Deep Alluvium Research Articles

Fuzzy random sensitivity analysis for the overall structure reliability of reinforced concrete freezing wellbores in deep alluvium based on hidden Markov model

To address the shortcomings of traditional reliability theory in characterizing the stability of deep underground structures, the advanced first order second moment of reliability was improved to obtain fuzzy random reliability, which is more consistent with the working conditions. The traditional sensitivity analysis model was optimized using fuzzy random optimization, and an analytical calculation model of the mean and standard deviation of the fuzzy random reliability sensitivity was established. A big data hidden Markov model and expectation-maximization algorithm were used to improve the digital characteristics of fuzzy random variables. The fuzzy random sensitivity optimization model was used to confirm the effect of concrete compressive strength, thick-diameter ratio, reinforcement ratio, uncertainty coefficient of calculation model, and soil depth on the overall structural reliability of a reinforced concrete double-layer wellbore in deep alluvial soil. Through numerical calculations, these characteristics were observed to be the main influencing factors. Furthermore, while the soil depth was negatively correlated, the other influencing factors were all positively correlated with the overall reliability. This study provides an effective reference for the safe construction of deep underground structures in the future.

ENERGY EFFICIENCY IN AGROFORESTRY PARCELS IN ALLUVIAL MINING AREAS UNDER ECOLOGICAL SUCCESSION IN THE MUNICIPALITY OF EL BAGRE - ANTIOQUIA (COLOMBIA)

<p><strong>Background.</strong> The agroforestry parcels are processes of ecological succession that, through technical activities applied to the soil, the areas intervened by the intensive mining operation of deep alluvium are recovered and adapted to biodiverse areas that transform the intervened landscape into productive and environmentally healthy areas with a very marked concept towards family farming. <strong>Objective.</strong> To analyze the energy efficiency in the production of agroforestry plots located in alluvial mining areas in processes of ecological succession, in the municipality of El Bagre - Antioquia. <strong>Methodology.</strong> A field evaluation was carried out in the "agroforestry parcels" located in the municipality of El Bagre, department of Antioquia - Colombia. A sustainability analysis was carried out through the evaluation of indicators and complementary methods such as the rapid evaluation of biodiversity (Institute for Plant Health Research - INISAV, Havana, Cuba), measurement of energy flows and uses, and the application of the Shannon index, as indicators of diversity. <strong>Results.</strong> The findings of this research show the level of energy efficiency of each studied agroforestry parcel and the agroecological characteristics, in terms of sustainability and resilience of the restored areas in the agricultural context of the region. <strong>Implications.</strong> Defining the recovery process of other agroforestry parcels as a successful experience based on the evaluation of agroecology principles, that is, relations of production, society and culture, among other dimensions, can become a tool applicable to the evaluation of recovery processes of ecosystems intervened and degraded by extractive mining practices and support agricultural planning processes. <strong>Conclusions.</strong> These conservation and recovery processes of soils affected by mining may show positive transformations that respond to ecological principles, and this can be demonstrated through the evaluation of sustainability indicators.</p>

Study on seismic safety of Poshitougou flood intercepting dam

Poshitougou dam is located in Xichang City, Sichuan Province. The purpose of the dam is to divert the river section passing through the open-pit mining site to ensure the safe operation of the mining site. The dam is a concrete gravity dam with a length of 148.61m and a height of 34.0m, built on deep alluvium foundation with a depth of 160m. The nearest distance between the dam and the Anninghe fault is 10km, and the fault may have a magnitude 7.5 earthquake in the future, so the seismic safety of the dam is very important. In this paper, the finite element dynamic method is used to analyse the seismic response and dam safety under the design earthquake. According to the calculation results, there are serious potential safety hazards in the dam under strong earthquake, including: collision between adjacent dam sections may occur during the earthquake, causing local damage to the concrete near the joint; joint deformation may tear the water stop, leading to dam leakage; breakage of dam foundation curtain grouting may occur during the earthquake. This paper also discusses the possibility of constructing hardfill dam on deep alluvium foundation in strong earthquake area. The calculation results show that the seismic displacement of the hardfill dam is obviously reduced, the seismic amplification effect of the dam is significantly reduced, the dynamic stress of the dam is smaller and its seismic performance is good.

