The repeated freeze-thaw cycles with seasonal alternations have an obvious effect on soil structure. To reduce the temperature sensitivity of saline soil and then use it in engineering, a combined treatment method is proposed, where lime, fly ash and modified polyvinyl alcohol (MPA) are used as solidified materials. Unconfined compressive strength (UCS) tests and microstructure characterization are firstly used to evaluate the solidified effect and obtain the parameters range of solidified materials. Then, the shear strength tests for determining cohesion and internal friction angle are conducted. Experiments are conducted by considering separate and combined treatments of materials mentioned above. The results indicate that the combined treatment with lime, fly ash and MPA can improve the strength of saline soil. After combined treatment, the UCS is 1130.25 kPa, which is 5.18 times than that of saline soil (218 kPa). The strength of combined solidified saline soil meets the requirements of engineering specification (JTG 3430-2020). The stable value of UCS of combined solidified saline soil is 700 kPa under freeze-thaw cycles. The fluctuation is about 5% after three freeze-thaw cycles. The cohesion and the internal friction angle of combined solidified saline under the optimal proportion can be 208.2 kPa and 38.56°, respectively after three freeze-thaw cycles. The sensitivity of the factors is in an order of decreasing importance: curing time, lime content, MPA content, dry density, salt content, and freeze-thaw cycles. With an increase of lime, fly ash and MPA content, the strength of combined solidified saline soil increases and then tends to become stable. The optimization of solidification parameters can effectively weaken the influence of freeze-thaw on coastal saline soil. Based on tests results of compressive strength and shear strength, it can be concluded that the optimal combination of solidified parameters is 14% of lime, 30% of fly ash, 1% of MPA, 28 days of curing time, and a dry density of 1.65 g/cm3.

This study aims to investigate the impact of three established approaches to entrepreneurship education, Theory, Competition and Incubation, on entrepreneurial entry and performance. Propensity score matching is used to compare three cohorts from the alumni of a business college in China who completed entrepreneurship courses with their respective matched sample of similar individuals who did not. The findings suggest that Incubation significantly increases the probability of new venture creation. Theory, and participation in entrepreneurial business plan Competition(s) positively affect only those students that are non-management majors. Analysis including multiple linear regression indicates that Incubation has a positive impact on new venture sales revenue, profit before tax and the number of employees. The effect of Theory and Competition on new venture performance is not significant. This study extends the current knowledge of entrepreneurship education by providing new empirical evidence for the proposition that entrepreneurship can be learned, and the relative impact of these three types of education. The findings have direct implications for policymakers, educational executives, researchers, and others interested in encouraging entrepreneurial activity.

Dust from construction field is one of sources for the atmosphere particulate pollution. In this study, a solidifying material, modified polyvinyl alcohol (MPA), is used to control the dust from soil. The controlling efficiency of the MPA is evaluated based on its anti-wind and anti-rain erosion performance under different conditions such as soil types, spraying amount of MPA, slope morphologies (gradients and unevenness), and treated time. Results indicate that the MPA can bind well with the soil particles and it is able to strengthen the integrity of the surface. Soil treated with MPA exhibits good anti-wind effects, and PM10 and PM2.5 in environment do not increase even under a nine-grade wind erosion. Soil treated with MPA can maintain the surface integrity under a rainstorm, and there are no erosion traces and mud after rain erosion. The application of MPA has no limitation in terms of soil type, soil slope, and surface morphology, and thus, it has a wide applied prospect in engineering.Implications: In order to solve the air pollution problems existing on construction sites in densely populated areas, MPA optimizes a kind of environmental agent to treat, which does not affect the later use of soil. The applicability effect was verified from the perspective of anti-wind and anti-rain erosion doubly. Research results not only can provide data support for the construction management, but also help to promote the civilization and ecological benefit of construction.

