Evaluation of treated and un-treated Nubia Sandstone using ultrasonic as a non-destructive technique

Deterioration factors, both “exogenous” and “endogenous”, are major sources of damaging monumental stones in Egypt. In the current study, the change state of one of the major Egyptian stones (Nubia Sandstone) is investigated and evaluated before and after consolidation by the use of wave velocity as a new method for detecting its elasticity modulus. Wave velocity propagation (Vp) is one of the most important and effective methods for estimating the durability of monumental stones without using any other harmful method as a compressive strength. This technique is usually used for a number of purposes, the first of which is the qualification of masonry building through its morphology and detection of internal defects (e.g. voids and cracks). The second is the examination of the changes of material physical properties, and the control conservation procedures. Third, it is used with some samples of Nubia sandstone for a laboratory test. The study concludes that the durability of samples increases due to the increase of material compacting as a direct result of using consolidant materials. Using the Vp as a non-destructive technique in examining monumental materials gives the same results of other harmful techniques.     

Iron precipitation in a natural CO2 reservoir: Jurassic Navajo Sandstone in the northern San Rafael Swell,UT, USA

Diagenetic iron (oxyhydr)oxide minerals are common precipitates expected in CO₂ reservoirs, and these minerals record fluid flow for application to carbon capture and sequestration (CSS). Multiple mineralogy and spectroscopy analyses on a pore to meter scale characterize a well‐exposed, lithologically controlled, iron (oxyhydr)oxides reaction front in the Jurassic Navajo Sandstone. Dolomite is the most prevalent cement (up to 23 area%), followed by only several percent or less of iron (oxyhydr)oxides, kaolinite, illite, and gypsum cements. Bulk geochemistry based on diagenetic mineralogies in the reaction front is compared with the water chemistry from nearby modern spring effluent emanating from the Navajo Sandstone to conclude that similar fluids (i.e., CO₂‐charged, saline waters containing hydrocarbons) are responsible for the precipitation. A second comparison of bulk geochemistry and diagenetic mineralogies of the reaction front with data from other abundant Navajo Sandstone concretions in the Spencer Flat region (in south central Utah) shows that reservoir fluids likely vary spatially and temporally in the porous and permeable Navajo Sandstone. CO₂ injection into porous and permeable, quartz arenite, saline aquifers will likely result in minor clay and abundant dolomite precipitation that will significantly decrease porosity.     

Consideration on the construction process and the sandstone quarries during the Angkor period based on the magnetic susceptibility

Detailed magnetic susceptibility measurement was conducted on the sandstones used for the Angkor monuments constructed in the period spanning the Preah Ko and Angkor Wat styles, and the construction process of the buildings and quarries of the sandstones was considered. Combined with the previous study on the sandstones of the Bayon style [Uchida, E., Cunin, O., Shimoda, I., Suda, C., Nakagawa, T., 2003. The construction process of the Angkor monuments elucidated by the magnetic susceptibility of sandstone, Archaeometry 45, 221–232], the magnetic susceptibility measurement revealed that there were 7 sandstone quarries corresponding to Stages I, II, III, IVa, V, VII and VIIIb during the Angkor period. The sandstones used for the monuments belonging to Stage I show average magnetic susceptibility values ranging from 1.1 to 2.3 × 10⁻³ SI units. In the Bakheng style period (Stage II), the average magnetic susceptibility of the supplied sandstones decreased gradually from around 10 to 1 × 10⁻³ SI units over time. The magnetic susceptibility range of the sandstones used for the monuments of Stage III was from 2.3 to 3.0 × 10⁻³ SI units. In the early Angkor Wat style period (IVb), the average magnetic susceptibility of the supplied sandstones increased over time, reflecting the supply of the sandstones from two different quarries, that is, the quarry corresponding to the Khleang and Baphuon style monuments (Stage IVa), with low average magnetic susceptibilities of 1.1 to 2.4 × 10⁻³ SI units, and the quarry corresponding to the main Angkor Wat style monuments (Stage V), with high average magnetic susceptibilities ranging from 2.8 to more than 4.3 × 10⁻³ SI units. The sandstones of Stage VII show low average magnetic susceptibility around 1 × 10⁻³ SI unit. The sandstones of Stage VId is a mixture of sandstones of Stages V and those of Stage VII. The sandstones with high magnetic susceptibilities are found in the monuments belonging to Stage VIIIb, reflecting the supply from the new sandstone quarry.     

