蒙脱土基材料在锂金属电池中的应用研究进展

锂金属电池作为下一代高能量密度电池的代表,近年来受到了广泛的关注和研究。然而,锂金属电池的商业化应用依然面临着重大的挑战,如锂枝晶的不可控生长和电解质界面稳定性差导致电池的循环性能较差,甚至引发严重的安全问题。蒙脱土因其独特的结构,大的比表面积以及良好的热稳定性,有望用于锂金属电池中来提高其电化学性能。因此,在锂金属电池中引入蒙脱土基材料被认为是解决上述问题最有效的方法之一。综述了用于高性能锂金属电池的蒙脱土基材料、改性策略等相关研究进展,并对其未来发展进行了展望。

骨料特性对土基流动性回填材料流动度影响研究

粉土基可控性低强度材料(土基CLSM)是低碳绿色回填材料的一个发展方向。本研究以等粒径大小分别为0.5mm、1mm、2mm、5mm、10mm玻璃珠为理想骨料,探讨以粉土和水为胶凝剂配制土基CLSM的可行性,研究等粒径玻璃骨料粒径、含量与水固比对土基CLSM流动性的影响。结果表明,试验范围所有粒径理想骨料均可配置符合施工流动度要求的CLSM。所有骨料粒径的土基CLSM均表现出随水固比增加而流动度增大。良好流动度水固比与骨料含量有关,与骨料粒径无关。低掺量骨料流动度受土基流动性控制,良好流动度对应的水土比与纯土相同。高掺量骨料符合施工要求的流动度均出现泌水现象,对应的水土比与纯土出现泌水现象时的水土比一致。基于骨料堆积结构对试验结果进一步分析,发现优势骨料掺量为40%~50%。

土基柠条强化材料的抗压性能试验研究

柠条由于其木质纤维强度和韧性均远优于其它灌木,可作为加筋材料,有效提高土墙的抗压强度。为此,采用完全析因试验设计,以沙壤土和黏土两种不同的土基材料、柠条的加筋长度、质量加筋率为试验因子,对土基柠条强化材料进行无侧限抗压强度试验,测定其极限抗压强度、屈服强度、压缩模量和伸长率等主要力学指标。在此基础上,对不同的土基材料进行了对照比较分析,运用SAS软件对不同的因子进行了多响应完全随机设计的方差分析,并对试验数据进行了多元回归分析。试验结果表明:相同因子水平下,黏土柠条强化材料的抗压强度明显优于沙壤土柠条强化材料对应的强度;在0~6mm的柠条长度范围内,土基柠条强化材料的抗压强度与柠条长度成正相关关系;当柠条的质量加筋率为0.25%时,黏土柠条强化材料的抗压强度达到最大。该研究结果为柠条可再生资源在绿色建筑材料方面的应用提供了基础。

Flexural behaviors of steel reinforced ECC/concrete composite beams

An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increase the ductility and crack resisting ability of the beam. Based on the assumption of the plane remaining plane and the simplified constitutive models of materials, the stress and strain distributions along the depth of the composite beam in different loading stages are comprehensively investigated to obtain calculation methods of the load-carrying capacities for different stages. Also, a simplified formula for the ultimate load carrying capacity is proposed according to the Chinese code for the design of concrete structures. The relationship between the moment and curvature for the composite beam is also proposed together with a simplified calculation method for ductility of the ECC/RC composite beam. Finally, the calculation method is demonstrated with the test results of a composite beam. Comparison results show that the calculation results have good consistency with the test results, proving that the proposed calculation methods are reliable with a certain theoretical significance and reference value.

Comparison between responses of reinforced and unreinforced embankments due to road widening

The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional(2D) finite element(FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement,horizontal displacement,pore water pressure,and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small,it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.

Foundation Assessment in Different Parts of Iraq Using STAAD Pro V8i

Foundation is considered as one of the main parts of any structure. The type of foundation used is highly dependent on the type and properties of soil. The design of foundations requires many factors that should be defined. There are number of differences in the geological and soil conditions in Iraq. As a consequence, these differences are reflected on the type of foundation to be used. Despite these differences, same materials and style of buildings are used all over Iraq. The main problems of Iraqi soil are high gypsum content, salinity and shallow water table depth. These factors that influence the foundations are the soil properties and the amount of loads that transmitted by the superstructure. The situation has been analysed through a case study which illustrated the link between soil and foundation types in three different parts of Iraq （Mosul, Baghdad and Basra）. One building was analysed using ＂STAAD （structural analysis and design）. Pro＂ software in these regions. It is evident that Iraqi designers and engineers require local code to define all the loads, materials and design of the foundation to be used. The use of local materials might be very effective from both engineering and economic perspectives.

