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This paper takes No. 52 return uphill roadway of Yangquhe coal mine as a research project. Based on the research, especially its geological condition, indoor experiments, numerical simulation and theoretical analysis were employed to determine the difficult coefficients of Yangquhe project. By using these means, the difficult coefficients of the deep rock engineering were determined. From a study of the effects of crustal stress and the roof mechanism on roadway stability, the transformation mechanism in Yangquhe coal mine has been determined. As a result of this research, the interactive support technology of pre-stressed cable mesh was developed and the technology tested in mining engineering, which proved to be feasible. Keywords: Deep mining, Return airway, Destruction mechanism, High strength, Complementary support

The drawdown velocity of foundation pit water level in existing projects is mostly determined empirically, and the influence of water level drawdown velocity on the seepage field and stress field in the weir body is not fully considered. The water level change of the foundation pit is an important factor affecting the stability of the cofferdam. Therefore, it is of great practical significance to study the variation law of seepage field and stress-strain field of cofferdam during the pumping process of foundation pit, to accurately judge the stability of cofferdam slope and to formulate reasonable pumping and drainage scheme. Based on the 1th temporary earth-rock cofferdam of Yongning Water Conservancy Project, the nonlinear finite element method is used to calculate the spatial-temporal evolution of seepage field and stress-strain field of earth-rock cofferdam under different drawdown velocity of water level. The overall deformation of the cofferdam, the shear failure and instability characteristics of the slope, and the influence of water level changes on the stability of the cofferdam slope are analysed. The results show that the distribution of unsaturated zone and negative pore pressure zone is basically the same. The excessive water level drawdown velocity is easy to break the balance between the seepage field and the water level fall time, resulting in the rise of saturation line height and the increase of the upper bending rate. The effect of seepage control is weakened, and the stability of the slope is poor. The shear deformation of the cofferdam slope develops from the foot of the slope and extends to the crest of the cofferdam until it runs through. At the same time, local plastic deformation occurs at the foot of the outer stone slag berm, and the maximum deformation transits to the foot of the inner slope. Under the action of seepage force, the stability of the inner slope is always smaller than that of the outer one; the change of water level drawdown velocity is very sensitive to the stability of the slope, when the drawdown velocity is greater than the critical velocity, the stability of the slope decreases sharply. Combined with the characteristics of earth-rock cofferdam, on the basis of satisfying the stability of cofferdam, the drawdown velocity of water level should be controlled within 1.28m/d. The research results of the thesis have reference significance for the selection of pumping speed of foundation pit similar to earth-rock cofferdam.

In recent years, steel sheet pile cofferdam has been adopted in some hydropower reconstruction and extension projects because of its many advantages. However, due to insufficient understanding of the bearing mechanism of super-high cellular cofferdam and lack of Engineering experience, there is no exact method to accurately predict the deformation and failure forms of the cofferdam, and there is no perfect safety and economic design theory, which restricts its popularization and application. Taking the Tarbela 4th Extension Project as background, the mechanical behavior and stability evaluation of the cofferdam in 30m deep water during construction and operation are studied by FEM, and influence of structural form and parameters on deformation characteristics of key parts is analysed. Results show that the maximum interlock tension occurs near mudline or top of berm during high lateral load. Development distribution of shear deformation are more in line with the Kitajima Shoichi’ method. The overturning deformation of cell can be effectively restrained by embedment, the rotation point changes regularly with the increase of berm and embedment. The sliding surface in cell conforms to Hansen’s calculation theory, the position of rotation and change of base pressure are closer to the Japanese standard. With the stiffness loss, the change of interlock tension is similar to the damage of low carbon steel, the shear sliding surface is related to berm which above the top overturning deformation is the largest. Based on the stability of cofferdam, there are various combinations of berm height and embedded depth, which can reduce the quantity of embankment works and the cost of later maintenance. The research results are of reference significance for the design and construction of similar super-high steel sheet pile cofferdams.

A novel series of poly(2-chloroethyl glycidyl ether)-based side-chain liquid-crystalline copolymers has been synthesized in which the mesogenic units are biphenyl 4-methoxybiphenyl, 4-methoxyazobenzene, and N-benzylidene-4-methoxyaniline, respectively (corresponding polymers are referred to as PCBH, PCMB, PCMA, and PCBM). The structures of the compounds obtained are characterized by infrared (IR) and 1H nuclear magnetic resonance (NMR). The thermal properties were investigated using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction analysis. The results indicate that PCMA, PCMB, and PCBM exhibit thermotropic liquid-crystalline behavior and present nematic phases with Schlieren textures. However, PCBH does not display a mesogenic phase. The decomposition temperatures of copolymers begin at 290°C.

