超厚混凝土墙顶板的施工技术

以无锡美中嘉和肿瘤医院直线加速器机房的超厚混凝土墙顶板施工为例,为确保直线加速器区域的混凝土能够达到设计的抗辐射标准,通过模板支撑体系的合理设计、配合比的科学优化以及施工过程中的质量控制措施,达到了预期的效果,可为类似工程参考。     

超厚大跨度无梁顶板支撑体系的研究与应用

以太原市某地下人防指挥工程为例,对超厚大跨度无梁顶板支撑体系进行了研究,并根据工程特点,对2.1 m与4 m厚的顶板模板支撑体系采用碗扣式钢管脚手架和加强带构造措施施工方法,形成了具有可操作性及经济性一体的模架支撑体系,可对以后类似的工程提供可靠的施工技术和方案。     

大体积钢筋混凝土结构施工技术

某医院直线加速器机房墙体最大厚度为2.7 m、顶板最大厚度为2.8 m,针对大体积混凝土容易出现裂缝、超厚墙体及顶板支撑承载力、刚度、稳定性具有很高要求等特点,根据设计要求及现场条件,采取一系列施工措施,保证了混凝土施工质量。     

大跨地铁站顶模支撑体系设计及混凝土施工工艺

北京地铁15号线马泉营站为双岛四线车站,采用单柱双跨结构形式,顶板跨度15.75 m,横断面厚度1.0～2.0 m,顶板支撑体系设计及混凝土施工难度大,因此按常规方法进行顶板支撑体系计算后又使用Midas软件进行了验算,并对混凝土施工工艺做了详细介绍。     

无缝大体积混凝土施工技术

普仁医院加速器机房为超厚钢筋砼结构.本文针对其特点、难点制定超重模板支撑方案和大体积砼施工方案,阐明墙体模板对拉螺栓钢管支撑的加固措施,顶板模板满堂碗扣架支撑体系.用优化配比、合理选材、原材预冷、分层浇筑等措施进行防裂.     

直线加速器机房防辐射大体积混凝土的施工

湖北省十堰市太和医院科技大楼,主体11层,局部13层,总建筑面积17000m2,建筑总高度52.5m,为框剪结构.在其底层东南角建有18MeV医用直线加速器机房,机房平面尺寸14.20m×10.90m,高度7.80m.为有效保证医护及周围人员的健康,机房必须要进行严格的防辐射屏蔽.该机房墙、顶板采用普通混凝土进行射线辐射的防护.     

直线加速器机房钢筋混凝土施工技术

云南省红十字会医院医技楼为框剪结构．地下室内设计有直线加速器机房,针对该机房墙面、顶板截面较厚的钢筋混凝土以及密封性能要求高的特点．在施工中重点解决支撑系统、模板系统、铜筋绑扎和混凝土一次浇筑成型等问题,保证了施工质量。该机房自建成使用至今,未发生辐射源泄漏现象。     

放射治疗室施工裂缝控制

一、工程概况浙江省东阳市人民医院肿瘤放射治疗机房位于住院大楼西北角,内置有能输出高能(兆伏级)X射线的医用电子直线加速器,机房面积尺寸21.4m×12.4m,高度5.00m。为有效保护医护人员的健康,机房必须进行严格的防辐射屏蔽,基础采用钢筋混凝土阀板基础,墙体和顶板采用防辐射重混凝土,机房主射线方向重混凝土墙厚2300mm,副射线方向混凝土墙厚1500mm,顶板板厚2500mm,属超厚大体积混凝土,工艺要求砼不允许出现贯穿裂缝,需严格控制砼体内的温度,防止有害温度裂缝的产生。二、温度裂缝的原因分析1、温度裂缝产生的原因分析从混凝土内外温差来…     

明挖车站大跨度无柱弧形顶板模架体系设计及施工技术

郑州机场至许昌市域铁路工程(郑州段)港区北站车站站厅层公共区采用大跨度无柱弧形顶板结构,结构净跨18.3 m,拱高9.0 m,矢高5.05 m。弧形顶板支撑体系设计及施工难度较大,现场施工采用了一种拼装桁架拱模架结构,论文从设计思路、模板支撑设计、模架体系受力验算及模架体系及混凝土施工对此模架支撑体系的设计及施工工艺进行详细介绍。     

超高、超重现浇钢筋混凝土楼板模板支撑体系设计与施工技术

北京奥林匹克公园(B区)国家会议中心工程超高、超重顶板共计13个部位,层高为7.8m～39.8m不等。在该部位顶板模板施工中成功应用了碗扣式钢管脚手架支撑体系,整个施工过程中未出现任何安全及质量事故。     

移动荷载下弹性半空间地基上矩形薄板的动力响应解析研究

基于三维弹性理论,先对位移表示的地基动力方程进行Laplace变换,再进行双重傅里叶变换,获得直角坐标系下弹性半空间地基受任意竖向动荷载作用下的Laplace变换域中的位移解析表达式;然后对地基上有限大矩形薄板的边值问题进行Laplace变换,并求得地基板的Laplace变换域中的含有未知地基反力的挠度解析解;最后结合板与地基的变形协调方程,完全求得弹性半空间地基板在移动荷载作用下的Laplace变换域中的解析解。在此基础上,利用Laplace数值逆变换得到地基板时间域内的动力响应。算例结果表明本文的研究方法是切实可行的。用该文方法可精确分析地基板在任意移动载荷作用下的动力特性。     

