二氧化碳储存环境对油井水泥性质影响之研究

二氧化碳存入地下以地质封存方式进行减量是一项可行的工程手段。干燥情况下二氧化碳基本没有危害。然而在进行地质封存时,气井通常在地下水层、盐水层等潮湿的环境下操作,二氧化碳与水结合会形成碳酸,形成一个酸性的环境。实验室将API G级油井水泥添加包括飞灰、膨润土、重晶石与硅粉,在潮湿(100%)、饱和二氧化碳（常压,70 ℃）环境条件下养护28 d,研究其力学性能、化学成分及微观结构之间的关系。试验项目包括抗压强度、微观结构分析、X射线衍射及EDS扫描电镜。观察其养护样品发现,API G级添加飞灰的水泥呈现出最佳抗压强度及最深的碳化深度。而API G级添加膨润土的水泥现出最低抗压强度及最浅的碳化深度     

油页岩原位注浆封闭浆液配方研究

油页岩在原位开采过程中,开采井与周围环境相通,原位产生的油气容易渗入周围地层形成环境污染,目前尚没有一种经济性较好的原位封闭技术来解决该难题。本文基于注浆封闭原理,通过试验探究,提出采用无污染且造价低的超细水泥注浆配方来对开采区进行封闭。经过系列配方的优化选择,最终确定优化的配方是水灰比为0.8,微硅粉掺量为6%,膨润土掺量为2%,聚羧酸减水剂掺量为0.4%,此时浆液的性能基本达到工程要求。     

铝酸钡-钙矿相体系的实验研究

以碳酸钡、碳酸钙和氧化铝为原料,设计配方在不同温度下煅烧,制备了铝酸钡-钙复相水泥.运用X射线粉末衍射(XRD)和扫描电子显微镜(SEM)等手段,对铝酸钡与铝酸钙在不同温度下的固溶过程及相转变进行了分析.结果表明:在升温过程中,首先形成大量的铝酸钡,随着温度升高,铝酸钙含量增多.同时,还出现了少量七铝酸十二钙、铝酸二钙和铝酸三钙.铝酸钡呈柱状,铝酸钡-钙固溶相主要由板状六角形或钝圆状小晶体堆积而成.     

云冈石窟砂岩中碳酸盐胶结物化学风化及相关文物病害研究

云冈石窟地区云冈组上段砂岩中碳酸盐胶结物的含量普遍在10%以上,其主要矿物成分为含铁方解石和含铁白云石。在碳酸盐胶结物化学风化过程中发生的化学反应包括碳酸盐矿物溶解、Fe2+ 离子氧化及Fe3+ 离子水解,以及石膏、泻利盐、水碳镁石、球碳镁石等矿物结晶。水、砂岩中裂隙和层理发育、大气污染等是影响碳酸盐胶结物化学风化的主要外因。碳酸盐胶结物化学风化引发了多种文物病害,对云冈石窟的文物价值造成严重破坏。      

Evaluation of Engineering and Cement–Stabilization Parameters of Clayey–Sand Mixtures under Soaked Conditions

Clay soils, especially clay soils of high or very high swelling potential often present difficulties in construction operations. However, the engineering properties of these clay soils can be enhanced by the addition of cement, thereby producing an improved construction material. Higher strength loss of cement stabilized clay soils after soaking in water is attributed to water absorbing capacity of the clay fraction (e.g. montmorillonite). Kaolinite and illitic soils are largely inert and resist to water penetration. These clays generally develop satisfactory strengths resulting to low strength reduction [Croft, 1967]. The swelling clays such as bentonite soaked in water, due to environmental conditions, result to volume increase causing macro and micro-fracturing in engineering structures. These fractures accelerate water penetration and consequently cause greater strength loss [Sällfors and Öberg-Högsta, 2002]. The water intrusion during soaking creates swelling and disrupts the cement bonds. The development of internal and external force systems in soil mass, due to soaking conditions, establish the initiation of slaking. Internal force system of a stabilized clayey soil consists of the resultant stresses established by the bonding potential of a cementing agent and the swelling potential of a clay fraction. In an effort to study this influence of soaking conditions and final absorbed water content on the stabilization parameters (cement, compaction, curing time), both unconfined compressive strength and slaking (durability) tests were carried out on two different cement stabilized clayey mixtures consisted of active bentonite, kaolin and sand.     

The behaviour of an artificially cemented sandy gravel

The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore water pressure and a barrelling failure mode. However, cemented samples and uncemented samples tested at low confining pressure (25 and 50 kN/m²) showed dilative behaviour accompanied with negative excess pore water pressure. Shear zones were formed in these samples and a clear peak in excess pore water pressure and stress ratio against strain could be observed. Test results showed that the limiting stress ratio surface for cemented samples is curved and expands as the cementation and density increase. Unconfined compression strength of cemented samples increases with increases in cementation and density as well.     

水泥混凝土路面板下脱空的一种处理方法

分析了水泥混凝土路面损坏的主要原因 ,提出了维护与补强的办法     

Two-dimensional reactive transport modeling of the alteration of a fractured limestone by hyperalkaline solutions at Maqarin (Jordan)

Two-dimensional reactive transport modeling of the Maqarin Eastern Springs site, a natural analogue for the alteration of a fractured limestone by high-pH Portland cement waters, has been performed using the CrunchFlow code. These 2D calculations included transport by advection–dispersion–diffusion along a single fracture and diffusion in the wall rock. Solute transport was coupled to mineral dissolution and precipitation. A limited sensitivity analysis evaluated the effect of different values of primary mineral surface areas, flow velocity and sulfate concentration of the inflowing high-pH solution.Major secondary minerals include ettringite–thaumasite, C–S–H/C–A–S–H and calcite. C–S–H/C–A–S–H precipitation is controlled by the dissolution of primary silicates. Ettringite precipitation is controlled by diffusion of sulfate and aluminum from the wall rock to the fracture, with aluminum provided by the dissolution of albite. Calcite precipitation is controlled by diffusion of carbonate from the wall rock. Extents of porosity sealing along the fracture and in the fracture-wall rock interface depend on assumptions regarding flow velocity and composition of the high-pH solution. The multiple episodes of fracture sealing and reactivation evidenced in the fracture infills were not included in the simulations. Results can qualitatively reproduce the reported decrease in porosity in the fractures and in the wall rock next to the fractures. Instances of porosity increase next to fractures caused by carbonate dissolution were not reproduced by the calculations.     

CFG桩在人工填土地基处理中的应用

介绍了CFG桩在人工填土地基处理中的应用情况,并对工程实践中的技术问题进行了分析和探讨。     

Coffeehouses And The Art Of Social Engagement: An Analysis Of Portland Coffeehouses

Coffeehouses have been a part of America's cultural landscape since the seventeenth century. Their fortunes have risen and fallen with the changing demand for coffee and consumer preferences. This paper examines their historic function of promoting social engagement as so‐called third places among independently owned coffeehouses in the city of Portland, Oregon. Individual coffeehouses were evaluated to determine the extent to which they provided a supportive physical environment for social engagement in which a space is transformed into a place and detailed patron behavior was recorded over a three‐week period. Few coffeehouses provided a supportive physical environment. The majority of coffeehouse patrons during the weekday and weekend ordered drinks ‘to go.’ Among those who stayed during the weekday most sat alone and worked. Coffeehouse are spaces to ‘be alone together.’ It was only on lunchtime weekends that coffeehouses were full of the sound of conversations. Further study should consider the effect of eliminating free Wi Fi and banning laptops on social engagement and whether other place attributes need to be incorporated to promote social engagement.