Experimental Research On the Performance of a Novel Geo-Filament Anchor For An Earthen Architectural Site

An efficient anchoring method, explicitly developed for small sliders, has hitherto been missing in the practice of earthen architecture conservation. Furthermore, anchoring performance studies conducted so far, have failed to fully take into account the soil characteristics of certain targets. To address these concerns, the conservation project conceived for the Gaochang Ruins, Turpan, in China, was selected as the testing ground to design a novel Geotechnical Filament Anchor (GFA) for reinforcing small sliders in the earthen historical ramparts. In-situ experiments were conducted for evaluating six parameters—anchoring length (L), GF thickness (H), bore diameter (D), grouting strength (S), GFA surface status (R), and inclination angle (A). These parameters were varied in order to determine the effect they produce on anchoring performance, as demonstrated by the indicators, including tensile strength, destruction mode, load displacement (P-S) relation, and strain (ζ-L) distribution characteristics of the novel GFA. Data acquired from the experiments, in combination with the conservation specifics of earthen architectural sites, anchoring performance, and safety reserve, were further employed to introduce a calculation formula for computing the designed force value (N) through L. A simplified model depicting the shear stress distribution of the anchoring system under N was devised by extracting the strain distribution data with respect to the GF-grouting interface. Taking into account the soil properties of the above-mentioned site, the shear stress diffusion coefficient (α) was conceptualized, the formula for the shear strength of the grouting material was devised, and the tolerable ranges of L, D, H, R, and S were determined. Thus, a feasible anchoring method for small sliders used in earthen architectural sites is proposed, and validated by strong and reliable experimental and theoretical groundwork.

Dehydration-induced mechanical instabilities in active elastic spherical shells

Active elastic instabilities are common phenomena in the natural world, where they have the character of sudden mechanical morphings. Frequently, the driving force of the instability mechanisms has a chemo-mechanical nature, which makes the instabilities very different from the standard elastic instabilities. In this paper, we describe and study the active elastic instability occurring in a swollen spherical closed shell, confining a water-filled cavity, during a dehydration process. We set up a few numerical experiments based on a stress-diffusion model to give an insight into the phenomenon. Then, we present a study that looks at the chemo-mechanical problem and, through a few simplifying assumptions, allows us to derive a semi-analytical model of the phenomenon. It takes into account both the stress state and the water concentration in the walls of the shell at the onset of the instability. Moreover, it considers the invariance of the cavity volume at the onset of instability, which is due to the impossibility of instantaneously changing the cavity volume filled with water. Eventually, it is shown that the semi-analytic model matches very well the outcomes of the numerical experiments far from the initial regime; the ranges of validity of the approximated analytical model are also discussed.

Failure Analysis of Deep Composite Roof Roadway and Support Optimization of Anchor Cable Parameters

The stability of the roadway surrounding rock is the key factor of underground mining. Roof subsidence occurred during roadway excavation in the Menkeqing Coal Mine. For the sake of safety, it was decided to stop tunneling project and strengthen roadway support, which resulted in a delay of the construction period and economic damage. To maintain the stability of the surrounding rock, we carried out a systematic study through field monitoring, theoretical analysis, and numerical simulation. The deformation and failure law of the surrounding rock, roof structure characteristics, and mechanical properties of the surrounding rock were obtained by field monitoring. The failure characteristics and forms of deep composite roof roadway are further analyzed. The key points of stability of the roadway surrounding rock of soft rock composite laminated roof are obtained by theoretical analysis, i.e., improving the effective stress diffusion efficiency of the anchor cable through the reasonable arrangement of the anchor cable. We use FLAC numerical simulation software to study the influence of different supporting parameters of anchor cable on the stress diffusion in the surrounding rock and put forward the optimal parameters. The optimized support parameters have been applied in the field, and the ideal results have been obtained.