Moisture variation in porous media depends mainly on the pore characteristics. This article used the micro-computed tomography (micro-CT) (a non-destructive imaging technique to generate a three-dimensional virtual model) and the Brooks–Corey model to deduce the moisture migration in sand. Relationship between capillary rise height and time (h–t) was achieved by numerical simulation in the capillary suction process, where the parameters fractal dimension, porosity, and air–water interfacial area were obtained by the micro-CT scanning. Meanwhile, experiments of capillary rise in sand column were performed using four different sizes washed sand, and the capillary heights at different times were recorded. Results show that the capillary suction is decided by the aperture size and phase morphology simultaneously, and particle size has obvious effect on capillarity, and the wetting front lowers with the increase in grain size and the decrease in rising rate. Parameters air entry pressure and pore-size distribution index obtained by micro-CT scanning technology and empirical formula are accurate. Method of combing micro-CT images and Brooks–Corey model can predict well the capillary suction of porous media. It is also proved that the capillary suction is decided by the aperture size and phase morphology simultaneously.

大饱和度地下区域储能时,回填材料的水热运移对埋管换热器和基体间热传递的作用不容忽视.基于改进理查德方程和Marsily表观热导率,建立高含水率下回填材料(粘土、砂及砂加膨润土)的二维热湿迁移模型,并在室内搭建换热试验平台,获取3种材料的单位换热效率及排、停热工况下温、湿度场分布.结果表明:高含水率密闭系统中的Sorer效应相对较弱,可只考虑潜热的纯导热;高饱和度条件下,砂类等低持水性材料传热效果最好.但综合考虑热容能力时,在忽略热损失情况下,粘土的间歇排、取热有利于提高储能系统的有效性,经济性最高;所建数学模型与试验数据吻合度好,高温饱和条件下,水蒸气扩散及蒸发冷凝引起的水热运移可忽略,所建模型适用于大饱和度环境下回填材料的传热分析.

The artificial freezing method is commonly applied to the construction of subway cross passages and for shield receiving. The formation and characteristics of the freezing curtain are influenced by factors such as the cold source and geological conditions. The engineering properties of frozen soil and frozen structures are reflected by the distribution and evolution of the temperature. Through a low-temperature heat transfer bench, the variation characteristics of temperature and moisture fields are tested for an opening system and a closing system with a water sup-ply device, and the differences of the two fields with or without the water supply device are analyzed. The results show that the integral value along the tube length should be considered during calculation of the average temperature in the freezing region;the development process of the temperature with a water supply device is slightly faster than that without a water supply device;and the freezing front varies exponentially with time and moves faster with a water supply device.

Environmental temperature affects oil viscosity and then changes the mechanical properties of petroleum contaminated soil.Unconfined compressive strength test is carried out to study the effect of temperature on strength and deformation of saline soils in inshore contaminated by petroleum.Results indicate that:(1 )Temperature has significant effects on mechanical properties of oil contaminated saline soil.Compressive strength of petroleum contaminated soil decreases with the increasing of temperature,and reduces nearly 70%at 20°C and oil content of 1 5%comparing with that of un-contaminated soils.(2 )Unconfined compressive strength increases first and then decreases with the increase of petroleum content.There is an opposite correlation between environmental temperature and petroleum content at maximum strength.The maximum strength with oil content of 1 5%,1 0%,and 5%shows at 1 0°C,20°C and 30°C,respectively.(3)Damage of petroleum contaminated saline soils presents strain softening type with failure plane of 45°±φ/2,and it is intensified with the increasing of petroleum content and temperature.Environmental temperature has obvious effect on the deformation of oil contaminated saline soil.

经抑尘剂固化后的抗雨蚀性能是影响抑尘剂使用时效性的关键因素之一。以高分子材料——SH抑尘剂为研究对象,考虑建设场地扬尘来源（即建设场地类型土）、喷洒量、坡度、坡面形态及固化时间等因素,借助冲刷量、冲刷面破坏形态及冲刷颗粒物分布状态评价SH抑尘剂在仅固化建设场地类型土表层条件下的抗雨蚀效果。实验结果表明,SH抑尘剂可与表层土颗粒形成具有抗雨蚀能力的保护层。粉土、黏土、粉煤灰及碎石土经SH抑尘剂固化后,在暴雨强度下冲刷颗粒物少且呈散粒状,土样表面的整体完整性保持良好,无明显冲刷痕迹;SH抑尘剂对各种坡面形态及坡度均具有较好适应性,SH抑尘剂适用于场地土及裸露地表的固化;随SH抑尘剂喷量及固化时间的增加,固化土的抗雨蚀能力先增大后趋于平缓,从施工和经济角度,建议选取的SH抑尘剂喷量为1.2 kg/m~2,固化时间为3 d。

