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Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the development of soil cracking. With the rise in carbon fiber content to 0.2%, 0.4% and 0.6%, the crack rate of soil cracking decreased by 7.9%, 17.3% and 23.3%, respectively, while the fractal dimension of soil cracking decreased by 2.4%, 8.7% and 21.2%, respectively. Accordingly, the critical moisture content of the soil samples increased by 33.2%, 110% and 151%, and the time of the soil constant evaporation stage decreased by 5.1%, 13.8% and 34.5%, respectively. When carbon fiber is combined with soil, carbon fiber will increase the interface bonding strength, friction and interlocking force, effectively inhibiting the cracking of soil, and it provides a channel for water transport in the soil in the early stage. [ABSTRACT FROM AUTHOR]

The paper proposes the scheme of split-level which is for the problems of downslide of roadway and flying refuse and slice slope in pseudo-inclined working face of thick seam with large dip angle in Suhanghe Coal Mine. The instability mechanism of supports is analyzed by establishing a mechanical model of its stability, and it shows that the slope section plays a key control role in controlling the equipment sliding. It can effectively reduce the sliding trend of the supports and improve the stability of the supports. Through numerical simulation, the law of strata pressure in working face is analyzed. The stress release zone and tensile failure zone of working face roof are asymmetrically distributed, and the tensile failure zone corresponds to the collapse line. Based on the field measurement, the adaptability of the support is analyzed. The support can meet the demand of safe production. The strength of the working face is not symmetrical. The rock pressure in the middle of the working face is the strongest, the dynamic load coefficient is 1.66, followed by the upper part, and the lower part is relatively flat.

To explore the relationship between permeability characteristics of rock mass and stress field and temperature field, the mechanical behavior law of rock mass under coupling conditions is further obtained. Under the coupling conditions of temperature field, seepage field and stress field, the numerical simulation of triaxial compression tests of rock mass with different confining pressure gradients and Darcy permeability coefficients is carried out. This paper shows that the confining pressure chamber is one of the factors that influence the permeability of rock mass. Under the same conditions of other fields, the larger the confining pressure, the lower the permeability of rock mass. The stress field acting on the rock mass has obvious influence on the seepage field flowing through the rock mass. The influence of seepage field through rock mass on temperature field inside rock mass is dominant. The effect of stress field acting on rock mass on the temperature field of rock mass distribution is not very significant. The triaxial compression test simulation of rock mass under multi-field coupling condition shows that the end effect is remarkable, the stress distribution at the edge is concentrated, and the stress distribution of rock mass is symmetrical.

Soil drying cracking is the most common natural phenomenon affecting soil stability. Due to the complexity of the geometric shapes of soil cracks during the cracking process, it has become a major problem in engineering science. The extremely irregular and complex crack networks formed in civil engineering materials can be quantitatively investigated using fractal theory. In this paper, fractal dimension is proposed to characterize the drying cracking characteristics of composite soil by adding recycled waste brick micro-powder. At the same time, the concept of the probability entropy of cracking is introduced to quantify the ordered state of crack development. Correspondingly, the endpoint value of probability entropy was solved mathematically, and the meaning of the probability entropy of cracking was clarified. In this study, the fracture fractal characteristics of composite soil mixed with different materials were first investigated. Then, five groups of composite soil-saturated muds with added recycled waste brick micro-powder of different contents were prepared in the laboratory. Using the evaporation test under constant temperature and humidity, the change rules of the fractal dimensions, probability entropy, crack ratios, and water contents of cracks during the cracking process of the soil samples were obtained. The results show that: (1) on the whole, the fractal dimensions of the soil samples added with recycled waste brick micro-powder of different contents increased over time, and the fractal dimensions of the soil samples without recycled waste brick micro-powder were obviously larger than those of the soil samples with recycled waste brick micro-powder. With the increase in the content of recycled waste brick micro-powder, the maximum fractal dimension decreased in turn. The maximum fractal dimensions of the five groups of soil samples were 1.74, 1.68, 1.62, 1.57, and 1.45. (2) The change trends of the probability entropy and fractal dimensions were similar; both of them showed an upward trend over time, and the probability entropy of the soil samples without recycled waste brick micro-powder was greater than that of the soil samples with recycled waste brick micro-powder. With the increase in the contents of recycled waste brick micro-powder, the probability entropy decreased in turn. The maximum values of the crack probability entropy of the five groups of soil samples were 0.99, 0.92, 0.87, 0.83, and 0.80. (3) Under the action of continuous evaporation, the moisture contents of the soil samples gradually decreased over time, while the crack ratios increased over time. To sum up, both from the perspective of the development process of the cracks of the soil samples and from the perspective of the final stable crack networks of the soil samples, the geometric shapes of the cracks of the soil samples without recycled waste brick micro-powder were the most complex. With the increase in the content of recycled waste brick micro-powder, the fractal characteristics of the cracks gradually changed from complex to simple. [ABSTRACT FROM AUTHOR]

