Major element geochemistry of purple soils/rocks in the red Sichuan Basin, China: implications of their diagenesis and pedogenesis

Major element compositions and chemical weathering features of the purple soils and their corresponding rocks in the Red Sichuan Basin, China were studied in this paper to infer the diagenetic features of the purple rocks and the pedogenetic features of the purple soils. The results showed that all of the rock and soil samples, except those from Yibin, have strongly similar major element compositions and the distribution patterns of their major element compositions are similar to those of the upper continental crust. Chemical index of alteration, chemical index of weathering and Na₂O/K₂O indicate that the purple soils and rocks have similar chemical weathering intensities, whereas the Al₂O₃–CaO* + Na₂O–K₂O (A–CN–K) relationship, suggests that chemical weathering was strong during diagenesis of the purple rocks, but weak during pedogenesis of the purple soils. Variations in major element compositions of the purplish rock samples, except that from Yibin, do not primarily reflect differences in compositions of the sediment source, sediment recycling and potassium metasomatism, and therefore the effects of chemical weathering on the major element compositions were mainly dependent on climate condition and the residence time of material exposed to chemical weathering. Chemical weathering of the purple rocks reached only moderate degrees under the general influence of warm and humid climate during Jurassic and Cretaceous. Warmer and more humid climate conditions partly resulted in stronger chemical weathering of rocks in the southern region of the basin than in the central and western region, whereas shorter residence time of material in upslope position partly resulted in weaker chemical weathering of rocks in the eastern region than in the central and western region. The same climate and stable tectonic setting led to comparable chemical weathering intensities of rocks in the Ziliujing and Jiaguan Formations. Gradually colder and dryer climate from Early Jurassic to Middle Jurassic then to Late Jurassic and shorter residence time in tectonically active setting of Middle Jurassic and late Late Jurassic resulted in the following order of chemical weathering intensity of the purple Jurassic rocks: Ziliujing Formation ? Shaximiao Formation ≈ Suining Formation > Penglaizhen Formation.     

动物体内青石棉纤维变化特征的显微研究

石棉纤维粉尘注入动物体内后，一部分形成石棉小体或石棉斑，一部分仍为裸露纤维。石棉小体内的纤维表面基团和组织内的某些蛋白反应可形成新的表面介体。粉尘在动物体内引起的动物病变主要是纤维化组织包裹和间皮瘤，机体以吞噬、包裹、缠绕，或以生化溶解方式排解粉尘。纤维自身则出现变短、尖部圆化、折断、分叉现象，也可以出现溶解、迁移、表面化学反应等。肺泡内纤维的碳酸盐化现象是体内纤维溶解和反应的新方式。动物体内间皮瘤可生长在注入部位也可在非注入部位，某种毒性衍生物质的生成和迁移是引起病变的主要原因。体内纤维粉尘的溶解是一个非常缓慢的过程，细小粉尘易于溶解和迁移。体内粉尘的膜阻滞现象在腹膜、胸膜上较为常见，在膜部位不易生成间皮瘤，肿瘤多引发在膜的内侧。但膜可以弱纤维化包裹。     

桩筏基础下地基土的荷载传递特性

桩筏基础由桩和筏组成一种联合基础，筏将大部分总荷载传递给桩，同时其本身也承担总荷载的一部分。因此，充分认识桩筏基础对上部荷载向地基土的传递特性是非常必要的。该文提出一个桩筏基础传递荷载的计算模型，模型考虑了桩的布置形式对地基接触压力的影响，同时还考虑了桩的受荷过程中的变化特性，并详细分析了桩与筏之间的荷载分配问题。     

地质灾害与地层岩性的关系探讨

通过对福建省内10余个县（市）地质灾害调查与区域综合研究分析。认为各种地质灾害的发生与地质体的母岩有着内在联系,不同类型地质体母岩所发生地质灾害的种类、机率和形成规模也不尽相同。基于福建省现有地质灾害数据库所采集的资料,就地质灾害与地质体母岩的影响关系进行初步探讨。     

强胁迫力使脆弱环境突变——松辽平原百年开发史例证

以松辽平原为案例,首次提出并论证了"人类强胁迫力作用于脆弱环境系统必将导致生态环境突变"的命题。而这种突变机理又对"人类力是现代环境变化的第一驱动力"的论点提供支持。文章运用了区域学原理,对区域综合要素进行了分析,判定区域属于脆弱系统;运用地理景观理论,构建了距今约150年、100年、50年和现今(2000年)共4个时期的区域生态景观模型,揭示出人类逐阶强化胁迫的过程,并结合遥感分析,首次识别出松辽平原大面积荒漠和半荒漠;引进系统突变模型,论证了生态环境突变过程的存在及所特有的快速扩张性,可导致重大生态灾难--荒漠化过程失控。文章建议应认真研究中国广大地带的环境突变问题,制定科学合理的环境战略,应对全球环境变化的挑战。     

基于贝叶斯网络的地下水环境系统决策管理研究

应用贝叶斯网络解决地下水环境管理中具有不确定性的多目标决策问题,通过对决策变量氮肥施用量以及灌溉模式的调控,减少水中的硝酸盐含量,达到既能有效改善水环境又不至使农民经济利益受到损害的目标。通过分析具体的地下水环境管理系统中变量间的相互关系,构建描述变量间不确定性关系的贝叶斯网络模型,其中包括表示其依赖关系的有向无环图和表示其具体概率依赖程度的条件概率表。并在多个水环境管理目标均达到最优的前提下进行概率推理,得到决策变量氮肥施用量以及灌溉模式取不同值时目标变量的概率分布情况。最终确定出能使所有目标均达到最优的合理的水环境管理决策:(1)使用喷灌,将氮肥施用量控制在0.01~0.03 kg/m2;(2)使用漫灌,将氮肥施用量控制在0.01~0.02 kg/m2。     

对蓬安县三元水库大坝外坡裂缝产生的原因及整治工程的探讨

本文通过对蓬安县三元水库大坝外坡裂缝产生的原因分析,进而运用岩、土力学的理论与方法反算推论出了裂缝的产生不是深层坝体土滑动引起的,而是局部浅层坝体土在水的诱发作用下作蠕滑-拉裂变形所产生的。在明确了大坝裂缝产生的原因后,提出了一系列相应整治工程措施,以达到彻底根治裂缝和稳固大坝的目的。     

The nonlinear hydrodynamic model for simulating a ship steering in waves with autopilot system

In the paper, a hydrodynamic numerical model including wave effect is developed to simulate ship autopilot systems by using the time domain analysis. The PD controller and the sliding mode controller are adopted as the autopilot systems. The differences of simulation results between two controllers are analyzed by cost function composed of heading angle error and rudder deflection, either in calm water or in waves. The results in calm water show that both controllers are tracking well for the desired route with the similar cost function value by tuning the key design parameters. However, the course tracking ability of the controller using sliding mode in waves is generally better even the cost function value is similar.     

Numerical analysis and centrifuge modeling of shallow foundations

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.