[目的]评价SH固化建设场地类型土的抑尘效果及其在建设场地中的适用性,为合理有效控制建设场地扬尘问题提供方法依据.[方法]以高分子材料-SH抑尘剂为研究对象,考虑建设场地扬尘来源(即建设场地类型土)、喷洒量、坡度、坡面形态、固化时间及堆土密度等因素,借助PM10及PM2.5指标评价SH抑尘剂在仅固化建设场地类型土表层条件下的抗风蚀性能及其在建设场地的适用性.[结果]SH抑尘剂可在土样颗粒间发挥联接作用,维持土体表面的完整性,有效解决洒水抑尘措施存在的缩裂问题;SH对于建设场地类型土(粉土、粉煤灰、黏性土、碎石土)均具有很好的抑尘效果,喷洒SH抑尘剂后,固化土在九级风力的吹蚀作用下不会造成PM10和PM2.5污染物;SH抑尘剂对于建筑堆土、建筑弃土及裸露地表均具有适用性,坡度、堆土密度、坡面形态不影响SH抑尘剂的渗透固化效果.从抑尘效果和施工经济角度考虑,建议施工时选取SH抑尘剂喷量1.2 kg/m2,固化时间3d.[结论]SH抑尘剂可在土体表层形成抗风蚀性保护膜,实现从源头控制建设场地扬尘.

Salt in saline soil has adverse effects on the stability of treated soil. In this study, the grain size, the Atterberg limits, the compaction, the strength, and the microstructure were measured successively to analyze the effects of the chlorine salt content on lime-treated saline soil. Chlorine salt had obvious effects on the structure of the lime-treated soil; it increased the quantity of coarse soil particles and decreased the total surface area of the soil. An approximately linear relationship was found between the salt content and the microstructure׳s parameters, such as the bone area, the aspect ratio, roundness, etc., while the salt content reduced the degree of homogenization of the treated soil. Additionally, the liquid limit, the plastic limit, and the plasticity index decreased with an increasing salt content. The salt content had little effect on the maximum dry density or the optimum water content, and its effect on in situ compaction was negligible. Importantly, the chlorine salt did not react with the lime, and adsorbed only onto the soil surface or into the pores. Moreover, the chlorine salt induced engineering problems in the lime-treated soil, which affected its stability, especially when the salt content was more than 3.0%. Thus, waterproofing measures should be applied to treated saline soil.

回填材料由于其工程特殊性得到广泛的应用.但作为多孔介质,其内部热传导诱发的水分运移进一步改变材料间的力学作用,产生干裂或热收缩现象.本文针对3种常用回填材料,搭建收缩试验平台,对不同时间的形变量及对应含水率进行测定,采用极差分析方法,对正交试验结果进行评价.结果表明,不同温度作用下,不同干密度回填材料的形变量差异较大.三因素影响的主次关系为:温度＞材料类型＞干密度.在地下储热系统中,需要考虑高温条件下土的失水形变特性,以有助于优化地埋管与储热体间的传热特性.

