A study on mixed coal simulation soft layer of gas adsorption

Based on the single coal adsorption gas, hard coal and soft coal of intake airway in Shanxi Heshun Tianchi Coal Mine were chosen to simulate the soft coal seams in coalbed as those in different qualities are mixed with delamination. Experiments on characteristics of adsorption gas of hard coal and soft coal in different quality ratios were done according to the Langmuir single molecule layer absorption theory. Gas constant mensuration instrument WY-98B was used during the experiments. Isothermal adsorption curves, adsorption constants a and b of the mixed coal samples in different quality ratios were established for qualitative and quantitative analysis. The relationship curves of adsorption quantity with changing pressure and variation equation of adsorption constants a, b with changing thickness ratio shows that the thickness of soft layer and hard coal approximately equal, thus resulting in outburst at greatest risk, then a theoretical base for the mechanism of coal and gas outburst has been put forward and a technical support scheme for engineering control of gas outburst is laid out.

Physical model test and numerical simulation on the failure mechanism of the roadway in layered soft rocks

To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.

A three-layer structure model for the effect of a soft middle layer on Love waves propagating in layered piezoelectric systems

A three-layer structure model is proposed for investigating the effect of a soft elastic middle layer on the propagation behavior of Love waves in piezoelectric layered systems, with ＂soft＂ implying that the bulk-shear-wave velocity of the middle layer is smaller than that of the upper sensitive layer. Dispersion equations are obtained for unelectroded and traction-free upper surfaces which, in the limit, can be reduced to those for classical Love waves. Systematic parametric studies are subsequently carried out to quantify the effects of the soft middle layer upon Love wave propagation, including its thickness, mass density, dielectric constant and elastic coefficient. It is demonstrated that whilst the thickness and elastic coefficient of the middle layer affect significantly Love wave propagation, its mass density and dielectric constant have negligible influence. On condition that both the thickness and elastic coefficient of the middle layer are vanishingly small so that it degenerates into an imperfectly bonded interface, the three-layer model is also employed to investigate the influence of imperfect interfaces on Love waves propagating in piezoelectric layer/elastic sub- strate systems. Upon comparing with the predictions ob- tained by employing the traditional shear-lag model, the present three-layer structure model is found to be more ac- curate as it avoids the unrealistic displacement discontinuity across imperfectly bonded interfaces assumed by the shearlag model, especially for long waves when the piezoelectric layer is relatively thin.

Time-dependent squeezing deformation mechanism of tunnels in layered soft-rock stratum under high geo-stress

Large squeezing deformation of layered soft rock tunnel under high geo-stress has a significant time-dependent deformation behavior.In this paper,we studied the deformation mechanism during the construction period of deep-buried softrock tunnel by means of a combination of field observations and a numerical method.First,a new classification criterion for large deformations based on the power exponent variation law between the deformation and the strength-stress ratio is proposed.Then,the initial damage tensor reflecting the bedding plane(joint)distribution and an equivalent damage evolution equation derived from the viscoplastic strain are introduced based on the geometric research method,i.e.,a new rheological damage model(RDL model)of layered soft rock is established consisting of elastic,viscous,viscoelastic,viscoplastic and plastic elements.A field test was conducted on the Maoxian tunnel in Sichuan province,southwestern China,which is in broken phyllite(layered soft rock)under high geo-stress.The tunnel has experienced large deformation due to serious squeezing pressure,thus we adopted double primary support method to overcome the supporting structure failure problems.The rheological parameters of phyllite in the Maoxian tunnel were recognized by using SA-PSO optimization,and the RDL model does a good job in describing the time-dependent deformation behavior of a layered soft-rock tunnel under high geo-stress.Thus,the RDL model was used to investigate the supporting effect and bearing mechanism of the double primary support method.Compared with the single primary support method,the surrounding rock pressure,secondary lining force,surrounding rock deformation,and the depth of the damage to the rock mass was reduced by 40%-60%after the double primary support method was used.

