemical analysis and also soil texture showed that the soil fertility status at the study site was in low condition. This study concluded that the process of soil formation in overburden was found in the planting year area of 2013 or year 9, with indicators such as the appearance of roots in the overburden area at a depth of 20 - 40 cm, whereas in 2015 and 2018 no roots were found in the overburden. Climatic and morphological conditions accelerated the process of soil formation in the overburden because this very wet condition accelerated the process of leaching nutrients to the surface layer of the reclamation area. The process of weathering in the soil, especially in overburden, will cause plant roots to enter the overburden layer by bringing nutrients produced by trees, undergrowth, and litter to the research area.

Damage evolution mechanism of rock-soil mass of bedrock and overburden layer slopes based on shaking table test

Damage evolution mechanism of rock-soil mass of bedrock and overburden layer slopes based on shaking table test

Nonlinear numerical simulation of dynamic response of pile site and pile foundation under earthquake

AbstractTo study the influence of the nonlinear connection of pile and soil on the dynamic response characteristics of the pile foundation, this article proposes to study the dynamic response of the bridge pile foundation to the slope by combining the centrifugal shaking table test and OPENSEES open source finite element program. This article introduces the pressure-dependent multiyield surface model based on confining pressure. Through the inverse calculation of the similarity ratio of the centrifuge model test, the OPENSEES two-dimensional nonlinear finite element model of the pile group in the slope section can be established. The centrifuge shaking table test is to input the preset seismic wave horizontally at the bottom of the model box. The form of seismic wave is El Centro wave verification of two-dimensional finite element model of the pile group in slope section under earthquake. The reliability of the model is verified by comparing the test and calculated values of dynamic response (residual horizontal displacement and final bending moment) of the pile body under five different peak acceleration seismic wave loading conditions. In the dynamic response experiment of slope pile foundation, in the embedded part below the bedrock surface, the residual horizontal displacement of each pile body is zero. Constrained by the cap beam and tie beam, the displacement of the free section of the pile group at these two positions is basically the same. Through comprehensive analysis, the displacement of P1 and P2 piles is basically the same. The calculated value of the final bending moment of P1 and P2 piles shows the same change trend as the test value, and the test value is slightly larger than the calculated value. The relative errors of the maximum final bending moment of P1 pile under each loading condition are 7.4, 7.8, 12.6, 3.9, and 9.6%, respectively, and the relative errors of P2 pile are 4.6, 3.6, 12.5, 13.6, and 11.5%, respectively. The analysis relative error is caused by the elastic element used in the calculation of the pile body, which is different from the mechanical behavior of the simulated pile body material in the test. Dynamic response of slope site according to the existing centrifuge test results can be seen that the deformation at the slope shoulder of slope site is the most obvious under the earthquake. The inclined interface of soft and hard rock and soil layer will aggravate the dynamic response of the overburden layer on the slope, weakening its ability of seismic energy consumption.

Electrical resistivity structure of Danau Ranau geothermal prospect area based on integrated 3-D Inversion of impedance tensor and tipper vector

Subsurface electrical resistivity distribution needs to be revealed to explore the geothermal potential in The Danau Ranau prospect area, as the components in geothermal systems could be easily characterized by their resistivity contrasts. The magnetotelluric method is a geophysical method commonly used to perform this task. This paper performs a three-dimensional inversion based on the complete component of magnetotelluric transfer functions, including impedance tensor and tipper vector. Prior dimensionality analysis using phase tensor revealed that the MT data contains a high dimensionality distortion and shows significant horizontal geoelectrical variations. The analysis suggests using the MT full components in the inversion process to effectively recover all the geoelectrical features in such a geologically complex area. The three-dimensional inversion was then carried out after taking control of the model mesh dimension and the regularization parameter. The 3-D resistivity model showed an overburden layer with varying resistivity in the shallow depth. In the subsequent layer, a conductive anomaly representing impermeable cap rock is distributed from the center to the northern and western parts of the study area, bordered by faults and manifestations. The reservoir zone is located under the center of Mount Seminung at an approximate depth of 1500 m. The heat source is expected to be the residual eruption magma of the volcano, which sits far under the reservoir zone and is unreachable by the MT signal. All the findings agree with the existing geological and geochemical survey data and can explain the hydrothermal activities in the Danau Ranau geothermal prospect area.

