Rectangular barrettes are increasingly being used to support large-size and heavy-duty structures, but the interaction among barrettes, soil, and cap has rarely been studied theoretically. This paper presents an approximate three-dimensional semi-analytical method for the analysis of load–displacement behaviour of single barrettes, barrette groups, and barrette–soil–cap interaction systems. A unique feature of a barrette, which distinguishes it from a circular pile, is its nonaxisymmetrical mechanical behaviour. To take into account this feature, both the barrette–soil and the cap–soil interfaces are discretized. Mindlin's solution is adopted to define the load–displacement relationship of the soils next to the barrette and the cap. By assuming the deformation compatibility at the barrette–soil and cap–soil interfaces, the load–displacement relationship of the soils is incorporated into the static force equilibrium conditions in the interior of the barrette and cap structures. In this way, governing equations in finite difference form are derived for obtaining the load–displacement response of the barrette–soil–cap system. The proposed method is verified by comparing the calculated results for a group of square piles using other existing methods. In addition, some factors such as barrette shape, barrette spacing, and barrette group layout and finite-layer depth, which influence the response of the barrette–soil–cap system, are investigated.Key words: elasticity, foundations, numerical modelling, piles, theoretical analysis.

Based on the paste-like roadway backfill technology in the study of coal mining under the freeway in Tang’an Mine, the mining scheme of coal under the freeway is described. In order to grasp the change law of the stress and damage degree of coal pillars and surrounding rocks during the coal mining process of roadway backfill, analyze the stability of coal pillars and the amount of roof subsidence, using FLAC3D numerical simulation method, select the width of coal pillar elastic plastic zone, the vertical stress of the column and the vertical displacement of the roof are used as indicators. The influence of the 15m temporary coal pillar width on the stability of the coal pillar, the stress distribution of the surrounding rock and the sinking of the roof under the mining method are studied to verify the feasibility of the mining scheme.

No abstract

In the background of big data, the innovation process of new material enterprises is the result of full and effective integration of many external forces. This paper analyzes the impact and challenges of the emerging big data phenomenon on new material enterprise innovation, including internet plus, material genome project and so on. This paper also puts forward the mechanism of external driving force for innovation of new material enterprises in the big data environment, and discusses the influence of DMAIC model on the decision-making of new material enterprises. Finally, the paper expounds how to establish a multivariate and opening innovation platform for new material enterprises based on big data ecosystem under the two major support systems of internet of things and cloud computing, so as to make full use of various big data resources to serve the innovation and development of new material enterprises.

Rock-like materials can be used as a filling material to improve the stability of underground engineering substantially. And the optimization of the rock-like material is an effective way to improve the performance of the filling material. Firstly, the AHP-FUZZY comprehensive optimization model was constructed for the complexity and fuzziness of the rock-like filling material ratio optimization. Secondly, according to the mechanical properties of rock-like filling materials under special environment (such as high temperature, high humidity, high stress, and high airtight) in old goaf, mechanical properties of rock-like filling materials were studied with the method of field core and laboratory test, which revealed the variation law of mechanical properties with time, and the regression equation between mechanical parameters and time was established with the method of least squares. Finally, the strength and deformation characteristics of rock-like filling materials were monitored by the monitoring and early warning technology. The results show that the optimal ratio of the rock-like filling materials is “E3”; that is, the cement content is 9%, the ash ratio is 2 : 5, and the mass concentration is 74%. The mass concentration is the main factor that affects the slump of the slurry, and the proportion of fly ash and coal gangue content directly affects the stratification and bleeding rate of the slurry. Reasonably increasing the ash and gangue ratio can significantly improve the workability and water retention of the rock-like filling materials. Also, the amount of composite cementitious material is the main factor that affects the setting time and the strength of the rock-like material. What is more, the special environment in gob is good for each chemical reaction fully in rock-like filling materials and strengthens the gelling property of deformation resisting capability, which can be a benefit for disaster prevention of underground engineering.