화강암 분지를 흐르는 미호천의 지형학적 특색

The drainage area of the Miho stream is composed of granitic basins, gneissic and sedimentary mountains. 80 percent of the Miho stream flows through the Jincheon basin and the Cheongju inner-plain within the Daebo granite belt. Because the deep weathering of granitic hills provides a large amount of sands to the streams, there are wide floodplains with thick alluvium developed in the basin and plain. The thickness of the alluvium is 5~10m and the width of the floodplains is 2~2.5km. In the basin outlet area where a stream passes through the mountain canyon, wide floodplains and deep alluvium are developed in other riverside. The Miho stream is a sand-gravel channel flowing through the Cheongju inner-plain with wide floodplains and deep alluvium formed by deep weathering of granite.

Experimental Study on Durability of Hybrid Fiber-Reinforced Concrete in Deep Alluvium Frozen Shaft Lining

This article proposes hybrid fiber-reinforced concrete (HFRC) mixed with polyvinyl alcohol fiber (PVA) and polypropylene steel fiber (FST) as a wall construction material to improve the bearing capacity and durability of frozen shaft lining structures in deep alluvium. According to the stress characteristics and engineering environment of the frozen shaft lining, the strength, impermeability, freeze–thaw damage, and corrosion resistance are taken as the evaluation and control indexes. The C60 concrete commonly used in freezing shaft lining is selected as the reference group. Compared to the reference group, the test results show that the compressive strength of HFRC is similar to that of the reference concrete, but its splitting tensile strength and flexural strength are higher; according to the strength test, the optimum mixed content of 1.092 kg/m3 PVA and 5 kg/m3 FST are obtained. According to the impermeability test results, the mixing of PVA and FST can improve the impermeability resistance of concrete. For the freeze–thaw cycle test results, the mixing of PVA and FST can improve the frost resistance of concrete; based on the 120 days sulfate corrosion test, the mixing of PVA and FST will improve the corrosion resistance of concrete.

Failure criterion for concrete shafts in deep alluvium zones based on plastic ultimate strain and its application

The failure of vertical concrete shafts in the deep alluvium zones is always a troublesome technical problem in coal mines. There is lack of practical failure criteria for such shafts. Therefore, the method of establishing failure criteria of shafts based on the method of ultimate strain was proposed. By regarding concrete as a frictional geomaterial, the formula for the plastic ultimate strain of concrete was constructed according to the theory of generalised plastic mechanics. Furthermore, the ultimate strain when concrete failure was determined using numerical limit analysis method. The numerical limit strain analysis method can be used as a quantitative failure criterion for a concrete shaft. It can directly determine the limit state and failure position. By exploring the shaft deformation during the reduced groundwater level of quaternary aquifers by applying numerical limit analysis method, the failure procedure of concrete shaft was reproduced. It was revealed that the damage to the soil around the shaft preceded that to the shaft; the reduction in groundwater level of aquifers can damage the shaft, while the stress-relief groove delays the failure of the shaft and shifts the failure zone to a greater depth. On condition that water level decreased by 25 m, the sand layer at a burial depth of 158–174 m was damaged; in the case that water level was reduced by 27 m, the shaft at a burial depth of 181–182 m was damaged. After setting a stress-relief groove on the shaft, failure occurred when the groundwater level was decreased by 38 m, implying that the stress-relief groove can release the vertical stress on the shaft.

