Deformation mechanism of roadways in deep soft rock at Hegang Xing’an Coal Mine

Engineering geomechanics characteristics of roadways in deep soft rock at Hegang Xing'an Coal Mine were studied and the nature of clay minerals of roadway surrounding rock was analyzed. This paper is to solve the technical problems of high stress and the difficulty in supporting the coal mine, and provide a rule for the support design. Results show that mechanical deformation mechanisms of deep soft rock roadway at Xing'an Coal Mine is of ⅠABⅡABCⅢABCD type, consisting of molecular water absorption (the ⅠAB -type), the tectonic stress type + gravity deformation type + hydraulic type (the ⅡABC -type), and the ⅢABCD -type with fault, weak intercalation and bedding formation. According to the compound mechanical deformation mechanisms, the corresponding mechanical control measures and conversion technologies were proposed, and these technologies have been successfully applied in roadway supporting practice in deep soft rock at Xing'an Coal Mine with good effect. Xing'an Coal Mine has the deepest burial depth in China, with its overburden ranging from Mesozoic Jurassic coal-forming to now. The results of the research can be used as guidance in the design of roadway support in soft rock.

The principle of stability control of surrounding rock-bearing structures in high stress soft rock roadways

Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was put forward.The supporting principlesof high stress engineering soft rock roadway (high resistance and yielding support,timelysupport,high strength and high stiffness supports) were proposed,which were applied inengineering practices,and obtained better achievements.

NORMALIZED RELATION OF CYCLIC DEGRADATION BEHAVIOUR ON SOFT CLAYS

The effect of the consolidation stress σc and the consolidation ratio kc on the cyclic degradation relation is studied by cyclic triaxial tests of soft clay. The results show that the normalized relation among the cyclic modulus, the damping ratio, the accumulative deviatoric strain and the cyclic degradation parameter can be established if the cyclic stress ratio and initial shear stress ratio are used as normalized parameters. Thereby the reasonable method is supplied to measure and apply cyclic parameters of soft clay.

Floor heave in the west wing track haulage roadway of the Tingnan Coal Mine: Mechanism and control

Floor heave of a roadway is a dynamic phenomenon that often happens in the roadways of coal mines. It seriously affects safe production in the coal mine. Floor heave has long been one of the most difficult problems to be resolved during coal mining. An analysis of floor heave in the soft rock surrounding the roadway, and the factors influencing it, allowed the deformation mechanism in the west wing double track haulage roadway of the Tingnan Coal Mine to be deduced. Three types of floor heave are observed there: intumescent floor heave, extrusion and mobility floor heave, and compound floor heave. Control measures are proposed that have been adopted during a recent repair engineering project. Control of the floor heave in the west wing track haulage roadway was demonstrated. The reliability and rationality of a combined support technology including floor anchors, an inverted arch, and anchoring of both sides was verified by mine pressure data and the field observations. Waterproofing measures were also under-taken to assist in the control of floor heave.

Alginate nanobeads interspersed fibrin network as in situ forming hydrogel for soft tissue engineering

Hydrogels are a class of materials that has the property of injectability and in situ gel formation.This property of hydrogels is manipulated in this study to develop a biomimetic bioresorbable injectable system of alginate nanobeads interspersed in fibrin network.Alginate nanobeads developed by calcium cross-linking yielded a size of 200e500 nm.The alginate nanobeads fibrin hydrogel was formed using dual syringe apparatus.Characterization of the in situ injectable hydrogel was done by SEM,FTIR and Rheometer.The developed hydrogel showed mechanical strength of 19 kPa which provides the suitable compliance for soft tissue engineering.Cytocompatibility studies using human umbilical cord blood derived mesenchymal stem cells showed good attachment,proliferation and infiltration within the hydrogel similar to fibrin gel.The developed in situ forming hydrogel could be a suitable delivery carrier of stem cells for soft tissue regeneration.

