Numerical analysis of stability for mined-out area in multi-field coupling

There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.

Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area

Dynamic analysis steps and general flow of fast lagrangian analysis of continua in 3 dimensions(FLAC3D) were discussed. Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area was carried out with FLAC3D. The whole analytical process was divided into two steps, including the static analysis and the dynamic analysis which were used to simulate the influence of excavation process and blasting vibration respectively. The results show that the shape of right upper boundary is extremely irregular after excavation, and stress concentration occurs at many places and higher tensile stress appears. The maximum tensile stress is higher than the tensile strength of rock mass, and surrounding rock of right roof will be damaged with tension fracture. The maximum displacement of surrounding rock is 4.75 mm after excavation. However, the maximum displacement increases to 5.47 mm after the blasting dynamic load is applied. And the covering area of plastic zones expands obviously, especially at the foot of right upper slope. The analytical results are in basic accordance with the observed results on the whole. Damage and disturbance on surrounding rock to some degree are caused by excavation, while blasting dynamic load increases the possibility of occurrence of dynamic instability and destruction further. So the effective supporting and vibration reducing measures should be taken during mining.

Instability identification on large scale underground mined-out area in the metal mine based on the improved FRBFNN

To identify the instability on large scale underground mined-out area in the metal mine effectively,the parameters of radial basis function were determined through clustering method and the improved fuzzy radial basis function neural network(FRBFNN)model of instability identification model about large scale underground mined-out area in the metal mine was built.The improved FRBFNN model was trained and tested.The results show that the improved FRBFNN model has high training accuracy and generalization ability.Parameters such as pillar area ratio,filling level and the value of rock quality designation have strong influence on instability of large scale underground mined-out area.Correctness of analysis about the improved FRBFNN model was proved by the practical application results about instability discrimination of surrounding rock in large-scale underground mined-out area of a metal mine in south China.

Quantitative analysis of biotechnical reinforcement for a steep slope consisting of composite coal-gangue-soil medium adjacent to a mined-out area

The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vegetation and porous characteristics of the soil and rock mass, the steep slope will be destabilized and induce mud-rock flow or derive hazard easily. Firstly, based on the classical slope reinforcement theory, some regularity between the shear and displacement in the destabilized zone of the slope with or without root strength contribution is presented. Then, based on the experimental and statistical analysis of root strength, hydrological characteristics and stability status, etc., some possible biotechnical techniques for reinforcement of the steep slope have been suggested. These methods are important for quantitative analysis of destabilization of the slope and design of the biotechnical reinforcement.

Time function of surface subsidence based on Harris model in mined-out area

The surface subsidence is a common environmental hazard in mined-out area. Based on careful analysis of the regularity of surface subsidence in mined-out area, we proposed a new time function based on Harris curve model in consideration of the shortage of current surface subsidence time functions. By analyzing the characteristics of the new time function, we found that it could meet the dynamic process, the velocity change process and the acceleration change process during surface subsidence. Then its rationality had been verified through project cases. The results show that the proposed time function model can give a good reflection of the regularity of surface subsidence in mined-out area and can accurately predict surface subsidence. And the prediction data of the model are a little greater than measured data on condition of proper measured data quantity, which is safety in the engineering. This model provides a new method for the analysis of surface subsidence in mined-out area and reference for future prediction, and it is valuable to engineering application.

Relationship between body surface area and ALT normalization after long-term lamivudine treatment

AIM： To further evaluate the relationship between BSA and the effects of lamivudine in a greater number of cases and over a longer period of observation than in our previous evaluation. METHODS： We evaluated 249 patients with chronic hepatitis B. The effects of treatment for one year （n = 249）, two years （n = 147）, and three years （n = 72） were evaluated from the levels of serum ALT and HBVoDNA, as biological and virological effects （undetectable levels by PCR）, respectively. Moreover, several variables that could influence the response to treatment, including ALT, albumin, bilirubin, platelet counts, BSA, HBVoDNA, and HBeAg were analyzed. RESULTS： For 1-year treatment, multivariate analysis revealed that BSA （P = 0.0002） was the only factor for the biological effect, and that ALT （P = 0.0017）, HBV- DNA （P = 0.0004）, and HBeAg （P = 0.0021） were independent factors for the virological effect. For 2-year treatment, multivariate analysis again showed that BSA （P = 0.0147） was the only factor for the biological effect, and that ALT （P = 0.0192） and HBeAg （P = 0.0428） were independent factors for the virological effect. For 3-year treatment, multivariate analysis, however, could not reveal BSA （P = 0.0730） as a factor for the normalization of ALT levels. CONCLUSION： BSA is a significant predictor for the normalizing the effect of lamivudine therapy on ALT for an initial 2-year period, suggesting that lamivudine dosage should be based on the individual BSA.