Numerical simulation for rheological characteristics of alternating distribution of soft and hard rock layers

The difficulty of selecting appropriate rheological model and parameters for the alternating distribution of soft and hard rock layers was often encountered due to the unhomogeneity, discontinuity and anisotropy of rock mass. The Burgers and generalized Kelvin models were applied to the soft and hard rock respectively and the rheological parameters were obtained based on the method of optimum separation. By using the simulated code FLAC^(3D), the stability of surrounding rocks of a certain underground plant was analyzed. The effect of surface load and weakening the parameters intensity of argillaceous and bioclastic interlayers between soft and hard rock on rheological behavior of layer composite rock mass was investigated. The results indicate that the rheological characteristics of soft and hard rock layer in composite rock mass can be described well with above two rheological models.

An Innovative Soft Design Science Methodology for Improving Development of a Secure Information System in Tanzania Using Multi-Layered Approach

This paper presents an innovative Soft Design Science Methodology for improving information systems security using multi-layered security approach. The study applied Soft Design Science Methodology to address the problematic situation on how information systems security can be improved. In addition, Soft Design Science Methodology was compounded with mixed research methodology. This holistic approach helped for research methodology triangulation. The study assessed security requirements and developed a framework for improving information systems security. The study carried out maturity level assessment to determine security status quo in the education sector in Tanzania. The study identified security requirements gap (IT security controls, IT security measures) using ISO/IEC 21827: Systems Security Engineering-Capability Maturity Model (SSE-CMM) with a rating scale of 0 - 5. The results of this study show that maturity level across security domain is 0.44 out of 5. The finding shows that the implementation of IT security controls and security measures for ensuring security goals are lacking or conducted in ad-hoc. Thus, for improving the security of information systems, organisations should implement security controls and security measures in each security domain (multi-layer security). This research provides a framework for enhancing information systems security during capturing, processing, storage and transmission of information. This research has several practical contributions. Firstly, it contributes to the body of knowledge of information systems security by providing a set of security requirements for ensuring information systems security. Secondly, it contributes empirical evidence on how information systems security can be improved. Thirdly, it contributes on the applicability of Soft Design Science Methodology on addressing the problematic situation in information systems security. The research findings can be used by decision makers and lawmakers to improve existing cyber security laws, and enact laws for data privacy and sharing of open data.

Enhancing Mar and Abrasion Resistance of Acrylic Hard Coatings with Soft Base Layer

Mar and abrasion resistance were investigated by a progressive load scratch test and steel wool abrasion test, respectively. Two acrylic coating systems including trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) were prepared. A soft base layer was introduced as an intermediate layer between two different types of top layer and poly (methyl methacrylate) (PMMA) substrate to demonstrate the effect of soft base layer on mar and abrasion resistance. Abrasion damage on the coating surface was found to be less severe, when the soft base layer was incorporated into the coating systems. The reduction in scratch coefficient of friction (SCOF) and surface roughness was also observed. The results suggested that mar and abrasion resistance was greatly influenced by the presence of soft base layer, although different top layers were used. Moreover, it was found that abrasion resistance was further improved as the thicker soft base layer was applied.

Response of Surface Soft Soil and Fine-Grained Sand Layers to Seismic Waves

Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy casualties and property losses have a direct relationship with overburden soil layers. Ground motions caused by earthquakes are significantly amplified when passing through the soil layers. Under the influence of these amplified motions, building structures, whose nature frequency is within the frequency band of soil amplification response, will experience more severe damage than those built on bedrock. Therefore, engineering seismologists have paid considerable attention the amplification responses in the Shanghai overburden soil layers. The amplification responses of soil and sand layers in this paper are given by the M L=4.1 earthquake in Nantong, Jiangsu Province on December 25, 2001 at 31.8° N, 120.9° E. It can be seen that the responses of soil and sand layers are very different. That is important.