Seismic Behaviour of RC Building with Raft Foundation in the Ganges Basin, India

Many highly populated and important cities of India are situated in the Ganges basin. Deep alluvium deposit of this basin enhances the earthquake vulnerability of these cities due to amplification of seismic energies in the case of an earthquake. Raft foundations are generally provided for critical facility buildings due to their perceived effectiveness against differential settlement during earthquakes. However, the literature available on seismic behaviour of buildings with raft foundation considering soil deformability is relatively limited. In this context, a full three-dimensional finite element model of a four-storeyed building with raft foundation considering the typical layered soil profile of the Ganges basin has been developed in this study. The effects of different seismic parameters on the structural responses and moments induced in the raft have been studied with ground motions from 10 different earthquakes. Since the alluvium deposit of the Ganges basin is prone to get liquefied, effects of liquefaction of soil on the building with raft foundation have been considered simplistically. The results show that the raft foundation reduces the lateral displacement of the structure considerably. However, an increase in the vertical settlement of the raft in case of liquefiable soil is a matter of concern.

Research and Application of the Local Differential Freezing Technology in Deep Alluvium

Aiming at the complicated engineering conditions of the auxiliary shaft repair in the Banji coal mine, it was proposed to seal the water around the shaft lining by differential control freezing technology using double rows of holes. The outer row of holes is completely frozen, and the inner row of holes is local differential frozen according to the degree of destruction of the shaft lining. The local differential freezing pipe was successfully developed according to engineering requirements. Numeral simulations were used to predict the development of the freezing temperature field; the results showed that the inward expansion range of the frozen wall formed by the inner row freezing holes was effectively limited and the temperature drop rate of the shaft lining was significantly reduced after the local differential freezing technique was adopted. The on‐site monitoring data showed that the temperature of the limited freezing layer was about 5°C higher than that of the conventional freezing layer. During the drainage work and the construction of the new shaft lining, the thickness and average temperature of the frozen wall remained stable, indicating that the implementation of the local differential freezing technology achieved the expected results. Further analysis showed that when the temperature of the limited freezing part of freezing pipes in the inner row was controlled within the range of −15 to −10°C, not only could the frozen wall reach the design thickness and strength but the frost heaving pressure on the existing shaft lining could be effectively eliminated.

Evaluation of variability characteristics of mechanical parameters of artificially frozen clay in deep alluvium

The uncertain mechanical parameters of artificial frozen soil in deep alluvium are the key factors for computing the stochastic stress fields and stochastic deformation fields of artificial freezing engineering. In this study, a series of mechanical parameters tests for the artificially frozen clay are carried out, and the statistical data of elastic modulus, strength and Poisson ratio of frozen clay under three different low temperature conditions (−20 °C, −15 °C and −10 °C) are obtained. The experimental semi-variogram values of the mechanical parameters for artificially frozen clay under different temperature conditions are calculated and analyzed. The results show that the test data meets the requirements of the coefficient of variation analysis and the elastic modulus, strength and poisson ratio basically meet the normal distribution. The variability of the mechanical parameters for artificially frozen clay is basically in the degree of moderate to weak variability. The optimal theoretical variation function model of basic mechanical parameters of frozen clay is Gaussian model. The correlation of soil parameters calculated by Gauss model at smaller distances is greater than that of Exponential model and Spherical model. The mechanical parameters of artificially frozen clay are strongly dependent in spatial range. This study can improve our understanding of the variation characteristics of uncertain mechanical parameters for artificial frozen soil in deep alluvium and provide a theoretical basis and reference for the stochastic mechanical analysis of artificial freezing engineering.

Deflection Mechanism and Treatment Technology of Permanent Derrick of Freeze Sinking on Deep Alluvium

