Construction controlling and strength increasing characteristics of locally developed epoxy asphalt mixture

The construction controlling elements,including construction performance at low ambient temperatures,reserved time ranges,and the strength increasing rule,for locally developed epoxy asphalt mixture（LDEAM） are studied through laboratory tests.Air void and Marshall stability are chosen as the performance measures for evaluating the construction quality.The wheel rolling test is used to simulate the actual construction situations,while the Marshall test and the Brookfield viscosity test are adopted to study the strength increasing rule.The experimental results reveal that the LDEAM can be constructed under a low ambient temperature condition of 10℃,and its longest reserved time is 70 min at a reserved temperature of 120℃.Test also shows that the strength of the LDEAM increases with time and temperature before cured.Finally,the theoretical reason for the strength increasing rule is analyzed on the basis of the organic chemistry theory.

Status quo and Development Strategies for Protected Vegetable Industry in Qinghai Province

The study introduced protected agriculture development in Qinghai province and concluded its development scale, type and structure, as well as technology supports. Besides, existing problems were proposed such as lower production-level, poor equipment, fewer specialized bases, and countermeasures include the following： leading protected agriculture development by macro-control; strengthening market supervision; improving scientific research and innovation to help S ＆ T achievement transformation.

Investigation of cost-effectiveness of highway asphalt pavement maintenance treatments based on rutting development analysis

To investigate the cost-effectiveness of different maintenance treatments of highways in Jiangsu Province, the historical pavement maintenance records, traffic load information and pavement performance data in the pavement management system （PMS） are recorded and analyzed. Compared with the growth model, the linear model, the logarithm model and the exponential model, the cubic model has higher regression accuracy R2 and it can capture the sigmoid shape of the deterioration curve. So it is selected to simulate the pavement rotting development. The benefit over cost ratio is calculated to quantify the treatment cost- effectiveness. The analysis results show that thin hot mix asphalt （HMA） overlays and micro surfacing are more cost- effective than the. other two treatments on light and moderate traffic roads. Hot in-place recycling and thick HMA overlays have much longer service lives and greater cost-effectiveness under heavy or extra heavy traffic.

Numerical analysis on thermal regime of wide embankment in permafrost regions of Qinghai-Tibet Plateau

This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment section of Qinghai-Tibet highway,computational region for numerical analysis was defined.And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data.The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling.Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing.And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment.Raising embankment height can improve the thermal stability; however,the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing.Thus,to construct expressway with wide embankment in permafrost regions of Qinghai-Tibet Plateau,effective measures need to be considered to improve the thermal stability of underlying permafrost.

Soil Depletion

Soils are under threat around the world. Erosion, pollution, salinization and acidification degrade soils irreversibly. Evidently, the rate of soil degradation greatly exceeds the rate of soil formation. In some countries, soil lost is almost 100 times faster than the rate of its formation. Therefore, soil needs to be considered as a nonrenewable resource. Incessant construction activities along with unsustainable mining operations and energy-related undertakings in recent years have accelerated the degradation of soil in Turkey. Highway travellers can witness the mindless plunder all over the land. As one travels smoothly on newly constructed highways, looming along the roads are piles of leftover destruction： heaps of broken asphalt from previous roads; newly excavated topsoil dumped into adjacent streams; eroded hillsides. In the age of global climate change, these so-called development efforts sound incomprehensible since such anthropogenic activities exacerbate the change. Clearly, climate change increases the erosion rates and reduces the soil quality. This fact alone requires each country to adopt and implement sound conservation practices to protect their soils, and hence, social stability and security. The most effective way to conserve soil is to establish and maintain ground cover vegetation. Avoiding unnecessary soil sealing also conserves soil.

Effect of Traffic Speed on Stresses and Strains in Asphalt Perpetual Pavement

Increasing traffic volumes and loads as well as public expectation for a long-lasting transportation infrastructure have necessitated designing perpetual pavements. The KDOT （Kansas Department of Transportation） conducted a field trial to investigate the suitability of perpetual pavement concept for Kansas highway pavements. The experiment involved construction of four thick pavement structures. To verify the approach of designing perpetual pavements on the basis of an endurance strain limit, the pavements were instrumented with gauges for measuring tensile strains at the bottom of asphalt base layers at various speeds. Pavements were also instrumented with pressure cells to measure stress on the top of subgrade. Pavement response measurements under known vehicle load were performed in August 2006. FWD （Falling-weight deflectometer） was also used to collect deflection data at 15 m intervals on the same date. FWD first-sensor （center） deflections were normalized and corrected to 20 ℃ temperature based on measured mid-depth pavement temperature. The result shows that strain and stress measurements show significant amount of variations. Measurements in the thickest section are the most consistent. The higher the traffic speed, the lower the strains and stresses. The difference between strains and stresses at 30 kmhar and 65 km/hr is higher than the difference between 65 km/hr and 95 kin/hr. This shows the effect of speed on stresses and strains decreases as the speed increases. Softer binder in the asphalt base layer results in lower strains, which confirms that softer binder results in higher fatigue life.

Innovate Project Supervision System for Higher Engineering Construction Quality

With rapid development of PetroChina＇s Qinghai Oilfield, engineering construction quality becomes more and more important in infrastructure construction of the oilfield. Generally speaking, engineering construction quality is related both to national economic development and safety of people and assets. To turn a design map into a materialized object, the construction project involves a large number of elements, such as design, materials, machinery, landform, geological factors, meteorological factors, construction process, technological measures and supervision system. Therefore, quality control holds the key to a construction project.

大连——发展中的魅力

为了推动在辽宁的各国留学生更好地学习汉语,增进他们对辽宁的了解,辽宁省有关部门举办了枫叶杯“我和辽宁”外国留学生汉语演讲比赛。来自全省各大专院校的各国留学生从心底里流淌出一曲曲优美的旋律,充分表达了他们对辽宁、对中国的感人的心声。他们的演讲打动了所有听众。本栏目特摘登两篇作品以飧读者。本刊也欢迎来华留学生学习汉语的习作,或反映他们在中国学习、生活的故事。

Relationships between altitudinal gradient and plant carbon isotope composition of grassland communities on the Qinghai-Tibet Plateau,China

Foliar and root carbon isotope composition(δ13C) of grassland communities on the Qinghai-Tibet Plateau,China,was obtained by the biomass weighting method and direct measurement.We investigated the characteristics and altitudinal patterns of foliar and root δ13C and determined which environmental factors influenced foliar δ13 C most.Foliar δ13 C of alpine steppe was significantly higher than that of alpine meadow and temperate steppe.For alpine meadow,root δ13C was significantly higher than of foliar δ13C.Foliar δ13C increased with altitude at an average rate of 0.60‰ km 1 for the whole grassland ecosystem.This rate was lower than that at species level.However,there were no significant relationships between root δ13C and altitude.Atmospheric pressure was a more important factor than temperature and precipitation in its influence on the altitudinal pattern of foliar δ13C at the community level.