混合阻塞变刚度软手指设计与实验

为了解决单一阻塞介质变刚度软机械手抓取复杂外形物体效果不佳的问题,受人体手指结构启发,设计了一种仿指腹结构的混合阻塞变刚度软手指。将其设计为双层结构,外层为气动驱动器,内层为基于主动层干扰与被动颗粒阻塞的混合阻塞变刚度层,使得软手指自动贴合被抓取对象,实现主动驱动的被动适应,并通过调整刚度实现可靠抓取。基于传统缝纫工艺,采用超弹性硅胶材料制造软手指。采用Euler-Bernoulli梁理论和虚功原理,建立了基于悬臂梁结构下的多材料软手指的刚度控制模型,并据此提出增大整体刚度的材料筛选方法。弯曲特性实验表明软手指的弯曲性能优异。变刚度和抓取实验结果表明,混合阻塞软手指刚度增大4.6倍,建立的刚度模型最大相对误差为3.4%;在抓取对象表面粗糙度增大的条件下,软手指拉脱力仍增大17%,达到1.7 N;相较于单阻塞介质软手指,抓取成功率和承载能力均得到显著提高。

厚软土层下高层建筑长短桩复合地基承载性能研究

为了提升厚软土层下高层建筑地基的承载力,提出长短桩复合地基承载性能研究。基于地质勘测结果设计长短桩复合地基,分析其承载性状及沉降情况;利用Mohr-Coulomb模型,完成承载性能模拟。实验结果显示:在短桩和长桩桩体的单桩承载载荷最大时,沉降结果均在5.00 cm左右;楼体层高为30.00 m时,单位载荷沉降平均值为0.51 cm。所提方法能够可靠分析厚软土层的高层建筑长短桩复合地基承载性能,为厚软土层的高层建筑长短桩复合地基设计提供可靠依据。

河谷区多层软土地基强夯处治分析

文章依托高速公路多层软土地基强夯处治项目,在施工现场选取具有代表性的监测断面开展现场监测,检验河谷区多层软土地基强夯处治效果。由监测数据得出,在强夯处治和路基填筑施工阶段,地基分层沉降、土压力、孔隙水压力和侧向位移增幅均较大,工后逐渐趋于稳定,可说明强夯处治后软基承载力得到有效提升,路基整体结构稳定,加固效果良好。

红层软岩崩解演化规律与强度弱化试验研究

红层软岩遇水会形成裂隙,造成岩体剥落、崩解,导致其强度降低,从而影响边坡的整体稳定性.为了探究降雨条件下红层软岩的崩解演化规律和强度弱化特性,采用干湿循环和单轴压缩试验,对软岩的崩解现象、崩解机理以及力学性能进行了分析研究,结果表明:泥岩的颗粒级配会随循环次数的增加而改变;泥岩的耐久性受干湿循环作用的影响很大;随着干湿循环次数递增,软岩的峰值强度和弹性模量逐渐下降,泊松比则呈上升趋势;红层软岩的崩解过程为:原生层面存在-水分浸润岩体-新裂隙产生以及原生层面扩展-干湿循环作用-岩体经历弱崩解、中崩解、强崩解阶段-丧失整体性,最终成为散体.干湿循环对软岩造成的劣化损伤作用具有累积性和不可逆性,且前期劣化效果更为显著.蓬莱镇组红层软岩在成分、结构、构造等方面与其它地区红层不同,导致了崩解的差异性.研究可为红层软岩地区因降雨引起的岩体强度损失折减程度进行判定.

Numerical Analyses of Caisson Breakwaters on Soft Foundations Under Wave Cyclic Loading

A caisson breakwater is built on soft foundations after replacing the upper soft layer with sand. This paper presents a dynamic finite element method to investigate the strength degradation and associated pore pressure development of the intercalated soft layer under wave cyclic loading. By combining the undrained shear strength with the empirical formula of overconsolidation clay produced by unloading and the development model of pore pressure, the dynamic degradation law that describes the undrained shear strength as a function of cycle number and stress level is derived. Based on the proposed dynamic degradation law and M-C yield criterion, a dynamic finite element method is numerically implemented to predict changes in undrained shear strength of the intercalated soft layer by using the general-purpose FEM software ABAQUS, and the accuracy of the method is verified. The effects of cycle number and amplitude of the wave force on the degradation of the undrained shear strength of the intercalated soft layer and the associated excess pore pressure response are investigated by analyzing an overall distribution and three typical sections underneath the breakwater. By comparing the undrained shear strength distributions obtained by the static method and the quasi-static method with the undrained shear strength distributions obtained by the dynamic finite element method in the three typical sections, the superiority of the dynamic finite element method in predicting changes in undrained shear strength is demonstrated.