Experimental Study on Unsteady Radon Exhalation from the Overburden Layer of the Uranium Mill Tailings Pond under Rainfall

In order to find out radon reduction performance of the overburden layer on uranium mill tailings (UMTs) pond beach surface after rainfall, the rainfall simulation experiment of the overburden layer was carried out with the self-developed equipment. Based on the radon migration model of the overburden layer on the UMTs pond beach surface, the change rule of radon exhalation in four types of compactness of the overburden layer within 120 hours after rainfall was studied, and the corresponding moisture content was also analyzed. The results show that the radon concentration in the overburden layer of UMTs increases nonlinearly; the dynamic change in moisture content of the overburden layer on the beach surface leads to the unsteady radon exhalation. The variation of radon exhalation shows three stages: increase, linear decrease, and stability tendency. After rainfall, radon exhalation rate increases due to water vapor and there is free radon seepage in pores. With the decrease of free radon production rate, radon exhalation rate gradually decreases until it reaches stability again. When the thickness of the overburden layer reduces, the porosity decreases with the increase in compactness of the overburden layer. While the decrease in radon reduction is more obvious, the less time it takes for radon exhalation to vary from unstable to stable overburden after rainfall.

A novel thermal stimulation approach for natural gas hydrate exploitation —— the application of the self-entry energy compensation device in the Shenhu sea

Thermal stimulation is a common measure used to improve the decomposition efficiency of natural gas hydrate. However, the conventional thermal stimulation methods require considerable investments in wellbore construction. According to the penetration mechanism of the torpedo anchor, the self-entry energy compensation device (ECD) is innovatively proposed to replace the existing wellbore platform. The principle and critical technologies of the ECD are described and analyzed in detail. Then, a penetration model and an exploitation model are developed using the reservoir data from the W17 station in the Shenhu sea area, and the main conclusions are: It takes about 4 s for the ECD to penetrate from the overburden layer to the reservoir, and its penetration depth is about 50.1–370.4 m, which covers the buried depth of most marine reservoirs. Nevertheless, the combined depressurization + thermal stimulation method is unsuitable for the Shenhu reservoir due to the low permeability, low thermal conductivity, and high initial temperature. Overall, the ECD can provide a new idea for developing the NGH thermal stimulation method to solve the Joule-Thomson effect and seawater freezing problems during the depressurization production.

Genesis Analysis and Stability Evaluation of Karst Area in the Mudengdong Village Based on the Geological Investigation and Numerical Simulation Methods

The large-scale mining of underground mineral resources will lead to the formation of mined-out areas, which will lead to a series of geological and environmental problems. By selecting the Mudengdong village as a case study, this paper uses geodetic satellite remote sensing technologies to perform qualitative analyses and summarize the geological engineering conditions of the factory. Afterwards, the predominant factors that affect the stability of foundation are determined based on the geological survey of karst in goaf structures. Finally, the finite element software ANSYS is used to comprehensively study the karst problem. The results indicate that (1) the karst development pattern in the study area is controlled by the Beiyin mountain fault, in which case the karst in the basin, in the foot slope, or in the pass section is more widespread than in the slope section. Moreover, the karst generally has a vertical form and is in the early karst stage of development; (2) surface rainwater infiltration, earthquakes, and load pressure are the three major factors that affect karst collapse in the study area; (3) by simulating the development of karst caves and the bearing capacity of the karst roof in the goaf structure under different conditions, it is recommended that only civil buildings with not more than three floors can be built in the village. Overburdened soil thicknesses between 6 and 10 m and civil buildings with heights less than 6 m are not suitable parameters for construction activities. If there are hidden soil holes under the overburden layer, dynamic consolidation needs to be applied in order to destroy the structure of the soil layer and to ensure the safety of personnel.