Aiming at the problems of deflection and operation safety of permanent derrick of freeze sinking shafts, the mechanism analysis of uneven settling of the derrick foundations in frost‐thawed soil was conducted. In addition, research on ground stabilization and derrick deviation rectification technologies was also studied in this paper based on the engineering practice of derrick of auxiliary shaft in the Dingji Coal Mine. Firstly, since the soil texture and artificial freeze temperature field are uneven, the bearing capacity and compression modulus of soil mass decrease after freeze thawing, resulting in uneven settlement of the foundation soil of the derrick footing and causing the deflection of the derrick. The finite element numerical analysis indicates that, in the event of uneven settling, the greatest tensile stress in the derrick structure of Dingji auxiliary shaft increased by 39.83% and the largest pressure stress increased by 33.33%. Secondly, this study used sleeve valve pipe single‐fluid static pressure grouting technology to reinforce the foundation of the derrick footing. The reinforced depth of grouting is 32 m, and every derrick foundation has adopted three circles of grouting holes for grouting reinforcement. Meanwhile, the hydraulic synchronous jacking system was used to rectify the deviation of the derrick, restoring the centre line of derrick ascension to the original design state. Finally, the practice of grouting, foundation consolidation, and derrick deviation rectification projects of the Dingji auxiliary shaft suggest that, after grouting reinforcement, the rate of foundation settlement is gradually decreased and tends to be stable. This has resulted in uniform settlement, and through four basic jacking, the deflection of the derrick has been corrected to its initial design state.

Numerical simulation of the temperature fields in the shielding walls of frozen soil with multi-circle-pipe freezing in shaft sinking

In this study, the temperature fields of frozen soil wall were calculated by using numerical method, and were analyzed after the soil was actively frozen with different freezing time. The results showed that the temperature field evolved from the freezing pipes, and then formed into frozen soil cylinders. After a certain freezing duration, the cylinders of frozen soil began to connect, and frozen soil walls started to form. At initial freezing stage, the thickness of frozen soil wall was mainly determined by the freezing pipes of the inner two circles. Then, connections were found to have occurred between the inner and outer frozen soil walls. Finally, the temperature fields of the unfrozen and frozen soils reached a state of stability. The results also showed that it was feasible to use numerical method to simulate the temperature fields of frozen soil walls during shaft sinking process, and potentially provided important references for the design and construction of deep alluvium shaft.

Distribution characteristics of the additional vertical stress on a shaft wall in thick and deep alluvium: a simulation analysis

In order to investigate the mechanisms of shaft lining deformation of coal mines in thick and deep alluvium, we selected Qianyinzi coal mine in the Huaibei mining area in the east of China as the research subject. The structure and stratigraphic composition of the shaft lining of the Qianyinzi coal mine and its geological and hydrogeological conditions and shaft lining deformation characteristics are comprehensively analyzed. The results preliminarily demonstrate that the water loss of the bottom aquifer is the major cause for the shaft lining deformation. On this basis, we designed and manufactured test system consisting of a similar material to simulate the decrease in the bottom aquifer water level and obtain the relationship between the decrease in the water level and the additional vertical stress of the shaft lining and the shaft lining depth. The numerical simulation results indicate a good fit for the equations. The fitting formula can be used to predict the additional vertical stress of the shaft lining based on data of the surface subsidence and bottom aquifer water level changes. The maximum additional vertical stress of the shaft lining is 39.4 MPa. Taking into consideration the stress caused by the self-weight of the shaft lining and tower, which is approximately between 5.0 and 8.0 MPa, the additional vertical stress range between the bottom aquifer and the bedrock interface is between 44.4 and 47.4 MPa. If the additional vertical stress exceeds the allowable reinforced concrete strength of the shaft lining, it may result in shaft lining fractures. In other words, the similarity simulation results are roughly consistent with the numerical simulation results. The results of this study provide an important reference for the prevention of shaft lining fractures in coal mines with similar geological and hydrogeological conditions.

Physical model testing and numerical simulation for temperature distribution of mass concrete freezing shaft lining in deep alluvium

In this study, we conducted an experimental model test and numerical thermal analysis to determine the temperature distribution and thermal gradients of mass concrete freezing shaft lining under the influence of low-temperature frozen soil wall. A non-scaled-down model was built with embedded thermocouple sensors to monitor the temperature distribution of the shaft lining and the frozen soil wall. Transient heat transfer analysis was conducted using ANSYS finite element software to validate the monitoring results of the model test. The temperature distribution at different points along the radial direction in the shaft lining and frozen soil wall are evaluated and compared by using finite element method and experimental work. The results are in good agreement and thus validated.