Experimental Study on Afforestation in the Engineering Treatment Areas in the Hydro-fluctuation Zone of the Three Gorges Reservoir:A Case Study on the Engineering Treatment Area in the Wuxi Section of the Daning River

Through the Betula nigra afforestation test in the engineering treatment area of the Wuxi Section of the Daning River in Chongqing,the feasibility of arbor vegetation restoration in the comprehensive management of the engineering treatment areas of the Three Gorges Reservoir was explored.The results showed that:(1)before the flooding in the project area,the survival rate of B.nigra seedlings was high,over 95%,and(2)in 2021,after a water storage period,affected by factors such as seedling specifications,flood and flooding time,the survival rate of the seedlings planted in 2020 was low,and the one-year-old seedlings were greatly competed by weeds and grew less.Two-year-old B.nigra seedlings were replanted in 2021,and the survival rate of the B.nigra seedlings was 100%in 2022.Two-year-old B.nigra seedlings have strong adaptability and have little impact on the stability of the engineering treatment area,and can be used as afforestation tree species in engineering treatment areas of hydro-fluctuation zones.

Influence of laser treatment on the fatigue of notched bar

Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.

Evaluation of phosphorus removal from wastewater by soils in rural areas in China

Low-cost, easy-maintenance and high-efficiency decentralized wastewater treatment technologies are urgently needed in rural areas of China. Processes with high potential for phosphorus removal are of great interest. However, commonly used treatment methods often do not meet the strict criteria for removing phosphorus from rural wastewater. In order to search an economic and simple technology for phosphorus removal from the common bit-technologies effluent, seven soil types collected from different rural areas in China were investigated for their ability to remove phosphorus. X-ray diffraction （XRD） was used to analyse the mineral structure, and inductively coupled plasma optical emission spectrometer （ICP-OES） was used to analyse the geochemical composition of the soil samples. Three primary minerals - quartz, albite and montmorillonite - were clearly detected. The samples were divided into two soil types, acidic soils and alkaline soils, based on their pH values. The geochemical composition study indicated that a higher percentage of Ca and Mg occurred in alkaline soils （pH 〉 8） than in acidic soils （pH 〈 6.5）. Adsorption isotherms from batch experiments fitted the Langmuir and Freundlich models well, the maximum P adsorption capacities ranged from 0.256 to 1.598 mg P/g, indicating a high phosphorus removal potential for all of these soils. The P fractions extracted revealed that the sum of NaOH-extracted inorganic P （NaOH-Pi） was the major P component in the acidic soils, and CaCO3-bound phosphorus （Ca-P） in the alkaline soils. Dynamic adsorption simulation showed that these soils have the ability to remove phosphorus from wastewater.

Effect of ultrasonic peening treatment on the fatigue behaviors of a magnesium alloy up to very high cycle regime

Ultrasonic fatigue tests are performed on a magnesium alloy with and without ultrasonic peening treatment(UPT).Surface enhancement layer leads to the complete change of crack initiation sites.However,crack initiation mechanism keeps the same and results in a single-faceted morphology at crack initiation site.Microcracks initiate as Mode Ⅱ crack within the original grain,but deflect to Mode I crack outside of the original cracked grain.A threshold SIF value is proposed to evaluate the retarding effect of grain boundary on microcrack propagation.Outside of the original cracked grain,Mode I crack propagation below the threshold ΔK_(σ-th) is responsible for the formation of fine granular area(FGA,a nano-grain layer).Based on the Numerous Cyclic Pressing(NCP) model,it is proposed that crack type should be another necessary condition for the formation of FGA.