Stress and deformation due to embankment widening with different treatment techniques

A two-dimensional(2-D) finite element(FE) model was developed to analyze the deformation and stress of embankment on soft ground due to widening with different treatment techniques.It is found that the embankment widening induces transverse gradient change due to differential settlements and horizontal outward movements at the shoulder of the existing embankment.Embankment widening also increases the shear stress along the slope of the existing embankment,especially at the foot of slope.The failure potential due to embankment widening may increase with the increase of widening width when the widening width is smaller than 8.5 m,but may decrease with the increase of widening width as the widening width is greater than 8.5 m.The effectiveness of four ground and embankment treatment techniques,including geosynthetic reinforcement,light-weight embankment,deep mixed columns,and separating wall were compared.The results indicate that these treatments reduce the differential settlements and improve the stability.The light-weight embankment has the most effectiveness among four treatments.By using the fly-ash backfill material in widening,the transverse gradient change decreases from 0.5%-1.3% to 0.26%-0.8% and the maximum horizontal displacement decreases from 2.76 cm to 1.44 cm.

Experimental and theoretical research on residual strength of plain concrete under compressive fatigue loading

To investigate the residual strength of concrete under fatigue loading, experiments were conducted to determine the functional relation between residual strength and the number of cycles. 80 100mm×100mm×100mm specimens of plain concrete were tested under uniaxial compressive fatigue loading. Based on probability distribution of the residual strength of concrete under fatigue loading, the empirical expressions of the residual strength corresponding to the number of cycles were obtained. There is a good correlation between residual strength and residual secant elastic modulus. Thus the relationship between residual secant elastic modulus and the number of cycles is established. A damage variable based on the longitudinal maximum strain is defined, and a good linearity relationship between residual strength and damage is found out.

Vertical drainage capacity of new electrical drainage board on improvement of super soft clayey ground

As an advanced polymer composites electro-kinetic geosynthetics, the electro-osmotic vertical drainage(EVD) board could drain water quickly and accelerate consolidation process. However, the drainage rate was mainly impacted by the vertical drainage capability. Therefore, vertical drainage capability at the top of EVD board was theoretically analyzed. Basic requirements for drainage at the top of the board were summed up, as well as the formula of anode pore pressure when losing the vertical drainage capability. Meanwhile, a contrast test on the top and bottom drainage capacities was conducted. In use of the advanced EVD board, the voltage potential and pore pressure of anode were measured. Moreover, the derived formulas were verified. The result shows that the decrease of electric force gradient had an observable impact on the drainage capability. There was nearly no difference between the energy consumption for the two drainage methods. Although a little less water was discharged, the top drainage method had more advantages, such as high initial drainage velocity, few soil cracks, low anode water content and high soil strength. All of these show that the super soft soil ground could be consolidated quickly in use of the advanced EVD board through the top drainage. The top drainage method could efficiently improve the drainage effect, decrease the energy consumption and speed up the project proceeding.

Flexural response of reinforced concrete beams strengthened with post-poured ultra high toughness cementitious composites layer

Four-point bending tests were conducted up to failure on eleven reinforced concrete (RC) beams and strengthening beams to study the effectiveness of externally pouring ultra high toughness cementitious composites (UHTCC) on improving the flexural behavior of existing RC beams.The strengthening materials included UHTCC and high strength grade concrete.The parameters,such as thickness and length of strengthening layer and reinforcement in post-poured layer,were analyzed.The flexural behavior,failure mode and crack propagation of composite beams were investigated.The test results show that the strengthening layer improves the cracking and ultimate load by increasing the cross section area.Introducing UHTCC material into strengthening not only improves the bearing capacity of the original specimens,but also disperses larger cracks in upper concrete into multiple tightly-spaced fine cracks,thus prolonging the appearance of harm surface cracks and increasing the durability of existing structures.Compared with post-poured concrete,UHTCC is more suitable for working together with reinforcement.The load?deflection plots obtained from three-dimensional finite-element model (FEM) analyses are compared with those obtained from the experimental results,and show close correlation.

