贺兰山北段孔兹岩系脱水熔融实验Ⅱ--岩石结构对变质反应的制约

贺兰山北段孔兹岩系中最有代表性的两类岩石 :变粒岩及富铝片麻岩天然块状样品的脱水熔融实验研究表明 ,在不同的温度压力条件 ,两类岩石产生明显不同的变质反应 ,其中变粒岩类在所有的实验条件下均产生 Bt+Pl+Qz→ Hy+Kf+M(熔体 )的反应 ,而富铝片麻岩在不同压力下出现不同的变质反应 :0 .4 GPa条件下发生 :Bt+Pl+Qz→ Hy+Kf+M;0 .6 GPa条件下发生 :Bt+Qz→ Sil+Kf+M;0 .8GPa条件下发生 :Bt→ Cud+Kf+M。本文认为制约变质反应的主要因素是岩石的结构构造 ,因此在讨论高级变质作用时更要强调压力的重要性     

山岭隧道堵水限排围岩力学特性分析

为了尽可能减少隧道长期大量排水带来的严重环境问题,高水位地区的深埋山岭隧道应采取“以堵为主,限量排放”即“堵水限排”的防排水设计准则。但在堵水限排情况下围岩的力学特性如何？是当前隧道衬砌结构设计急需解决的关键问题之一。首次建立了山岭隧道堵水限排情况下围岩力学特性分析的解析模型并进行了理论推导,分析了不同排水工况下围岩力学特性的变化并绘制了相应的围岩特征曲线,为堵水限排衬砌结构设计提供了理论依据。     

锚索桩的主动支护作用及桩身初始内力分析

预应力锚索桩在桩身施工完毕且锚索施加了初始预应力时,因滑坡推力未及作用于桩上,初始预应力即刻对受荷段桩背的岩土体产生迎滑动方向反推的一种主动支护效应,同时使桩身产生初始内力。基于受荷段桩背岩土水平反力模数为常数的单向Winkler弹性地基梁模型,以及嵌入段桩周岩土水平反力双参数模式的Winkler弹性地基梁模型,以受荷段桩身挠曲线的有限差分式与嵌入段挠曲线的解析通解改进式在滑面处的协调条件联立,推导了锚索初始预应力所产生主动支护效果的半解析定量计算和桩身初始内力求解方法,该方法有助于建立应急抢险或施工期,锚索桩工程对滑坡稳定性及时作用的评估。     

锦屏二级水电站引水隧洞长期稳定性数值分析

针对锦屏II水电站深埋引水隧洞高地应力、强渗透压的复杂赋存环境及硬脆性岩体的特点,采用凝聚力弱化-摩擦强化（CWFS）模型反映岩体的脆塑性变形特点。采用黏弹性模型反映其黏性变形规律,基于现场的位移监测资料,通过遗传规划和粒子群算法的流变模型及参数识别方法得到黏弹脆塑性流变模型及其参数,利用大型岩土工程分析软件FLAC3D,模拟了隧洞群岩体的流变力学行为、喷锚支护型式及其与围岩相互作用机制以及工程结构体在高渗透压下的流固耦合效应。通过模拟结果的分析,采用位移、位移速率、应力、破坏接近度及支护结构的受力状况等状态信息的综合集成分析方法,对此工程围岩及结构体在复杂赋存环境中的长期稳定性状态进行了评价,并论证了现有设计方案的合理性,为指导工程设计和施工起到重要的作用。     

桩锚结构预应力的变形协调确定方法

目前,对于如何确定桩锚结构锚索预应力并没有统一的理论,通过对现有的预应力锚索抗滑桩设计中确定锚索预应力值的各种方法的分析研究,提出了一种确定预应力的方法,即把锚索、抗滑桩与周围的岩土体作为一个整体,根据长期作用荷载找出使桩身受力较为合理情况下的锚索总拉力,即桩身正负弯矩基本相等时锚索上的拉力,充分考虑桩锚协调变形条件进行锚索预应力的计算,并以某高速公路互通区一滑坡为例,与其他方法进行对比分析,证明所提出的方法在桩身受力方面更为合理,能更好地发挥桩锚结构体系的作用。     

长期重复荷载作用下土体与邻近桩基相互作用研究

在前人研究的基础上,基于临界状态土力学理论,在Carter模型中引入临界重复应力的概念形成改进Carter模型;该模型概念明确、参数简单,可以合理地反映重复加卸载作用下土体主要特性。利用改进Carter模型,编制平面应变有限元程序,对长期重复加卸载作用下土体与临近桩基相互作用进行系统分析,探讨了长期重复加卸载作用下有桩和无桩时土体沉降和侧移的变化规律,并讨论了软土屈服面衰减系数、临界重复应力水平、临近桩基刚度等变化时桩土相互作用性状的变化,得出一些有益的结论。     