Soil surfaces form complex crack networks as a result of water loss and shrinkage. A crack network destroys the integrity of the soil and becomes the main factor affecting rainfall infiltration, slope instability and soil integrity. In this paper, a soil fracture network is quantified using fractal characteristics and fractal dimensions, and the soil fracture network is identified and calculated using digital image processing technology. The fracture network of silty clay with different setaria viridis root content is studied during the process of evaporation. Saturated mud is prepared by taking soil samples and collecting setaria viridis roots. The content of setaria viridis roots in each saturated mud sample is 0 g, 0.1 g, 0.2 g and 0.3 g. In the artificial climate environment simulation system, thin-layer root soil is dried by controlling the temperature and humidity to simulate dry climate conditions. During the test, the crack development process is recorded using a digital camera. The results show that when the root content is 0, 0.1 g, 0.2 g and 0.3 g, the water content values when a fissure is generated are 35.2%, 41.2%, 42% and 46.4%, and the initial fractal dimension values are 1.100, 1.106, 1.112 and 1.115, respectively. The fractal dimension value increases rapidly in the early stage of fissure generation, and it reaches the maximum value when the water content reaches 13.66%, 15.2%, 15.66% and 17.98%, respectively. According to the change law of the fractal dimension, the fractal dimension increases rapidly following the initial appearance of the fracture, and, with a continuous reduction in water content in the later stage, the fracture characteristics gradually stabilize, and the change rate of the fractal dimension becomes slow. [ABSTRACT FROM AUTHOR]

Clostridium tyrobutyricum is suitable for simultaneous saccharification and fermentation of lignocellulosic. It can produce butyric acid, acetic acid as its main fermentation products from a wide variety of carbohydrates such as glucose, xylose, cellobiose and arabinose. In order to decrease acetic acid content and increase butyric acid content in C. tyrobutyricum, we replaced genes on the acetic acid fermentation pathway with genes on the butyric acid fermentation pathway. Three genes were selected. They were acetyl-CoA acetylrtansfers gene (thl) which is the key enzyme gene associated with acetic acid fermentation pathway from Clostridium acetobutylicum, erythromycin gene (em) from plasmid pIMP1 and phosphotransacetylase gene (pta) which is the key enzyme gene associated with butyric acid fermentation pathway from C. tyrobutyricum. We fused these genes with pUC19 to construct nonreplicative integrated plasmids pUC19-EPT. Then we transformed pUC19-EPT into C. tyrobutyricum through electroporation. The recombinant transformants grown on plates containing erythromycin were validated by PCR. A mutant whose pta gene was displaced by thl gene on the chromosome was selected. In the fermentation from glucose, the mutant's yield of butyric acid is 0.47, increased by 34% compared with wild type; and the yield of acetic acid is 0.05, decreased by 29% compared with wild type.