Bearing capacity and settlement of strip footing on geosynthetic reinforced clayey slopes

The effect of geosynthetic reinforcing on bearing capacity of a strip footing resting on georeinforced clayey slopes was investigated.The results of a series of numerical study using finite element analyses on strip footing upon both reinforced and unreinforced clayey slopes were presented.The objectives of this work are to:1) determine the influence of reinforcement on the bearing-capacity of the strip footings adjacent slopes,2) suggest an optimum number of reinforcement and 3) survey the effect of friction angle in clayey soils reinforced by geogrids.The investigations were carried out by varying the edge distance of the footing from slope.Also different numbers of geosynthetic layers were applied to obtaining the maximum bearing capacity and minimum settlement.To achieve the third objective,two different friction angles were used.The results show that the load?settlement behavior and ultimate bearing capacity of footing can be considerably improved by the inclusion of reinforcing layer.But using more than one layer reinforcement,the ultimate bearing capacity does not change considerably.It is also shown that for both reinforced and unreinforced slopes,the bearing capacity increases with an increase in edge distance.In addition,as the soil friction angle is increased,the efficiency of reinforcing reduces.

Seismic response analysis of GRPS embankment under oblique incident P wave

In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary(VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.

Seismic behaviors of steel reinforced ECC/RC composite columns under low-cyclic loading

To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.

Effects of Different Substrate Composition on Growth of Gesneriaceae Plants

The cultivation experiment was carried out to investigate the effects of dif-ferent proportions of peat soil, perlite, vermiculite and yel ow mud on growth of Gesneriaceae species （Chirita gueilinensis, Sinningia speciosa, Lysionotus pauci-florus, Hemiboea henryi, Aeschynanthus acuminatus, Saintpaulia ionantha）. The growth traits of each plant growing in 7 different matrix materials were investigated. The plant height, crown width and chlorophyl content of each plant were mea-sured. The results showed that the best substrate ratio was peat soil∶vermiculite=2∶1 for C. gueilinensis, L. pauciflorus and H. henryi; peat soil∶perlite∶vermiculite = 2∶1∶1 for S. ionantha; peat soil∶vermiculite∶yel ow mud=2∶1∶1 for S. speciosa; peat soil∶per-lite∶vermiculite∶yel ow mud=2∶1∶1∶1 for A. acuminatus.

Preliminary Evaluation of Some Engineering Properties of Laterite as Foundation and Construction Materials in Muglad Basin in Sudan

This paper reports and evaluates the subsurface investigations of lateritic soil in Muglad Basin. Lateritic soil is described as highly weathered and altered residual/transported soil formed by the in-situ weathering and/or decomposition of rocks in the tropical and sub-tropical regions with hot, humid climatic conditions. The field works include excavation of test pits, drilling of boreholes and performing of SRT （standard penetration test）. The engineering properties of soil such as sieve analysis, consistency, compaction test, CBR （California bearing ratio） test are deduced in the laboratory. Lateritic soil is also evaluated to be used as foundation and construction materials. Concretionary lateritic soil is valuable road pavement materials, widely used in the tropics as sub-base, base material and for gravel roads. The term laterite, however, has tended to be indiscriminately applied in tropical highway engineering to any red soil. Lateritic soils in this study area were classified as reddish brown, medium dense to very dense, clayey silty sand with noodles of quartz and gravels. According to laboratory test, the lateritic soil was found to be good as construction materials, and can be used for embankment purposes; on the other hand, blending such materials with gravels can improve the low CBR values.

Amendment of Acid Soils with Crop Residues and Biochars

The liming potential of some crop residues and their biochars on an acid Ultisol was investigated using incubation experiments. Rice hulls showed greater liming potential than rice hull biochar, while soybean and pea straws had less liming potential than their biochars. Due to their higher alkalinity, biochars from legume materials increased soil pH much compared to biochars from non-legume materials. The alkalinity of biochars was a key factor affecting their liming potential, and the greater alkalinity of biochars led to greater reductions in soil acidity. The incorporation of biochars decreased soil exchangeable acidity and increased soil exchangeable base cations and base saturation, thus improving soil fertility.