石油开采和运输过程中易于发生泄漏,造成周边土体的严重污染,优化吸附处理措施条件是需重点解决的问题.以温度、pH值、灰水比及反应时间为影响因素,通过正交试验设计方法,研究多场耦合条件下粉煤灰对石油的吸附性能.同时,借助极差分析和灰色关联度分析,确定适宜的吸附耦合条件及各因素的敏感性.试验结果表明:粉煤灰对石油具有较强的吸附性,适宜的吸附条件为灰水比为1:15 g/ml、pH值为ll、温度为35℃、反应时间为2h,石油的吸附率达到97.23％.各因素对吸附性影响的敏感程度依次为:温度＞pH值＞灰水比＞反应时间.粉煤灰对石油污染物的不可逆吸附为实现石油污染土的工程再利用了提供可能性,向石油污染土中添加粉煤灰和石灰,粉煤灰可稳定石油污染物的迁移,粉煤灰和石灰的碳化及火山灰反应可提高污染土的强度和抗变形能力.固化处理石油污染土不仅可满足工程应用的强度和变形要求,而且还可解决环境污染问题.

During freezing construction, the mechanical behavior of the frozen soil curtain mainly depends on its temperature field distribution. However, aimed at the current uniformization problems in temperature field distribution and based on the freezing construction of the No.2 cross passage of Tianjin Metro Line 2, two physical models with Midas/GTS software, i.e. one with a uniform temperature field and another with a temperature gradient, were established and a 3D numerical simulation was then carried out for the construction of a tunnel cross passage considering the nonuniformity of the cold transfer induced by concrete hydration and air heat exchange between the segment and the tunnel. The results show that stress concentration occurs at the bell mouth part of the cross passage during freezing, with a large displacement at the floor of the frozen soil curtain; the results from the model with the temperature gradient are more in line with the engineering practice regarding a more reasonable stress and deformation of the frozen soil curtain.

The energy efficiency monitoring is an essential precondition for ground source heat pump system’s controlling and energy saving operation. Based on the data monitoring applied in the school building, this work is focused on the parameters acquisition and operation analysis of the GSHP system in Tangshan. Results show the average COPs (coefficient of performance) are 2.85 and 2.70 in summer and winter, respectively, and heat(cold) unbalance underground existed after whole year operation. The analysis of data also indicates that the direct borehole air-conditioning saved some power consumption obviously in the early stage of summer and energy saving of the GSHP system depended remarkably on its operation and management level. Besides the observation points of ground temperature are laid for a large-scale GSHP system, and the hydraulic balance of the pipes group needs to be concerned specially in safeguarding better reliability.

The larger pore characteristic determines the way of the moisture transfer in sand materials.The moisture distribution and the relation between capillary rise height and time are obtained by simulating numerically the process of capillary suction in the 1D vertical sand column,where the parameters of fractal dimension and porosity are determined through the technology of Micro-CT tomography and the fitting relationship of Brooks-Corey model are gained according to the saturated hydraulic conductivity and the medium pore parameter.Meanwhile,laboratory experiment of capillary rise height is tested on 4 sizes of washed sand,and the capillary rise heights at different time are recorded.The results show that the capillary suction of sand can be simulated accurately by using parameters of scanning structure,reciprocal of air entry pressure and pore size distribution index.A predication to the migration of capillary water in sand subgrade materials can be realized.

Capillary suction is one of the vital physical parameters to porous media and has been widely concerned in engineering practice.This paper combines the Gardner soil-water characteristic curve model and the structure parameters obtained by Micro-CT tomography at first.The unsaturated capillary rise model and a specific quantification for capillary rise in the porous media are then developed using the fitting relationship between suction and saturation and the finite difference method.Furthermore,laboratory experiments are carried out to confirm the availability of the model,where the narrow sub-washed sand is chosen as object.Parameters of the capillary rise process and the stable distribution of moisture are measured actually.Results indicate that a good agreement is presented between test and theoretical values.The proposed theory is feasible to predict the capillary rise and the moisture distribution of sand.

Mine water and mine return air is good for the renewable energy due to heat storage underground, and the recycling has been a new technology of the energy utilization in water source heat pump system. Utilizing the waster heat of coal mine is beneficial in reducing the coal consumption of winter heating boiler or even replacing it completely. Comprehensive analysis the research situation and the project example, this paper points out that the technical of mine water applied for water-source heat pump system is feasibility in the practical project and theory in view of advantages, like energy saving, environmental protection, high efficiency and short payback period, etc. Therefore, application of mine water for water-source heat pump system is a new advanced energy-saving technology.