Three novel copolymers, poly[1-(4-(benzothiazole-2-thio-alkyloxy)-biphenyl-4′-oxy)2.3-epoxypropane]s, were synthesized by the reaction of polyepichlorohydrin with obtained monomers, 4-(benzothiazole-2-thio-alkyloxy)biphenyl-4′-ols, in which the number of methylene unit in substitution group of biphenyl group was 2, 4, 6, respectively. The structures of obtained compounds were confirmed by elemental analysis and 1H NMR. The decomposition temperatures of copolymers were near 340 °C. Differential scanning calorimetry (DSC) measurement and polarized optical microscopy (POM) observation showed the resulting copolymers did not exhibit thermotropic liquid crystalline mesomophism and belonged to semi-crystalline substance.

BACKGROUND: Owing to the unusual structural rearrangement of polychloromethylthiirane (PCMT) at room temperature, it has not been used as the main-chain backbone of side-chain liquid-crystalline polymers (SLCPs). However, it has been observed that PCMT has a relatively stable and clear structure under special conditions. Therefore, we attempted to synthesize SLCPs using PCMT as main-chain backbone and investigated their thermal behavior. RESULTS: New polymers, poly[1-({(4-methoxyazobenzene-4′-oxy)alkyl}thio)-2,3-epithiopropane], in which the number of methylene units in the alkyl group is 4, 5 or 6, were prepared by means of reactions of corresponding (4-methoxyazobenzene-4′-oxy)alkylthiols with PCMT. The structures of these compounds were confirmed using elemental analysis and 1H NMR spectroscopy. The substitution ratios of the copolymers with 4, 5 and 6 methylene units in the alkyl group were 56, 75 and 80%, respectively. Differential scanning calorimetry measurements and polarized optical microscopy observations showed that the resulting copolymers exhibited thermotropic liquid-crystalline mesomorphism with nematic phase except for the copolymer with a 56% substitution ratio. The decomposition temperature of all the synthesized copolymers was near 195 °C. CONCLUSION: This investigation has demonstrated that PCMT polymerized for 8 h has the ability to act as a suitable main-chain backbone for SLCPs. Moreover, SLCPs could be obtained only by the reaction of PCMT with thiolate salt containing mesogenic groups. The substitution ratios increased with increasing number of methylene groups in the spacer. Copyright © 2009 Society of Chemical Industry

A series of side-chain liquid-crystalline polymers, poly[N-(4-methoxyazobenzene- 4′-oxyalkyl)ethyleneimine](PEnZO), has been synthesised in which the number of methylene units in spacers varies from two to six. The structures of the synthesised monomers and polymers were confirmed by infrared (IR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. The thermal properties of these polymers have been investigated using differential scanning calorimetry (DSC), polarising optical macroscopic (POM) X-ray diffraction and thermogravimetric analysis (TGA). The test results indicated that the obtained polymers exhibited thermotropic liquid-crystalline mesomorphism of nematic type with schlieren textures. It was observed that the thermal behaviours of the polymers were strongly dependent on the degree of substitution and the length of spacers. Polymers containing less than 57% of mesogenic groups did not exhibit mesogenic phase and resembled amorphous polymer. A more pronounced odd–even effect in the melting p...

A novel series of side‐chain liquid crystalline copolymers, i.e. poly‐[1‐({(4‐methoxyazobenzene‐4′‐oxy)alkyl}thio)‐2.3‐epoxypropane]s, were synthesised in which the number of methylene units in the alkyl group of the side chain varies from 3 to 6. The structures of compounds obtained were characterised by elemental analysis and 1H NMR spectroscopy. Thermal properties were investigated using polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction analysis. The synthesised thiols and corresponding polyepichlorohydrin‐based copolymers exhibited thermotropic liquid crystalline behaviour and nematic phases with schlieren textures. The thiols have lower transition temperatures than the corresponding copolymers. In addition, the degree of substitution of the copolymers synthesised increased with an increase in number of methylenes in the side chain. The phase transition temperatures increased and the mesomorphic temperature ranges widened with the increasing degree of substitution ...

A series of polyether chelating resins with pendent biphenyl mesogenic groups were synthesized, and the chemical structure of monomers and polymers were confirmed by IR and 1H NMR detection. The thermal properties of resins were investigated by the Differential Scanning Calorimetry (DSC) and Polarizing Microscopy (POM), and the results showed that only the product of polyepichlorohydrin grafted with 4-cyano-4’-hydrobiphenyl, i.e., HPCN resin, was a kind of nematic liquid crystal polymer with typical schlieren texture (70-130 0C) and other resins were semi-crystalline. The results of adsorption experiments showed that all five resins exhibited a higher adsorption capacity (>1.0 mmol/g) for Cu (II) and Hg (II) and medium adsorption ability for Cd (II), Zn (II), Pb (II) and Co (II), however, a poor adsorption capacity (