Effects of nanoclay addition on the permeability and mechanical properties of ultra high toughness cementitious composites

Tuning microstructures by adding nanoparticles is a promising way of improving the performance of cementitious composites.In this study,nanoclay was introduced to polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composites(UHTCCs).The mechanical properties,crack patterns,water permeation resistance,and microstructures of UHTCCs with different dosages of nanoclay were studied.The addition of a proper dosage of nanoclay shows few effects on the compressive strength of UHTCCs,however,the compressive strength is decreased when an excessive amount of nanoclay is added.The flexural deformation capacity of UHTCCs is independent of nanoclay dosage,whereas the flexural strength generally decreases with an increasing dosage of nanoclay.Different cracking patterns were observed in the ultra high toughness cementitious composites containing nanoclay(NC-UHTCC)specimens subject to bending tests.A UHTCC with 1%(in weight)nanoclay shows the best water permeation resistance and the lowest water permeability.Variations in the mechanical properties and the water permeation resistance of UHTCCs containing different dosages of nanoclay could be ascribed to the synthetic effects of filling and heterogeneous nucleation of nanoclay at low dosages and the agglomeration effect of nanoclay at high dosages.This study is to optimize the water permeation resistance of UHTCCs,paving a path for the future application of UHTCCs in the fields of construction,decoration,and repair.

Field study on performance of new technique of geosynthetic-reinforced and pile-supported embankment at bridge approach

Vehicle bumps at a bridge approach caused by the differential settlement between a bridge and an adjacent backfill embankment are one of the most difficult problems in geotechnical engineering. Large vehicle bumps make drivers uncomfortable and cause large impact loads on vehicles and the bridge abutment. A new ground-improvement technique called fixed-geosynthetic-reinforced and pile-supported embankment(FGT embankment) was developed and used to alleviate vehicle bumps at a trial bridge-approach site located in central China. To distribute the differential settlement between the bridge and adjacent backfill embankment over a long transition zone, the following three techniques were used at the trial bridge-approach site:(a) the FGT embankment,(b) conventional geosynthetic-reinforced and pile-supported embankment(CT embankment), and(c) geosynthetic-reinforced embankment without piles(GR embankment). The performance of all three techniques in the field trial was investigated by field measurements involving earth pressure cells, geosynthetic deformation sensors, and settlement gauges. The FGT and CT embankments exhibited better performance than the GR embankment. Compared with the CT embankment, the FGT embankment was more effective at ground improvement. At an elevation of 4.0 m from the base of the embankment, the pressures below the geosynthetic were smaller than those above the geosynthetic at the closest measurement point. The difference between the pressures between above and below the geosynthetic tended to increase with the embankment height.

Seismic behavior of precast concrete coupled shear walls with engineered cementitious composite (ECC) in the critical cast-in-place regions

The seismic performance of precast reinforced concrete （RC） coupled shear walls is significantly influenced by coupling beams and the beam-to-wall joints during large deformations into plastic ranges. This study investigated the use of engineered cementitious composite （ECC） in the cast-in-place beam-to-wall joints and the upper regions of the composite coupling beams as an innovative method to improve the seismic performance ofprecast RQ coupled shear walls. Two 1/2-scale precast coupled shear walls were tested under reversed cyclic loading and seismic behavior in terms of failure characteristic, mechanical characteristic value, load-displacement hysteresis curves, load-displacement envelope relationship, stiffness degradation, ductility and energy dissipation capacity were evaluated. Research results show that the substitution of concrete with ECC in the critical cast-in-place regions proved to be an effective method to improve the seismic performance of the two-story spatial of precast RC coupled shear walls.

Numerical study on flexural behaviors of steel reinforced engineered cementitious composite(ECC) and ECC/concrete composite beams

Engineered cementitious composite(ECC)is a class of high performance cementitious composites with pseudo strain-hardening behavior and excellent crack control capacity.Substitution of concrete with ECC can largely reduce the cracking and durability problems associated with brittleness of concrete.In this paper,a simplified constitutive model of the ECC material was applied to simulate the flexural behaviors of the steel reinforced ECC and ECC/concrete composite beams with finite element method.The simulation results are found to be in good agreement with test results,indicating that the finite element model is reasonably accurate in simulating the flexural behaviors of the steel reinforced ECC flexural members.The effects of the ECC modulus,ECC tensile ductility,ECC thickness and ECC position on flexural behaviors in terms of ultimate moment,deflection and the maximum crack width of the steel reinforced ECC or ECC/concrete composite beam are hence evaluated.