双层软组织缝合封闭技术在下颌骨中早期药物相关性颌骨骨坏死患者手术治疗中的应用

目的:探究双层软组织缝合封闭技术在单纯应用抗骨吸收药物引起的发生在下颌骨的中早期药物相关性颌骨骨坏死(medication-related osteonecrosis of the jaw,MRONJ)患者手术治疗中的临床应用效果。方法:选择2021年10月至2022年9月于北京大学口腔医院四病区经手术治疗的中早期下颌骨MRONJ患者的病历资料进行回顾性分析,收集患者术前基线临床资料,包括原发疾病、伴发疾病、用药方案(药物种类、用药时长)、MRONJ分期、临床症状、影像学表现等,所有患者在手术中行下颌骨边缘切除术去除坏死骨,运用双层软组织缝合封闭技术关闭伤口,术后定期复查随访,评价双层软组织缝合封闭技术的治疗效果及并发症,并对患者进行疼痛评分和功能状态评价。结果:研究共纳入13例患者(女12例,男1例),年龄(66.69±13.14)岁。原发疾病包括骨质疏松7例,肺癌2例,乳腺癌3例,前列腺癌1例;2例伴发糖尿病,2例伴发心血管疾病,1例伴发干燥综合征。9例患者静脉注射唑来膦酸,平均用药时间(37.7±20.0)个月,7例患者同时服用了来曲唑片等其他药物;3例患者应用地舒单抗注射液,平均用药时间(10.3±11.9)个月;5例患者服用阿仑膦酸钠片,平均用药时间(55.20±27.20)个月,2例患者不同程度地服用醋酸泼尼松片或阿卡波糖片。MRONJ 1期4例,2期9例。13例患者均采用双层软组织缝合封闭技术关闭伤口,术后平均随访11.9个月(9~17个月),13例患者皆治愈,无溢脓等并发症发生。患者术前Karnofsky功能状态评分量表(Karnofsky performance status,KPS)评分为(68.46±14.05)分,术后评分为(82.31±15.36)分,差异有统计学意义(P<0.05)。患者术前疼痛评估视觉模拟评分量表(visual analogue scale,VAS)评分为(5.77±0.73)分,术后评分为(0.38±0.51)分,差异有统计学意义(P<0.001)。结论:双层软组织缝合封闭技术在中早期单纯使用抗骨吸收类药物的下颌骨MRONJ患者中可以取得良好的临床治疗效果,可为用药情况更加复杂的MRONJ患者提供临床治疗思路。

长期连作茭白增加水田深层土壤有机碳的积累

为了解长期连作茭白后水稻土有机碳库及其组分的变化,选择了连续种植茭白时间分别为0(对照)、2~5、5~10、10~20、20~30、30~35 a等6组种植茭白前土壤类型相同的18块农田,通过挖掘标准土壤剖面采集0~20、20~40、40~60、60~80 cm分层土样,分析了土壤有机碳、不同稳定性有机碳组分和微生物生物量碳。结果表明:随着茭白种植时间的增加,土壤容重由上层至下逐渐下降;各土层中有机碳总量、高活性有机碳、中活性有机碳、低活性有机碳和惰性有机碳及微生物生物量碳均逐渐增加,增幅以20~40、40~60 cm等2个土层最为明显。同时,深层土壤中高活性有机碳比例呈现显著的增加,20~80 cm土层中有机碳总量及其各形态有机碳贮量占0~80 cm土层有机碳总量的比例逐渐增加,呈现有机碳向深层土壤积累的特点。分析认为,深耕、长期浸水及茭白生产过程田间人为频繁踩踏,导致土壤犁底层逐渐消失、软糊层形成是造成茭白田深层土壤有机碳快速积累、有机碳活性增加的主要原因。