龙门石窟的彩绘装饰

龙门石窟在开凿时利用丰富多彩的彩绘颜料对窟龛和造像进行了装饰,本文通过对龙门石窟现存彩绘装饰的调查和研究,初步总结了龙门石窟彩绘装饰的一些特征和规律,并就龙门石窟彩绘装饰的时代和成分等的进一步研究提出了建议。     

河南渑池石佛寺石窟调查

渑池石佛寺石窟位于豫西地区渑池县坡头乡庙下村,一般认为开凿于北齐时期,通过对石窟造像的艺术分析,以及对石窟所存的明代碑刻的分析,本文认为当开凿于北周,属河南境内唯一的一处北周时期开凿的石窟。     

Characteristics of CO2‐driven cold‐water geyser,Crystal Geyser in Utah: experimental observation and mechanism analyses

Geologic carbon capture and storage (CCS) is an option for reducing CO₂ emissions, but leakage to the surface is a risk factor. Natural CO₂ reservoirs that erupt from abandoned oil and gas holes leak to the surface as spectacular cold geysers in the Colorado Plateau, United States. A better understanding of the mechanisms of CO₂‐driven cold‐water geysers will provide valuable insight about the potential modes of leakage from engineered CCS sites. A notable example of a CO₂‐driven cold‐water geyser is Crystal Geyser in central Utah. We investigated the fluid mechanics of this regularly erupting geyser by instrumenting its conduit with sensors and measuring pressure and temperature every 20 sec over a period of 17 days. Analyses of these measurements suggest that the timescale of a single‐eruption cycle is composed of four successive eruption types with two recharge periods ranging from 30 to 40 h. Current eruption patterns exhibit a bimodal distribution, but these patterns evolved during past 80 years. The field observation suggests that the geyser's eruptions are regular and predictable and reflect pressure and temperature changes resulting from Joule–Thomson cooling and endothermic CO₂ exsolution. The eruption interval between multiple small‐scale eruptions is a direct indicator of the subsequent large‐scale eruption.     

基于仰韶水泥的砂岩石窟裂隙灌浆材料室内筛选研究

偏高岭土是高岭土经高温脱水后形成的一种高活性的人工火山灰材料,铝酸钙膨胀剂(AEA)是以一定比例的优质高铝熟料、无水石膏等无机材料共同粉磨而成的抗裂防水膨胀剂。在研究"仰韶水泥"的过程中发现,在烧料礓石水硬石灰中添加偏高岭土后,可有效提高水硬石灰结石体的强度,缺点是收缩变形较大。本研究基于对"仰韶水泥"的研究,结合砂岩石窟及其裂隙加固的特点,通过室内研究在烧料礓石水硬石灰中添加不同比例偏高岭土和膨胀剂AEA后浆液的流动性、凝结时间、收缩率、龄期强度等基本性能,初步筛选出了适宜砂岩石窟裂隙加固的灌浆材料及配比。     

砂岩文物加固材料与实验室工艺研究

风化砂岩文物的加固是文物保护的重要课题。在本研究中,选择与严重风化的云冈石窟石质文物材质相同的新鲜砂岩为研究对象,采用化学加速风化方法将石质试样进行风化模拟处理,使其风化程度接近于石窟文物本体。利用4种硅酸酯类加固材料和7种实验室工艺条件,对风化模拟石质试样进行加固处理。对处理后的石质试样进行渗透深度、色差、耐盐性、耐紫外老化、无侧限抗压强度性能测试,评估各材料与实验室工艺加固效果。经研究表明:不同材料对风化砂岩均有加固效果,其中硅酸乙酯及其低聚物材料加固作用明显;同种材料、不同实验室工艺条件下加固效果却不一样,减压浸渍法实验室工艺的加固效果最大。本工作结果将为砂岩类石质文物现场加固保护提供科学基础数据。     

南京栖霞山千佛岩石窟的测绘与编号

本文是南京栖霞山千佛岩石窟科学考察成果的第一部分。作者对千佛岩石窟进行了精确的地形测量,结合洞窟形制与窟檐的测绘、佛像的调查对洞窟进行了分区与编号,并对石窟造像的现状进行了综述。     

孟津谢家庄石窟开凿时间及艺术分析

孟津谢家庄石窟开凿于西魏大统三年,为洛阳地区最早的西魏石窟造像.其造像艺术手法带有鲜明的民间造像特点,表现出大胆浪漫的情调,具有十分重要的价值.