A FINITE ELEMENT DOUBLE POROSITY MODEL FOR HETEROGENEOUS DEFORMABLE POROUS MEDIA

The mathematical base of the double porosity concept, consisting of the continuity and equilibrium equation respectively, is briefly reviewed. A quasi-steady-state transfer function, the so-called leakage term, is used. Important aspects of the developed code, based on the double porosity theory, are presented together with two hypothetical example problems. The resulting trend of the settlements are compared to those from previous work and was found to be significantly different. However, the implications are that the present study exhibits a more realistic prediction for the settlement.     

细砂中钢带-填土废塑料瓶抗拔性能试验研究

研究利用填土废塑料瓶作为横向构件附在加筋土挡墙（MSEWs）中钢带上可行性。配筋中的横向构件对增加抗拔力有重要影响。该加筋系统是由作为纵向构件的钢带和作为横向构件的填土废塑料瓶组成。为更好地研究以填土废塑料瓶作为横向构件对抗拔性能的影响,对一条独立的钢带和分别带有1～7个瓶子的钢带进行了拉拔试验。在不同的法向应力下进行了超过18次的实验室大型拉拔试验（例如拉拔箱尺寸为长1.2 m、宽0.6 m、高1.0 m）来评估新提出的加固元件的性能。试验结果表明,在扁钢带上建立三维空间对提高抗拔阻力影响很大。提高抗拔阻力最有效的方法是在距离S与直径D之比为3的钢带上加入4个横向构件,其平均抗拔阻力约为单独钢带的5倍。有横向构件和无横向构件钢带的极限抗拔阻力随竖向应力的增大而增大。     

Diagenetic and Depositional Impacts on the Reservoir Quality of the Upper Jurassic Arab Formation in the Balal Oilfield,Offshore Iran

The Kimmeridgian‐Tithonian aged Arab Formation, as the main reservoir of the Jurassic succession in the Balal oilfield, located in the offshore region of the Iranian sector of the Persian Gulf, is investigated in this study. The formation is composed of dolomites and limestones with anhydrite interbeds. Based on detailed petrographic studies, six microfacies are recognized, which are classified in four sub‐environments including supratidal, intertidal, lagoonal and the high energy shoal of a homoclinal carbonate ramp. The main diagenetic features of the studied succession include dolomitization, anhydritization, cementation, micritization, fracturing and compaction. Based on stable isotope data, dolomitization of the upper Arab carbonates is related to sabkha settings (i.e. evaporative type). In terms of sequence stratigraphy, three shallowing‐upward sequences are recognized, based on core and wireline log data from four wells of the studied field. Considering depositional and diagenetic effects on the reservoir quality, the studied facies are classified into eight reservoir rock types (RRT) with distinct reservoir qualities. Dolomitization has played a major role in reservoir quality enhancement, whereas anhydritization, carbonate cementation, and compaction have damaged the pore throat network. Distribution of the recognized RRTs in time and space are discussed within the context of a sequence stratigraphic framework.     

新疆博斯腾湖东岸盐渍土分布特征

新疆焉耆盆地博斯腾湖东岸几种不同地貌单元中,盐渍土发育强烈。在研究区内自北至南50km的地段呈线性分布。以刻槽法分5层连续采取0～1．00m深度土壤样品,分析易溶盐含量,判断盐渍土的含盐类型。平面上,从冲洪积扇前缘的细土平原到冲积-湖积平原,盐渍化程度呈增高趋势。盐渍土的含盐类型,沙垅段主要为硫酸盐,东南岸冲积-洪积平原主要发育亚硫酸盐和硫酸盐,其余地段盐渍土类型以氯盐和亚氯盐为主。剖面上,除沙垅段外,各个地貌单元土壤盐渍化表聚性特征明显。     

Petrogenesis of Mafic Garnet Granulite in the Lower Crust of the Kohistan Paleo-arc Complex (Northern Pakistan): Implications for Intra-crustal Differentiation of Island Arcs and Generation of Continental Crust

We report the results of a geochemical study of the Jijal andSarangar complexes, which constitute the lower crust of theMesozoic Kohistan paleo-island arc (Northern Pakistan). TheJijal complex is composed of basal peridotites topped by a gabbroicsection made up of mafic garnet granulite with minor lensesof garnet hornblendite and granite, grading up-section to hornblendegabbronorite. The Sarangar complex is composed of metagabbro.The Sarangar gabbro and Jijal hornblende gabbronorite have melt-like,light rare earth element (LREE)-enriched REE patterns similarto those of island arc basalts. Together with the Jijal garnetgranulite, they define negative covariations of La_N, Yb_N and(La/Sm)_N with Eu^* [Eu^* = 2 x Eu_N/(Sm_N + Gd_N), where N indicateschondrite normalized], and positive covariations of (Yb/Gd)_Nwith Eu^*. REE modeling indicates that these covariations cannotbe accounted for by high-pressure crystal fractionation of hydrousprimitive or derivative andesites. They are consistent withformation of the garnet granulites as plagioclase–garnetassemblages with variable trapped melt fractions via eitherhigh-pressure crystallization of primitive island arc basaltsor dehydration-melting of hornblende gabbronorite, providedthat the amount of segregated or restitic garnet was low (<5wt %). Field, petrographic, geochemical and experimental evidenceis more consistent with formation of the Jijal garnet granuliteby dehydration-melting of Jijal hornblende gabbronorite. Similarly,the Jijal garnet-bearing hornblendite lenses were probably generatedby coeval dehydration-melting of hornblendites. Melting modelsand geochronological data point to intrusive leucogranites inthe overlying metaplutonic complex as the melts generated bydehydration-melting of the plutonic protoliths of the Jijalgarnet-bearing restites. Consistent with the metamorphic evolutionof the Kohistan lower arc crust, dehydration-melting occurredat the mature stage of this island arc when shallower hornblende-bearingplutonic rocks were buried to depths exceeding 25–30 kmand heated to temperatures above c. 900°C. Available experimentaldata on dehydration-melting of amphibolitic sources imply thatthickening of oceanic arcs to depths >30 km (equivalent toc. 1·0 GPa), together with the hot geotherms now postulatedfor lower island arc crust, should cause dehydration-meltingof amphibole-bearing plutonic rocks generating dense garnetgranulitic roots in island arcs. Dehydration-melting of hornblende-bearingplutonic rocks may, hence, be a common intracrustal chemicaland physical differentiation process in island arcs and a naturalconsequence of their maturation, leading to the addition ofgranitic partial melts to the middle–upper arc crust andformation of dense, unstable garnet granulite roots in the lowerarc crust. Addition of LREE-enriched granitic melts producedby this process to the middle–upper island arc crust maydrive its basaltic composition toward that of andesite, affordinga plausible solution to the ‘arc paradox’ of formationof andesitic continental-like crust in island arc settings. KEY WORDS: island arc crust; Kohistan complex; Jijal complex; amphibole dehydration-melting; garnet granulite; continental crustal growth