Effect of Heat Treatment on Silica Aerogels Prepared via Ambient Drying

Silica aerogels were prepared at ambient drying by using ethanol/trimethylchlorosilane （TMCS）/heptane solution as pore water exchange and surface modification of the wet gel before drying. The obtained silica aerogels exhibit a sponge-like structure with uniform pore size distribution. The effects of heat-treatment on the hydrophobicity, specific surface area and other properties were investigated. The results indicated that the hydrophobicity of silica aerogels could be maintained up to 350℃. With increasing heating temperature, hydrophobicity decreased, and became completely hydrophilic after heat-treatment at 500℃. Brunaueremmitt-teller （BET） surface area results indicated that the specific surface area of silica aerogels increased with increasing heating temperature in the range of 150-500℃. The effects of heat-treatment on the morphology and chemical bonding state of silica aerogels were investigated by scanning electron microscopy （SEM）, differential temperature analysis （DTA） and Fourier-transform infrared spectroscopy （FT-IR）.

Significance of Substrate Selection in the Efficiency of Wastewater Treatment in Constructed Wetlands (CWs)

Constructed wetlands (CWs) can achieve a high-quality wastewater treatment and a quality that meets the prescribed standard, defined by legislation on wastewater discharge. A limitation in the application of constructed wetlands (CWs) is the large area requirement, which limits their application. The subject matter of this research is to check the possibility of improving the efficiency of wastewater treatment and reducing the required area for constructed wetlands (CWs) by using an adequate substrate under the conditions found in Montenegro. In the described experiment, the constructed wetlands (CW) have a vertical flow system and play the role of a secondary wastewater treatment, receiving water from the existing WWTP in Podgorica after the primary treatment. These vertical flow systems reflect experience with the use of similar systems in Slovenija, Austria and Italy. Measurements to date show that the substrate plays an important role and that wastewater treatment efficacy varies significantly with respect to the type of substrate when used under the conditions available in Montenegro.

Assessing the effects of alternative fuel treatments to reduce wildfire exposure

Effective landscape-scale fuel management strategies are essential for reducing wildfire risk in Mediterranean fire-prone areas.In this study,the minimum travel time(MTT)fire-spread algorithm as implemented in FlamMap was applied to assess the potential of alternative fuel treatments for lowering wildfire losses in a 5,740-ha study area in eastern Sardinia,Italy.Twenty-seven wildfires at 10-m resolution were simulated considering three wind speeds(15,18,and 21 km h-1)to compare fuel treatments:no treatment(NT),irrigated agroforestry areas with shrub clearing(T1),prescribed fire in eucalyptus stands(T2),and irrigated grasslands(T3).The simulations replicated a recent large wildfire that occurred in the study area(Orrìwildfire,2019)and considered the weather and fuel moisture conditions associated with this event.The average wildfire exposure outputs(burned area,probability of burning,conditional flame length,potential crown fire occurrence,and surfaces withflame lengths above 2.5 m)decreased after fuel treatments,compared to no treatment.T1 was the most effective strategy in mitigating wildfire hazards and provided the most significant performance for several wildfire exposure indicators.Treating only 0.5%of the study area(~30 ha)resulted in a decrease in all wildfire exposure metrics to~10%within the study area.In addition,the total surface characterized by high flame length(average>2.5 m)was the lowest in the T1 treatment.This study can help land and fire managers optimize fuel treatment opportunities and wildfire risk mitigation strategies in Mediterranean areas.

Twelve-month evaluation of the atraumatic restorative treatment approach for class Ⅲ restorations:An interventional study

BACKGROUND Atraumatic restorative treatment(ART)may be appropriate for populations without accessibility and affordability.More data are required regarding the success rate of ART in anterior teeth.AIM To evaluate the clinical performance of restoring class III cavities in anterior teeth of permanent dentition using the ART approach.METHODS A longitudinal interventional field study was carried out at two rural primary health centers,Tumkur district,India.A total of 54 teeth in 39 patients were evaluated for the survival rate of class III restorations in permanent anterior teeth using the ART approach in children and adult populations.Evaluation of ART restoration was carried out using Frencken J criteria,the mean procedure time,patient acceptance and reported pain severity during the ART approach were evaluated using a visual analog scale.Calculation of the cost of ART was also performed.RESULTS The mean time taken to perform the ART procedure was 14.79±5.8 min with the majority of patients reporting only mild pain.At 6 mo follow-up,72.2%remained in a good state,but this reduced to 27%at 12 mo.The cumulative survival rate of the restorations was 94.4%at 6 mo and 80.9%at 12 mo follow-up.Estimation of the direct cost for a single class III restoration was 186.50 INR(2.64 USD).CONCLUSION ART may be a good comprehensive option for basic oral health care for underserved or inaccessible populations,and preventive care for patients.

