季节性冻土区能量桩位移变化规律

能量桩是一种既可以与土体进行能量交换,又可以承担上部荷载的桩基形式。上部土层冻结,下部土层未冻结,由温度变化引起的桩体自身变形及土体的冻胀融沉引发的桩体位移是能量桩在季节性冻土地区推广中亟待解决的主要问题。针对季节性冻土地区土体温度分布特点,将土体分为冻结层和非冻结层分别开展模型试验,测得冻结层和非冻结层中能量桩多次温度循环后的桩—土温度分布、桩周土体孔隙水压力及桩体位移的变化规律。结果表明：在非冻结土层中,多次循环取热后桩顶会产生不可逆的沉降位移,5次取热循环后,桩顶沉降达到0.95%D(D为桩体直径),且桩体沉降未达到稳定;在冻结层,放热过程中能量桩会发生桩体融沉现象,恢复过程中会发生桩体冻胀现象,融沉导致的沉降位移随着循环次数的增加逐渐减小,在第3轮放热循环后消失。第1、2、3轮的融沉位移分别为5.9%D、0.93%D、0.11%D。每轮循环过程中,冻胀引起的上升位移虽逐轮减小,但在5轮循环之后依旧存在,且冻胀引发的总位移呈阶梯状上升,桩体最终产生上升位移,达到3.8%D。     

碎石桩+CFG桩与粉喷桩在工程实例中的比较

以某工程实例为背景,对两种地基处理方案——碎石桩+CFG桩二元地基处理方法和粉喷桩处理方法进行了对比分析,并对两种地基处理方法展开了计算与费用比较,得出采用碎石桩+CFG桩的复合处理方法可以节约成本,便于施工,缩短工期。     

Investigation on the structural and microstructural properties of copper-doped hydroxyapatite coatings deposited using solution precursor plasma spraying

Structural and microstructural investigation of solution precursor plasma sprayed copper-doped hydroxyapatite coatings with different Cu dopant concentration was carried out. Scanning electron micrographs did not show any significant morphological changes at the surface and cross-section of the coatings as copper content increases. X-ray diffraction results showed the decrease in the HA phase content from 93 wt.% to 14 wt.% and its degree of crystallinity from 94% to 85% with increasing copper concentration. Raman and IR spectra revealed the broadening and red-shifting of the phosphate bands due to the distortion of the HA structure caused by possible insertion of copper. X-ray photoelectron spectroscopy identified Cu and Cu²⁺ as copper species incorporated in HA. Rietveld refinement showed an increase in the lattice a and c parameter and expansion of the unit cell volume associated to an interstitial insertion of Cu along the hexagonal channel of the HA structure.     

Dynamic and kinetic modeling of isotopic transient responses for CO insertion on Rh and Mn–Rh catalysts

Isotopic transient tracer techniques have been employed to study heterogeneous hydroformylation on Rh/SiO₂ and Mn–Rh/SiO₂. Pulse injection of D₂ and allowed tracing of the deuterium and CO incorporation pathway into the aldehyde product. The d₁- and d₂-propionaldehyde responses showed a double-peak, or two-hump, response to the D₂ pulse, while showed a single-hump response to the pulse. Analysis of the product responses to the D₂ pulse in CO/H₂/C₂H₄ and CO/H₂/C₂H₄/C₂H₅CHO suggests that the first hump of the d₁- and d₂-propionaldehyde responses was due to rapid H/D exchange with adsorbed propionaldehyde via enol intermediates. The decay of the second hump was due to reaction of adsorbed acyl with spillover hydrogen/deuterium. The response was due to CO insertion followed by acyl hydrogenation. Compartment modeling of the product responses from the and D₂ pulse inputs allowed determination of residence times of adsorbed intermediates, surface coverages of adsorbed intermediates, and the elementary rate constants for acyl hydrogenation and CO insertion. Elementary rate constants for acyl hydrogenation determined from this study were consistent with the value calculated by transition state theory (TST). The addition of Mn promoter to Rh/SiO₂ increased coverages of , , and and shifted the rate-limiting step for propionaldehyde formation. Acyl hydrogenation is the rate-limiting step on Rh/SiO₂ while CO insertion and acyl hydrogenation are both kinetically significant on Mn–Rh/SiO₂.     

静压桩承载力分析

结合东营某工程的静力压桩资料、静载试验资料及静力触探资料,计算模拟了压桩力,分析了沉桩的可能性,预估了单桩承载力并与静载试验结果进行对比,其结果令人满意,为设计和施工提供了很有价值的依据．     

分层土中群桩的竖向和摇摆动力阻抗计算

采用动力文克尔地基梁模型,在研究两桩竖向动力相互作用时,建立被动桩的运动方程,求得均匀土中竖向动力相互作用因子的解析解。在各分层土中建立单桩竖向振动微分方程,利用各分层土之间桩身的连续性条件和桩顶、桩底边界条件,求解单桩振动方程。采用三步法计算分层土中桩基竖向动力相互作用因子,结合单桩竖向动力阻抗和相互作用因子求解群桩竖向和摇摆动力阻抗。通过算例分析,得到一些有意义的结果和结论。     

西北地区城市杂填土场地的地基处理实例分析

针对如何改良软弱地基的问题,介绍了在西北地区湿陷性黄土地区杂填土场地地基处理时常用的几种方法,并分别结合具体实例分析各种地基处理方法的优缺点和适用性,以期经济合理地处理各类杂填土场地。     

预应力敞口管桩与闭口管桩的单桩沉降分析研究

通过在对8根预应力敞口管桩与闭口管桩的荷载-沉降试验,对比分析研究了敞口管桩与闭口管桩的沉降特性,并得出在桩顶荷载达到第3级荷载之前,两种桩的沉降几乎相同,随着继续加载,闭口管桩沉降与开口桩相比,沉降速度减缓,在达到管桩单桩极限承载力之前,闭口管桩沉降仅为敞口管桩的30%~50%左右.     

强风化砂岩边坡锚筋桩布置方式及支护作用研究

强风化顺层砂岩边坡具有节理裂隙发育、强度低的特征,导致开挖过程中出现边坡稳定问题。单纯的锚杆锚索支护无法满足边坡稳定性需求,在现场抗滑桩施工困难的情况下,选用经济、高效、施工便利的锚筋桩结合锚杆锚索对强风化顺层砂岩边坡进行支护。针对强风化砂岩破碎且强度低的特性,考虑高压注浆的劈裂作用,通过FLAC 3D数值模拟进行方案比选,得到适用于强风化砂岩边坡的锚筋桩多角度交叉布置方案。根据试验段边坡锚筋桩监测数据,分析强风化顺层砂岩边坡锚筋桩作用机理,验证了多角度交叉布置锚筋桩对强风化顺层砂岩边坡的加固效果。     

高稳高效海上风电安装平台关键制造技术研究

海上风电作为可再生清洁能源之一,受到世界各国的高度重视与大力发展.我国将海上风电提升至解决能源危机、减缓气候变化、调整能源结构的国家战略高度,到2030年我国单位国内生产总值二氧化碳排放将比2005年下降65％以上,非化石能源占一次能源消费比重将达到25％左右.安装平台不足将是我国海上风电场无法如期建成投产的主要障碍....