Synthesis of biodegradable waterborne phosphatidylcholine polyurethanes for soft tissue engineering applications

To further improve the biocompatibility of polyurethanes,a new lysine 2-(2-aminoethoxy)ethanol phosphatidylcholine(LAPC)is synthesized to use as chain extender for preparing a series of phosphatidylcholine polyurethanes(PCPUs).Poly(e-caprolactone)(PCL)and poly(ethylene glycol)(PEG)are used as soft segments,and L-lysine ethyl ester diisocyanate(LDI),LAPC and L-lysine are used as hard segments.The obtained PCPUs exhibit appropriate mechanical properties with break elongation of 1000–1700%,tensile strength of 7–22 MPa,and relatively high elastic modulus of 11–18 MPa,which could admirably satisfy the requirement for soft tissue engineering scaffolds.The phosphatidylcholine structures can increase the hydrophilicity of PCPU surfaces,which effectively reduce protein adsorption and platelet adhesion while promoting the cell proliferation.In addition,the LAPC chain extender,PCPU films and ultimate degradation products of PCPUs are proved to be nontoxic in cytotoxicity test.More interestingly,the cytokine release test of macrophages manifests that both LAPC and PCPU degradation products could effectively improve the proliferation of macrophages and induce them into a wound-healing phenotype.Thus,the obtained PCPUs have greatly potential applications of soft tissue engineering scaffolds for tissue repair and wound healing.

Adipose tissue derived stromal cells in a gelatin-based 3D matrix with exclusive ascorbic acid signalling emerged as a novel neural tissue engineering construct:an innovative prototype for soft tissue

The current study investigated a triad,which comprises of adipose tissue derived stem cells isolated from infrapatellar fat pad and gelatin/polyvinyl alcohol(PVA)-based matrix with exclusive ascorbic acid signalling.Though,the bio-mechanical properties of the gelatin–PVA blended scaffolds in wet condition are equivalent to the ECM of soft tissues in general,in this study,the triad was tested as a model for neural tissue engineering.Apart from being cytocompatible and biocompatible,the porosity of the scaffold has been designed in such a manner that it facilitates the cell signalling and enables the exchange of nutrients and gases.The highly proliferative stem cells from Passage 2 were characterized using both,mesenchymal and embryonic stem cell markers.As an initial exploration the mesenchymal stem cells at Passage 4 were exposed to ascorbic acid and basic fibroblast growth factor signalling for neuronal differentiation in 2D environment independently.The MSCs successfully differentiated and acquired neuron specific markers related to cytoskeleton and synapses.Subsequently,three phases of experiments have been conducted on the 3D gelatin/PVA matrix to prove their efficacy,the growth of stem cells,growth of differentiated neurons and the in situ growth and differentiation of MSCs.The scaffold was conducive and directed MSCs to neuronal lineage under specific signalling.Overall,this organotypic model triad could open a new avenue in the field of soft tissue engineering as a simple and effective tissue construct.

Utilizing 3D bioprinted platelet-rich fibrin-based materials to promote the regeneration of oral soft tissue

Oral soft tissue defects remain difficult to treat owing to the limited efficacy of available treatment materials.Although the injectable platelet-rich fibrin(i-PRF)is a safe,autologous source of high levels of growth factors that is often employed to promote the regeneration of oral soft tissue,its effectiveness is restrained by difficulties in intraoperative shaping together with the burst-like release of growth factors.We herein sought to develop a bioactive bioink composed of i-PRF,alginate and gelatin capable of promoting the regeneration of the oral soft tissue.This bioink was successfully applied in 3D bioprinting and exhibited its ability to be shaped to individual patient needs.Importantly,we were also able to significantly prolong the duration of multiple growth factors release as compared to that observed for i-PRF.The growth factor bioavailability was further confirmed by the enhanced proliferation and viability of printed gingival fibroblasts.When deployed in vivo in nude mice,this bioink was further confirmed to be biocompatible and to drive enhanced angiogenic activity.Together,these data thus confirmthe successful production of an i-PRF-containing bioink,which is suitable for the individualized promotion of the regeneration of oral soft tissue.