Nitrogen transformations and greenhouse gas emissions from a riparian wetland soil: an undisturbed soil column study

Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO₂ and N₂O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO₃⁻ L^− 1 solution (rate: 90 mL day^− 1) for 125 days at two different temperatures (10 and 20 °C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO₃⁻ concentration, NH₄⁺ concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO₂ and N₂O) were determined in the undisturbed soil columns. The A horizon at 20 °C showed the highest rates of NO₃⁻ removal (1.56 mg N-NO₃⁻ kg⁻¹ DW soil day^− 1) and CO₂ and N₂O production (5.89 mg CO₂ kg⁻¹ DW soil day^− 1 and 55.71 μg N-N₂O kg⁻¹ DW soil day^− 1). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO₃⁻ ha^− 1 year^− 1, and potential greenhouse gas emissions of 5620 kg CO₂ ha^− 1 year^− 1 and 240 kg N-N₂O ha^− 1 year^− 1.     

Feasibility of using U to reconstruct close-in fallout deposition from the Hiroshima atomic bomb

The first results on the feasibility of using ²³⁶U to reconstruct the level and spatial distribution of close-in fallout deposition from the Hiroshima A-bomb are reported, coupled with the use of global fallout ¹³⁷Cs and ^239 + 240Pu. The results for global fallout ²³⁶U in soil samples (0-30 cm) from Ishikawa prefecture showed that the deposition density of ²³⁶U from the global fallout can be accurately evaluated using AMS. All deposited ²³⁶U, ¹³⁷Cs and ^239 + 240Pu appeared to have been recovered using 30-cm cores. It was also noted from the depth profiles for ²³⁶U/^239 + 240Pu and ²³⁶U/¹³⁷Cs ratios that the downward behavior of ²³⁶U in the soil was apparently similar to that of ^239 + 240Pu, while the ¹³⁷Cs was liable to be retained in upper layers compared with ²³⁶U and ^239 + 240Pu. The accumulated levels were 1.78 × 10¹³ atoms m^− 2 for ²³⁶U, 4340 Bq m^− 2 for ¹³⁷Cs and 141 Bq m^− 2 for ^239 + 240Pu. The ratios of ²³⁶U/¹³⁷Cs and ²³⁶U/^239 + 240Pu were (4.10 ± 0.12) × 10⁹ and (1.26 ± 0.04) × 10¹¹ atoms Bq^− 1, respectively. Results of ²³⁶U, ¹³⁷Cs and ^239 + 240Pu measurements for the seven soil cores (0-30 cm) from Hiroshima were discussed on the basis of ratios of ²³⁶U/¹³⁷Cs and ²³⁶U/^239 + 240Pu by comparing with those from the background area in Ishikawa, indicating that the global fallout dominates the current level of ²³⁶U accumulation in soil in the Black-rain area around Hiroshima after the Hiroshima bomb, and the contribution of the close-in fallout ²³⁶U produced by the Hiroshima A-bomb seems difficult to observe.     

Phosphate removal in agro-industry: Pilot- and full-scale operational considerations of struvite crystallization

Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89 ± 3% and 75 ± 8%, resulting in final effluent levels of 12 ± 3 mg PO₄³⁻-P L⁻¹ and 11 ± 3 mg PO₄³⁻-P L⁻¹, respectively. In contrast, poor phosphate removal (19 ± 8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca²⁺/PO₄³⁻-P molar ratio (ca. 1.25 ± 0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca²⁺ interference. A shift in the influent Ca²⁺/PO₄³⁻-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78 ± 7%, corresponding with effluent levels of 14 ± 4 mg P_total L⁻¹ (9 ± 3 mg PO₄³⁻-P L⁻¹). Under these conditions high quality spherical struvite crystals of 2-6 mm were produced.     

Photolytic reaction mechanism and impacts of coexisting substances on photodegradation of bisphenol A by Bi2WO6 in water

Bi₂WO₆ displayed great photolytic degradation efficiency to bisphenol A (BPA) under simulated solar light irradiation but its reaction mechanism and the impacts of coexisting substances on the degradation remain unclear. In present study, the reaction mechanism was investigated using DMPO spin-trapping ESR spectra and experiments with scavengers of hydroxyl radicals (OH) and holes. The results supported that hole oxidation mainly governed the photodegradation process. As a common humic substance in natural water, humic acid accelerated the degradation of BPA when its concentration was 1 mg/L, while the photodegradation was impeded with the increase of humic acid concentration in the range of 5-20 mg/L. Almost all anions, including NO₃⁻, HCO₃⁻, Cl⁻, SO₄²⁻ inhibited the degradation of BPA by Bi₂WO₆ and their inhibition effects followed the order of SO₄²⁻ > Cl⁻ > HCO₃⁻ > NO₃⁻. Cations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ displayed slight suppressing effect on BPA degradation mainly due to the impact of Cl⁻ coexisting in the solution. However, Cu²⁺ hindered the BPA photodegradation heavily. Fe³⁺ and H₂O₂ affected the photodegradation in a complicated way: they suppressed or promoted the photodegradation depending on their concentrations. This could be the result of competition between photolyitc hole generated by Bi₂WO₆ and OH produced by Fe³⁺ or H₂O_2.