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Permeation grouting is widely used in grouting engineering because of its low grouting pressure and minor disturbance to the stratum. However, influenced by the complex properties of sand layer and slurry, an accurate prediction of the groutability of the sand layer remains to be a hard work. In this paper, the permeability of sand layer is studied based on a self-designed permeation grouting test device, which considers the different sand particle size, relative density of sand layer, slurry water-cement ratio, and clay content. The influencing factors of sand layer groutability are analyzed, and the different parameters that affect the grouting of sand layer are evaluated, thus proposing a new approach to predict the groutability of sand layer. Results show that the sand particle size and slurry water-cement ratio are positively related to the groutability of sand layer, and the relative density and clay content of sand layer are negatively correlated with the groutability of sand layer. The proposed alternative empirical formula to estimate the groutability of sand layer will help predict the groutability of sand layer with a higher degree of accuracy, which can provide a certain reference for engineering.

Hydrogen bonding and mechanical refining are closely correlated. In this work, structural variations of hydrogen bonding patterns in cellulose during mechanical pulp refining, including the hydrogen bonding energy and distance as well as the content of hydrogen bonds, have been explored by using the second derivative FTIR spectra and deconvolving spectra in the OH stretching vibrational region. Results show that except for the bond distance, both the hydrogen bonding energy and the content of hydrogen bonds exhibit a significant variation at an increasing beating degree. The calculated hydrogen bonding energies for intermolecular O6H⋯O3' decrease by 12.9%, while those of intramolecular O3H⋯O5 and O2H⋯O6 vary little. Evolutions of the content of certain hydrogen bonds differ depending on the different refining stage. It is suggested that along with the role of water, hydration and swelling, internal/external fibrillation and delamination are strongly related to the structural variations of hydrogen bonding patterns in cellulose during mechanical pulp refining.

Grouting is generally applied as an effective way to seal rock fractures, reduce permeability, decrease deformation, increase strength of rocks, and to stop the water flow through the jointed rock mass. But grouting rock fractures under condition of flowing water depends greatly on experiences of professional engineers, without sufficient theoretical guidance to refer to, as no commonly accepted and reasonable theoretical models are available. To describe the grouting process of fractures in flowing water, and put forward reasonable grouting guidance suggestions. The present work established a theoretical model for grouting into a fracture with flowing water. Considering boundary conditions, a streamline equation of grouting diffusion trajectory with flowing water was derived, and analyzed the influence of boundary effect on grouting diffusion law. The simulation tests of grouting rock fracture with flowing water were carried out on the self-developed fracture grouting experimental platform, and the results were compared with the theoretical prediction results, which verified the rationality of the theoretical model. The results show that there are three types of diffusion of quick-setting slurry under condition of flowing water. The existence of boundaries can increase the penetration along the direction of the flowing water both downstream and upstream, but it weakens the penetrability in the vertical flow direction. Rock fractures with a high water velocity require a high grouting flow rate, however, it is not the higher the better for determining the relevant grouting flow rate, a decrescent ratio between these two parameters should be ensured as a precondition.

Stable passive mode-locking multi-segment composite Nd:GdVO 4 lasers with a semiconductor saturable absorber mirror were demonstrated for the first time. For the composite crystals, the output power increased linearly with the increase of the incident pump power, showing excellent thermo-mechanical performances. While for the conventional crystal, power saturation was observed when the incident pump power exceeded 8.79 W. The maximum average output power of 1.465 W was achieved by Nd(0.1%):GdVO 4 /Nd(0.5%):GdVO 4 /Nd(1%):GdVO 4 composite crystal at an incident pump power of 9.28 W. The largest pulse energy of 14.90 nJ and the highest peak power of 0.53 kW with a pulse duration of 28.0 ps were also obtained by using the same composite crystal, revealing that the multi-segment composite crystal with a proper combination of Nd 3+ -doped concentrations could obtain the optimal laser performance.

The number of tunnel lining leaks is currently increasing during construction and operation. Through the comprehensive analysis of the system, the fundamental method for solving the leakage problem of the lining is explored. Through the repeated occurrence of seepage water leakage in the lining of Jinggangshan Station of Qingdao Metro, a set of system leakage water treatment methods was proposed, from pre-grout preparation, general cement slurry treatment, superfine cement slurry focus, chemical slurry replenishment. The lining aesthetics restores the five processes for treatment, and the five steps are integrated to achieve the effect of radical cure. And through field practice to verify, the method is highly feasible and the governance effect is good. It has strong applicability to the leakage of underground engineering lining, and can better solve the difficult problem of the lining leakage water that is currently faced.