Vertical Shaft Support Improvement Studies by Strata Grouting at Aquifer Zone

The shaft lining failure which occurs in deep alluvium is a sudden coal mine hazard. The strata grouting is one of the treatment methods for the shaft lining failure. To investigate the impact of grout injection pressure on the shaft lining, the field measurement and the numerical analysis of the shaft lining stress variation during the grouting were conducted. To improve the strata grouting, the underground continuous impervious curtain (UCIC) is proposed as a new method by using the chain conveyor cutter technique without the impact on the shaft lining. The effects of the new method were also analyzed by means of the numerical methods. The results show that the strata grouting in the deep alluvium needs a high injection pressure, and in the horizontal direction, the shaft lining sustains the repeat tensile and compressive force during the grouting process. The negative influence of strata grouting on the stability of the shaft lining is obvious and serious. The UCIC built around the shaft lining can restrain the stress concentration induced by the aquifer drawdown. The triangular UCIC has a similar effect as that of the vertical one, and the small angle is better for preventing the shaft lining failure.

On the challenges of using field spectroscopy to measure the impact of soil type on leaf traits

Abstract. Understanding the causes of variation in functional plant traits is a central issue in ecology, particularly in the context of global change. Spectroscopy is increasingly used for rapid and non-destructive estimation of foliar traits, but few studies have evaluated its accuracy when assessing phenotypic variation in multiple traits. Working with 24 chemical and physical leaf traits of six European tree species growing on strongly contrasting soil types (i.e. deep alluvium versus nearby shallow chalk), we asked (i) whether variability in leaf traits is greater between tree species or soil type, and (ii) whether field spectroscopy is effective at predicting intraspecific variation in leaf traits as well as interspecific differences. Analysis of variance showed that interspecific differences in traits were generally much stronger than intraspecific differences related to soil type, accounting for 25 % versus 5 % of total trait variation, respectively. Structural traits, phenolic defences and pigments were barely affected by soil type. In contrast, foliar concentrations of rock-derived nutrients did vary: P and K concentrations were lower on chalk than alluvial soils, while Ca, Mg, B, Mn and Zn concentrations were all higher, consistent with the findings of previous ecological studies. Foliar traits were predicted from 400 to 2500 nm reflectance spectra collected by field spectroscopy using partial least square regression, a method that is commonly employed in chemometrics. Pigments were best modelled using reflectance data from the visible region (400–700 nm), while all other traits were best modelled using reflectance data from the shortwave infrared region (1100–2500 nm). Spectroscopy delivered accurate predictions of species-level variation in traits. However, it was ineffective at detecting intraspecific variation in rock-derived nutrients (with the notable exception of P). The explanation for this failure is that rock-derived elements do not have absorption features in the 400–2500 nm region, and their estimation is indirect, relying on elemental concentrations covarying with structural traits that do have absorption features in that spectral region (constellation effects). Since the structural traits did not vary with soil type, it was impossible for our regression models to predict intraspecific variation in rock-derived nutrients via constellation effects. This study demonstrates the value of spectroscopy for rapid, non-destructive estimation of foliar traits across species, but highlights problems with predicting intraspecific variation indirectly. We discuss the implications of these findings for mapping functional traits by airborne imaging spectroscopy.