Adult Onset Still’s Disease in Tropical Area: Illustration of Diagnostic and Therapeutic Difficulties from 3 Senegaleses Observations

Introduction: The Adult Onset Still’s Disease (ASD) is a systemic auto-inflammatory affection of unknown cause seldom described in sub-Saharan Africa. We report 3 observations of ASD illustrating the diagnostic and therapeutic difficulties of this affection in our areas. Observation 1: Our first patient is a 56 years old schoolteacher presenting an ASD in its chronic articular form. She had been followed for an inflammatory arthralgia for 10 years and of the pharyngal pains without exact diagnosis. She presented ASD’s criteria of Yamaguchi and of Fautrel. The prednisone was begun at the dose of 0.8 mg/kg/day with fast appearance of a progressive muscular weakness. Use of methotrexate at a rate of 15 mg per week, associated with low dose of prednisone was effective in long-term without any flare of the disease so far. Observation 2: Our second patient is a 30 years old dressmaker presenting an ASD in its complicated systemic form of lymphohistiocytic activation syndrome. She validated the criteria of Yamaguchi and Fautrel for ASD. She also presented resistance to corticosteroid therapy. The evolution was marked by a hospital-acquired septicemia and a multi-organ failure leading to death. The diagnosis was retrospectively confirmed after that, with the low level of the glycosylated ferritin serum value. Observation 3: The third patient is a 22 years old Guinean student who presented prolonged fever and inflammatory polyarthralgia without articular deformation. He had been misdiagnosed for ASD with diagnostic wandering of several months. He was treated successfully with prednisone after set up of ASD diagnosis according common criteria. Corticosteroid therapy was stopped after 8 months without any relapse noted so far. Conclusion: Caring for ASD is difficult in our context mainly because of high cost of several explorations needed to set up its exact diagnosis while making differential one. Evolution under corticosteroid therapy is usually favorable but diagnostic delay may lead to severe complications and death.

Study on the Present Situation and Strategies of Rural Waste Classification Treatment in Northeast China

The classification treatment of rural domestic waste is not only an important measure to realize the standardized development in rural areas,but also the action support to the concept of"ecological and suitable residence"put forward by the 19th CPC National Congress.This paper summarizes the traditional treatment methods of rural domestic waste in Northeast China,the present situation of rural waste classification treatment in Northeast China and the advantages of waste classification in rural areas of Northeast China.The specific measures to improve the current situation of rural waste classification treatment in Northeast China are put forward in terms of capital policy,classification methods and management means,in order to provide theoretical reference for the treatment of rural domestic waste in Northeast China.

Study on the Current Situation and Countermeasures of Rural Domestic Sewage Treatment in Beijing City

In recent years,the construction of rural sewage treatment in Beijing City has developed rapidly,but there are still many problems in some rural domestic sewage treatment. In this paper,the current situation of rural domestic sewage in Beijing City is combed,and its characteristics are summarized. Meanwhile,the current situation of rural domestic sewage treatment in Zhejiang Province,Hunan Province and Shandong Province is summarized by consulting relevant data. By comparing with current situation of rural domestic sewage treatment in Beijing City,it is found that there are some problems in the treatment of rural domestic sewage in Beijing City,such as unsuitable treatment mode,unreasonable discharge requirements and inadequate treatment technology. Therefore,some countermeasures and suggestions are proposed,such as strengthening the investigation,research and planning,and differential formulation of the sewage treatment discharge standards,and establishing modular treatment technology system. It is hoped that this paper will be helpful to the treatment of rural domestic sewage in Beijing City.