考虑孔压积累-消散耦合的等效有限元方法

交通荷载往复作用下饱和软土路基会发生显著的工后沉降,并引起不均匀沉降。采用基于室内循环三轴或空心圆柱扭转试验建立的经验显式模型与等效有限元相结合方式,在预测路基长期沉降方面取得了较好的效果。然而,其采用的瞬时积累、逐步消散的孔压模型与实际工程中孔压积累与消散同时进行有着明显的差异。忽略这种差异将会使得计算结果低于实际值。采用能反映自然排水条件下震动孔压长消规律的解析公式,对以上的不足作出改进,并用改进的孔压模型计算了上海浦东国际机场第一跑道的长期运营沉降。分析表明,与瞬时积累、逐步消散的孔压模型相比,考虑孔压积累与消散耦合效应的孔压模型,计算结果更接近实测资料。     

Analysis on long-term change of sea surface temperature in the China Seas

Long-term change of sea surface temperature (SST) in the China Seas from 1900 to 2006 is examined based on two different observation datasets (HadISST1 and HadSST3). Similar to the Atlantic, SST in the China Seas has been well observed dur-ing the past 107 years. A comparison between the reconstructed (HadISST1) and un-interpolated (HadSST3) datasets shows that the SST warming trends from both datasets are consistent with each other in most of the China Seas. The warming trends are stronger in winter than in summer, with a maximum rate of SST increase exceeding 2.7℃ (100 year)-1 in the East China Sea and the Taiwan Strait during winter based on HadISST1. However, the SST from both datasets experienced a sudden decrease after 1999 in the China Seas. The estimated trend from HadISST1 is stronger than that from HadSST3 in the East China Sea and the east of Taiwan Island, where the difference in the linear SST warming trends are as large as about 1℃ (100 year)-1 when using respectively HadISST1 and HadSST3 datasets. When compared to the linear winter warming trend of the land surface air temperature (1.6℃ (100 year)-1), HadSST3 shows a more reasonable trend of less than 2.1℃ (100 year)-1 than HadISST1’s trend of larger than 2.7℃ (100 year)-1 at the mouth of the Yangtze River. The results also indicate large uncertainties in the estimate of SST warming patterns.     

Experimental studies of melt-peridotite reactions at 1–2 GPa and 1250–1400°C and their implications for transforming the nature of lithospheric mantle and for high-Mg signatures in adakitic rocks

Experiments of the melt-peridotite reaction at pressures of 1 and 2 GPa and temperatures of 1250–1400°C have been carried out to understand the nature of the peridotite xenoliths in the Mesozoic high-Mg diorites and basalts of the North China Craton,and further to elucidate the processes in which the Mesozoic lithospheric mantle in this region was transformed.We used Fuxin alkali basalt,Feixian alkali basalt,and Xu-Huai hornblende-garnet pyroxenite as starting materials for the reacting melts,and lherzolite xenoliths and synthesized harzburgite as starting materials for the lithospheric mantle.The experimental results indicate that:(1)the reactions between basaltic melts and lherzolite and harzburgite at 1–2 GPa and 1300–1400°C tended to dissolve pyroxene and precipitate low-Mg#olivine(Mg#=83.6–89.3),forming sequences of dunite-lherzolite(D-L)and duniteharzburgite(D-H),respectively;(2)reactions between hornblende-garnet pyroxenite and lherzolite at 1 GPa and 1250°C formed a D-H sequence,whereas reactions at 2 GPa and 1350°C formed orthopyroxenite layers and lherzolite;and(3)the reaction between a partial melt of hornblende-garnet pyroxenite and harzburgite resulted in a layer of orthopyroxenite at the boundary of the pyroxenite and harzburgite.The reacted melts have higher MgO abundances than the starting melts,demonstrating that the melt-peridotite reactions are responsible for the high-Mg#signatures of andesites or adakitic rocks.Our experimental results support the proposition that the abundant peridotite and pyroxenite xenoliths in western Shandong and the southern Taihang Mountains might have experienced multiple modifications in reaction to a variety of melts.We suggest that melt-peridotite reactions played important roles in transforming the nature of the Mesozoic lithospheric mantle in the region of the North China Craton.