Fluid flow in cataclastic thrust fault zones in sandstones, Sub-Andean Zone, southern Bolivia

The Bolivian Sub-Andean Zone (SAZ) corresponds to a Neogene thrust system that affects an about 10-km thick Palaeozoic to Neogene siliciclastic succession. The analysis of macro and microstructures and cement distribution in thrust fault zones shows that they are sealed by quartz at depths >3 km, due to local silica transfer by pressure-solution/precipitation activated at temperatures >70–90 °C. At shallower depths, faults have remained open and could be preferential drains for lateral flow of carbonate-bearing fluids, as shown by the occurrence of carbonate cements in fractures and their host-sandstone. Due to decreasing burial, resulting from foothill erosion during fault activity, critically buried fault segments can be affected by non-quartz-sealed structures that post-date initial quartz-sealed structures. The integration of textural, fluid inclusion and isotopic data shows that carbonates precipitated at shallow depth (<3 km), low temperature (<80 °C) and relatively late during the thrusting history. Isotopic data also show that precipitation occurred from the mixing of gravity-driven meteoric water with deeper formation water bearing carbonate carbon derived from the maturation of hydrocarbon source rocks (Silurian and Devonian shales). The combined microstructural and isotopic analyses indicate that: (i) fluid flow in fault zones often occurred with successive pulses derived from different or evolving sources and probably related to episodic fault activity, and (ii) at a large-scale, the faults have a low transverse permeability and they separate thrust sheets with different fluid histories.     

南方膨胀土的微结构特性与工程性质研究

本文对南方膨胀土的微结构特性进行了实验研究,表明膨胀土具有其特殊的微结构特性,其决定着膨胀土的膨胀势。而膨胀土的膨胀性能决定于微结构特性——水体系(内因)与外界环境因素的有机组合。     

扩展传统的岩石锚固技术

主要介绍了膨胀锚杆的锚固性能。这种锚杆不仅可以用于硬岩，而且还可以在不适合其它锚杆的条件下加以应用。     

膨胀土的矿物组成与膨胀特性关系的试验研究

介绍了用χ射线衍射法、热分析和次甲基兰－氯化亚锡定量蒙脱石等方法，对采自我国十省的膨胀土进行了矿物组成特性方面的试验研究。并讨论了它们与膨胀土的膨胀势等的关系     

膨胀土地区旋挖钻进埋钻事故的处理方法及预防措施

就旋挖钻机在膨胀土地层进行钻孔灌注桩施工时发生桩孔大面积坍塌埋钻事故的处理方法和后期钻孔灌注桩施工预防措施进行介绍。     

武汉地铁三号线土层盾构开挖引起的地表沉降研究

为了研究红黏土的变形特性,使用常规固结仪和自制收缩仪,对压实桂林红黏土进行了无荷载条件下4次膨胀和收缩试验。结果表明:红黏土的胀缩变形过程是不可逆的;随着干湿循环次数增加,膨胀试验试样高度变化较小,收缩试验试样高度逐渐增大,膨胀变形和收缩变形均呈逐渐减小趋势;稳定后膨胀率和收缩率均逐渐减小,收缩系数不断减小,最终趋于一个较稳定数值;采用绝对膨胀率、绝对收缩率、相对膨胀率、相对收缩率等参数可以定量分析干湿循环作用下压实红黏土的胀缩变形程度及其变化规律。     

膨胀力变化规律试验研究

对膨胀土胀缩机理进行了阐述,剖析了膨胀力概念,指出GB/T50279-98界定的膨胀力为最大膨胀力或极限膨胀力,提出自然膨胀力概念及其试验方法。首次开展了自然膨胀力随增湿程度变化规律的试验研究,并对膨胀力随增湿程度、干密度大小、起始含水率等因素的变化规律以及等同土样进行不同程度脱湿后的膨胀力变化规律开展了试验研究,得到了诸多有价值的结论,使对膨胀力概念的认识更加深入,其应用也更符合工程实际。     

重塑膨胀土的三向膨胀力试验研究

用三向胀缩仪对南阳陶岔重塑膨胀土做了12个三向膨胀力试验,9个湿胀干缩试验和9个控制变形的膨胀力试验。试验结果表明,三向膨胀力不等,水平膨胀力小于竖向膨胀力;湿胀干缩使重塑膨胀土的膨胀力降低,第一次干湿循环后膨胀力减小最多;微小的位移可以使膨胀力大大降低,膨胀力与位移呈对数关系;给出了膨胀力与初始含水率和干密度的关系式。     

On the compression behavior of remolded cement-admixed soft clay

Although extensive research has been performed on the mechanical properties of cement-stabilized clays, quite a few attempts have been made on the compression behavior of remolded cement-admixed clays. The results from oedometer tests have been discussed to investigate the compressibility of remolded cement-admixed clays, taking into consideration cement amount and curing time. The findings show that the difference in shape and position of compression curves is attributed to cement amount and curing time. Most compression index (C_c) values of remolded cement-admixed clays are greater than those of untreated clay due to the presence of remolded yield stress σ′_yr that is closely related to initial water content and clay fabric. Based on the obtained test data, the relationships of C_c vs. e₀, C_c vs. w₀, C_c vs. e₁, C_c vs. e_yr, and σ′_yr vs. e_yr are preliminarily discussed and quantitatively established. Especially, an important divergence of void index I_v at effective stress σ′_v less than remolded yield stress σ′_yr can be observed at different cement amounts and curing durations. Being independent on cement amount, curing time, and initial state of soil, an excellent convergence occurs at stress σ′_v greater than yield stress σ′_yr. The normalized compression curves of I_v vs. σ′_v at σ′_v?>?σ′_y can be expressed by a unique line that agrees well with intrinsic compression line (ICL) and extended ICL.     

Bacterial methane in the Atzbach-Schwanenstadt gas field (Upper Austrian Molasse Basin), Part I: Geology

Bacterial methane gas accumulations occur in Upper Oligocene to Early Miocene clastic deepwater sediments in the Austrian Molasse Basin. Methane gas is produced from the Upper Puchkirchen Fm. (Aquitanian) in the Atzbach-Schwanenstadt gas field which is one of the largest gas fields in this basin.