水平层状软岩大断面小净距隧道关键施工技术研究

结合工程实例,围绕水平层状软岩大断面小净距隧道关键施工技术展开探讨。首先介绍了隧道的主要工程背景。其次分别介绍了隧道单侧壁导坑法施工和双侧壁导坑法施工的详细施工流程与施工要求,并提出应急预案处治措施,结合隧道特点,提出了隧道施工过程中应具体监控量测的内容。最后从施工安全设计方面提出具体针对措施,可为同类型隧道项目提供借鉴。

复杂周边环境下的深基坑支护及开挖施工技术优化

为探究复杂周边环境下的深基坑支护及开挖施工技术优化问题,首先,通过对深基坑周边复杂环境、工程特点和工程难点进行重点分析,提出切实可行的保障措施。其次,基于复杂环境下的深基坑施工重难点,对基坑支护和开挖方式进行优化,并通过有限元分析软件进行施工过程模拟,提出相关施工技术优化方向。最后,对基坑支护和开挖过程进行自动化监测,确保对周边建构筑物产生的影响在可控范围内。

双排桩-锚索支护体系在软土地区基坑中的应用

为研究双排桩-锚索结构在软土基坑中的内力变化规律及可行性,本文通过理论计算及数值模拟,以东莞某软土基坑工程为例,对结构水平位移、弯矩等参数的变化规律进行了研究,并将实测值与计算值进行了对比。结果表明,卸荷板可提供一个反弯矩,增加结构稳定性;支护结构水平位移理论及数值计算曲线与实测曲线变化趋势基本相似,变形值均在规范允许范围之内;双排桩-锚索结合卸荷板体系应用于场地受限的软土地区基坑支护效果较好。

改进YOLOv5的无人机航拍图像密集小目标检测算法

无人机航拍图像中小目标实例多、尺寸变化剧烈且存在密集遮挡等问题,为解决现有目标检测算法难以检测到航拍图像中的小目标物体,提出了一种针对密集小目标的RDS-YOLOv5检测算法。在YOLOv5的三个检测层上新增一个小目标检测层,以保留更丰富的特征信息,增强网络对小目标特征的提取能力,并改善误检漏检情况;为了提高网络的多尺度特征表征能力以及抑制冲突的产生,设计了具有等级制的残差结构的多尺度特征提取模块C3Res2Block;使用解耦检测头Decoupled Head避免不同任务之间的差异所带来的预测偏差,提升了模型的定位精度和检测精度;采用软化非极大值抑制Soft NMS算法对候选框的置信度进行优化,提高模型对密集小目标的检测精度。通过VisDrone数据集的实验结果表明,与基准模型YOLOv5相比,RDS-YOLOv5在mAP0.5上提升了12.9个百分点,mAP0.5:0.95上提升了10.6个百分点,与目前主流的目标检测算法相比也取得更优的检测精度,能够有效完成无人机航拍图像的密集小目标检测任务。

饱和软土非平行等效时间线流变一维固结分析

在饱和软土非平行等效时间线流变模型基础上,综合考虑软土地基成层性和非线性特点,利用半解析法对地基一维固结控制方程进行求解分析。采用Fortran语言编制相关计算程序,将退化后的计算结果与已有的平行等效时间线下的流变固结解进行对比,验证该解答的正确性。利用该程序分析饱和软土地基流变固结性状,分析讨论了非平行线参数ζ对土体次固结系数的影响,以及非平行等效时间线流变固结下有效应力定义的固结度和地表总沉降的增长规律。分析结果表明:非平行等效时间线模型的次固结系数随自重应力和有效应力的增大而减小,且减小速率取决于ζ值大小;非平行等效时间线下的流变特性主要对主固结后期和次固结阶段影响显著,ζ值越大,主固结完成越早,后期次固结沉降量越小。