Quaternary history of the Kiseiba Oasis region, southern Egypt

Kiseiba Oasis and depression are located in southern Egypt between the Selima Sand Sheet to the west and the Nile to the east, an important area that hosted Late Cenozoic drainage, Middle Pleistocene lakes, and numerous Paleolithic and Neolithic cultural sites. A synthesis of orbital data, field surveying and near-surface stratigraphy provides new insights into the Quaternary history of this region. Shuttle Imaging Radar data show a complex of fluvial channels that are due to stringers of surficial fluvial lag, subsurface fluvial deposits, and areas of deep alluvium. Three topographic surfaces are described: 1) the Atmur El-Kibeish, above 230 m elevation, which displays a linear pattern of light radar returns, possibly formed from northeast drainage; 2) the Acheulean Surface, at 200 m elevation, that has dark radar patterns resulting from thick alluvium bounded by pebble sand and calcrete strata, and 3) the Kiseiba Surface, below 190 m, that has a complex series of surface and subsurface fluvial and aeolian sediments. Initial drainage from the Early through Middle Pleistocene was to the northeast, which may have lasted through the Last Interglacial. Later reworking of sediments during the Last Glacial Maximum and the Holocene resulted in topographic inversion, with any subsequent local drainage on the Kiseiba Surface to the southwest, towards the Kiseiba Scarp.

Improving seismic hazard approaches for critical infrastructures: a pilot study in the Po Plain

Paper describes the extensive work done in the SIGMA project, aimed at improving knowledge on data, methods and tools to better quantify uncertainties in seismic hazard assessment (SHA). The authors cooperated in the study of potential faults and geological structures, earthquake catalogues, selection of ground motion prediction equations, and methods for site effect evaluation suitable for SHA. All the contributions merged into a probabilistic seismic hazard study conducted for three representative sites of the Po Plain in Northern Italy. Po Plain is a low-to-moderate seismicity region, characterized by some critical features, such as blind faulting and deep alluvium sediments, and by scarcity of strong motion data; these sources of uncertainties in seismic hazard estimation are common to other low seismicity areas around the world. Within SIGMA, special care was devoted to: (a) the use of the single station sigma approach inside the probabilistic SHA, (b) the comparative use of generalized attenuation functions to evaluate the hazard contribution of composite fault systems, and (c) the study of the epistemic uncertainties at play when different modelling approaches to site effects are used.

Study on the freezing characteristics of silty clay under high loading conditions

The freezing behaviour of soil in deep alluvium is one of the important issues in artificial freezing engineering. In this paper, an apparatus was developed for studying the freezing characteristics of soil under high loading conditions and the related test procedures were also suggested. Based on this apparatus, a series of one-dimensional freezing tests were also carried out on silty clay under various loading conditions and pseudo temperature gradients. The results show that all soil samples exhibit compression under high loading conditions, and it consists of four stages in which the strain rate is I) very low, II) rapidly increasing, III) decaying and IV) relatively constant. During freezing tests, the freezing front moves downward rapidly during the initial period, and it tends to be stable after 10h. As the increase of axial load or pseudo temperature gradient, the freezing front moves downward more quickly and lies closer to the warm end at the thermostatic stage. Even under high loading conditions, there is an obvious water redistribution phenomenon, which shows that the water migrated to the frozen part and gathered at the freezing front in the soil sample under the existence of a pseudo temperature gradient.

Preparation Experiment and Engineering Application of High Performance Concrete of Freezing Shaft in Deep Alluvium

According to the special construction environment and curing conditions of the freezing shaft inner and outer shaft lining in deep alluvium, first,configuration principle of high strength high performance concrete of freezing shaft in deep alluvium is proposed; Then raw materials are selected according to the preparation approach, and preparation experimental study of high strength high performance concrete is conducted with C60, C65, C70and C75 , and the optimum mixture ratio is obtained, and applied to the engineering practice, achieving remarkable effect.

Dynamic Interaction between Reservoir and a High Concrete Face Rockfill Dam on Deep Alluvium Deposit

Potential-based fluid model and Westergaard added mass model were used to reflect the dynamic interaction of reservoir-CFRD(concrete face rockfill dam)-foundation coupling system. The deep alluvium deposit was treated as porous medium using Biot's dynamic consolidation theory. In the coupled analysis, the paper focused on hydrodynamic pressures in the reservoir zone, dynamic response and pore water pressure in the structure zone. The result shows that the dynamic response of added mass model is greater than that of potential-based fluid model. The porous medium of alluvium deposit is of great significance in performing soil liquefaction analysis and reservoir-dam-foundation system.