Ballistic behavior of plain and reinforced concrete slabs under high velocity impact

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete slabs. In this paper, we focus on the comparison of the performance of the plain and reinforced concrete slabs of unconfined compressive strength 41 MPa under ballistic impact. The concrete slab has dimensions of 675 mm × 675 mm × 200 mm, and is meshed with 8-node hexahedron solid elements in the impact and outer zones. The ogive-nosed projectile is considered as rigid element that has a mass of 0.386 kg and a length of 152 mm. The applied velocities vary between 540 and 731 m/s. 6 mm of steel reinforcement bars were used in the reinforced concrete slabs. The constitutive material modeling of the concrete and steel reinforcement bars was performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models, respectively. The analysis was conducted using the commercial finite element package Abaqus/Explicit. Damage diameters and residual velocities obtained by the numerical model were compared with the experimental results and effect of steel reinforcement and projectile diameter were studies. The validation showed good agreement between the numerical and experimental results. The added steel reinforcements to the concrete samples were found efficient in terms of ballistic resistance comparing to the plain concrete sample.     

沉箱在近距离强夯下的振动安全探索

从振动速度入手研究了强夯对沉箱的影响,通过选取一个有代表性的区域进行了试夯,确定了夯击能大小和夯击距离对沉箱振动的影响规律,进而合理选择夯击能及夯点安全距离,以保证施工的有效性和沉箱的正常使用寿命,对类似工程有很好的指导意义。     

Thermal Drying of Sewage Sludge

Over the next decade the UK will experience significant, imposed changes in the quantity of sewage sludge produced and in the means available for its disposal. Existing practices are being reappraised and new technologies are being explored to cope with a predicted 40% increase in the quantity for disposal. Thermal drying of sludge undoubtedly has a role to play in coping with this demand.
The two principal process types, i.e. direct and indirect heat application, are appraised in depth and a comparison is drawn. A case study is identified to examine the energy demands of the process, including the potential for heat recovery and for resource reuse. The environmental impact of a typical process is also examined.     

Seawater quality and microbial communities at a desalination plant marine outfall. A field study at the Israeli Mediterranean coast

Global desalination quadrupled in the last 15 years and the relative importance of seawater desalination by reverse osmosis (SWRO) increased as well. While the technological aspects of SWRO plants are extensively described, studies on the environmental impact of brine discharge are lacking, in particular in situ marine environmental studies. The Ashqelon SWRO plant (333,000 m³ d⁻¹ freshwater) discharges brine and backwash of the pre-treatment filters (containing ferric hydroxide coagulant) at the seashore, next to the cooling waters of a power plant. At the time of this study brine and cooling waters were discharged continuously and the backwash discharge was pulsed, with a frequency dependent on water quality at the intake. The effects of the discharges on water quality and neritic microbial community were identified, quantified and attributed to the different discharges. The mixed brine-cooling waters discharge increased salinity and temperature at the outfall, were positively buoyant, and dispersed at the surface up to 1340 m south of the outfall. Nutrient concentrations were higher at the outfall while phytoplankton densities were lower. Chlorophyll-a and picophytoplankton cell numbers were negatively correlated with salinity, but more significantly with temperature probably as a result of thermal pollution. The discharge of the pulsed backwash increased turbidity, suspended particulate matter and particulate iron and decreased phytoplankton growth efficiency at the outfall, effects that declined with distance from the outfall. The discharges clearly reduced primary production but we could not attribute the effect to a specific component of the discharge. Bacterial production was also affected but differently in the three surveys. The combined and possible synergistic effects of SWRO desalination along the Israeli shoreline should be taken into account when the three existing plants and additional ones are expected to produce 2 Mm³ d⁻¹ freshwater by 2020.     

强夯法加固地基机理及设计方法

近年来,随着经济的发展,我国的建筑行业也得到了迅猛的发展,对建筑施工技术的应用和设计方法也提出了新的考验.在建筑施工过程中,强夯法在加固地基方面有着重要的作用,文章就针对强夯法加固地基机理以及设计方法进行简要的探讨.     

实施民用建筑节能标准的经济和环境影响测算研究

建立了实施民用建筑节能标准的经济和环境影响测算模型.与以往的粗略估计不同,该模型将实施民用建筑节能标准与其引起的环境经济结构变化相联系,采用4个指标评价实施民用建筑节能标准的直接经济影响、5个指标评价直接环境影响、3个指标评价完全经济影响.在两种情境假定下,应用模型进行了测算.然后对模型中的主要参数和变量进行了敏感度分...     

试析采用经验公式和现场试夯的方法对强夯工程质量的控制

结合实际工程现场试夯施工,提出了应用经验公式、技术规程与现场试验相结合的方法选择强夯各施工参数.通过现场选定3～5个夯击能进行试夯,以夯沉量数据及周围隆起量大小来确定最佳夯击能,以夯沉量趋于稳定来确定夯击次数、停锤标准;利用现场埋设孔隙水压力仪,以孔隙水压力消散情况来确定夯击遍数、夯遍之间的间歇时间.根据以上确定的施工...     

爆炸挤淤填石堤坝的沉降方法研究

在爆炸挤淤筑堤施工技术得到广泛应用的同时,对于这种处于深厚淤泥、断面形状复杂的爆炸挤淤填石堤坝沉降计算的研究却进行的很少.本文以福州港可门作业区4#、5#泊位围堤工程为背景,利用PLAXIS有限元程序进行了沉降量计算,并与传统的沉降计算方法和工程实测值进行了对比分析,提出了一种适合计算深厚淤泥爆炸挤淤填石堤坝沉降的方法...     

强夯结合砂桩在软基处理中的应用

本文通过工程实例阐述了强夯结合砂桩的方法在软基处理中的应用,介绍了强夯结合砂桩进行软基处理的方案,并通过试夯区的试验检测证明了该方案的可行性。该软基处理方法取得了良好的时间效益和经济效益,对相关工程具有一定的借鉴和指导意义。     

深地下坑道衬砌结构抗局部冲击计算方法研究

 针对深部地下围岩衬砌结构的计算,假设激活的岩块为刚体,衬砌为钢筋混凝土结构,采用刚塑性不可压缩介质模型,用极限分析理论的上限方法,通过建立动力学许可速度场得到钢筋混凝土衬砌结构对岩块冲击的阻力分量。考虑纵向钢筋对震塌和贯穿的影响,根据阻抗曲线的特征,得到具有物理基础的钢筋混凝土结构的临界震塌与贯穿厚度近似计算公式。通过与经验公式的对比,验证该方法的可靠性和实用性。