富水沟谷区浅埋煤层导水裂隙演化特征

富水沟谷区域下浅埋煤层赋存条件特殊,采场上覆岩层导水裂隙发育演化特征复杂。为了揭示沟谷区浅埋煤层在回采扰动作用下覆岩裂隙演化规律,以朱家峁煤矿1305-2工作面过沟谷区回采阶段为工程背景,采用理论分析、物理相似模拟、数值模拟与现场效果验证的方法,建立了覆岩裂隙−渗流场概念模型,开展了覆岩结构发育与微震能量演化研究,分析了覆岩变形与塑性破坏分布特征,提出了针对沟谷区下浅埋煤层导水裂隙防治措施,并应用于现场工程实践。结果表明:开采扰动下裂隙−渗流场模型呈“梯台”结构,并依次划分为初渗区域、稳渗区域、紊渗区域3个区域;将所研究矿井的工况数据代入模型结构,计算出各个渗透区域范围,并根据计算结果对矿井的稳渗区域采取注浆措施。工作面回采至沟谷区段,覆岩裂隙域形态呈现“拱形-梯形-复合梯形”的扩展演化特征,裂隙纵向发育高度达到163 m,并与沟谷区地表贯通。随工作面推进,地表裂隙依次经历“滑移-挤压-撕裂”过程;沟谷区域位移云图呈现出滞后开采“高位梯形”破断形态,在沟底处下沉位移最大,达3.47 m。针对开采导致的裂隙大范围扩展贯通,提出在地面进行采动裂缝注浆处理,在工作面上覆岩层进行注浆封堵,实现过沟谷区开采“井上−井下”联合防治,保证安全开采。该研究结果可为浅埋煤层的过沟谷区开采、采动裂隙防治及富水区“保水采煤”提供新的科学依据。

Natural Gas Prospecting by Using Satellite MT Data in Chishui Area,Guizhou

Oil-gas remote sensing information is obtained from satellite TM data through graph-ic treatment in the light of the hydrocarbon-microseepage theory. The nine target areas (ofthree types) selected on this basis coincide well with the occurrence of natural gases and have been proved by subsequent prospecting. Plants in the target areas are characterized, as a result of hydrocarbon- microseepage, by abnormal spectral features with the absorption peaks of chlorophyll shifting toward blue light, reflectivity in the range of visible light increasing and re-flectivity in the near infrared region decreasing.

岩溶凹陷式露天矿山大流量涌水治理技术

我国岩溶地质分布广泛,岩溶突涌水已成为石灰石矿山安全生产的巨大灾害与挑战。以广西某岩溶凹陷式露天矿山大流量涌水为研究对象,针对该矿山地质条件复杂、集中涌水量大、流速高等特点,利用岩溶发育特征、资料分析与地球物理探查等方法初步圈定矿山径流带区域;进一步通过钻探、跨孔CT和示踪联通试验等精准查找到矿山Y01特大涌水点岩溶管道的具体位置,在此基础上研究并实施了矿山涌水治理技术与工艺。研究表明:(1)针对复杂岩溶凹陷式露天矿山大流量、高流速的涌水特征,提出并实施了“非连续帷幕截流+关键通道探查与封堵+止浆垫控流降速”的岩溶矿山涌水综合治理体系。依据岩溶发育的不均匀性,提出了非连续帷幕封堵裂隙型涌水区域的思想;对大流量岩溶管道型集中涌水设计采用止浆垫控流装置,通过控流能有效降低关键过水通道内水流速度,为注浆材料的有效留存沉积和工程的成功封堵提供了重要条件。(2)关键孔联合注浆工艺是岩溶管道型涌水成功封堵的保证,关键孔是指直接揭露岩溶涌水管道或与涌水管道联通性极强并对注浆堵水起主要作用的钻孔。针对矿山Y01岩溶管道型特大涌水精准查找到2个关键孔,均在矿坑南部:一个是距涌水点直线距离约50 m的近距离钻孔(以下简称“近孔”),另一个是距涌水点直线距离约150 m的远距离钻孔(以下简称“远孔”)。现场采用近孔、远孔2个关键孔联合注浆工艺:近孔以粗骨料和自主研发的可控凝结新型材料进行注浆,远孔仅注水泥浆液;近孔粗骨料和新型材料既能降低管道内的水流速度为远孔浆液起到更好的留存沉积作用,又能作为封堵材料起到增强的功能,远孔因其离涌水点距离长、辐射范围广、浆液扩散充分而能确保封堵长度和效果。近孔、远孔协同配合同步注浆是封堵管道型大流量涌水的有效组合工艺。(3)涌水口止浆垫控流降速装置的合理有效调控,配合关键孔联合注浆工艺的同步实施,进一步确保了注浆浆液的有效快速留存和沉积,是岩溶地区封堵管道型大流量涌水的创新性技术和方法。项目实施后,彻底封堵矿坑内集中涌水量达7.12万m^(3)/d的Y01特大涌水点,实现总减水量8.43万m3/d(含非连续帷幕注浆封堵),保证了矿山的正常安全开采,大幅降低了抽排水费用,同时保护了周边环境和地下水资源,具有显著的经济效益和社会效益。研究成果可为我国矿山涌水灾害治理提供理论价值和经验借鉴。