An experimental study on the shear strength development of cement‐sand‐gravel (CSG) material was carried out using triaxial compression tests. The effects of the cementing agent content, aggregate content, and gradation on the shear strength of CSG material were analyzed. The shear strength remarkably increased with increasing cementing agent content and aggregate content for a given confining pressure. The increase in shear strength with increasing cementing agent content far exceeded that with increasing aggregate content. However, the stress‐strain curves and shear strength changed only slightly when the aggregate gradation for CSG material was adjusted. Based on the test data, a strength criterion for CSG material is proposed as a function of the cementing agent content, aggregate content, and shear strength of the aggregate gradation.

Considering requirements such as enhanced unit capacity, the geometric size of wind turbine blades has been increasing; this, in turn, results in a rapid increase in manufacturing costs. To this end, in this paper, we examine the aerodynamics of co-planar multi-rotor wind turbines to achieve higher unit capacity at a lower blade length. The multiple wind rotors are in the same plane with no overlaps. The ALM-LES method is used to investigate the interaction effect of the blade tip vortices, by revealing the regulation of aerodynamic performance and flow field characteristics of the multi-rotor wind turbines. The simulated results suggest an observable reduction in the blade tip vortices generated by blades located closely together, due to the breaking and absorption of the blade tip vortices by the two rotors. This results in increased aerodynamic performance and loads on the multi-rotor wind turbine. The influence between the blade tip vortex is mainly located in the range of 0.2 R from the blade tip, with this range leading to a significant increase in the lift coefficient. Thus, when the wind rotor spacing is 0.2 R, the interaction between the blade tip vortices is low.

Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect of cement content on the deformation properties of CSG material, we employ triaxial compressive tests for cement contents of 20, 40, 60, 80, and 100 kg/m³ with a confining pressure range of 0.3–1.2 MPa, and theoretically analyze the results by the regression analysis prediction method. Here, we show that both cement content and confining pressure influence the deformation properties of CSG material: for an increase in cement content, the failure strain decreases and brittleness of CSG material increases; the initial modulus of the CSG material increased exponentially with increasing cement content or confining pressure; the peak volumetric strain and its corresponding axial strain increase linearly with increasing confining pressures, which decrease with increasing cement content; the initial tangent volumetric ratio can also be determined by the peak volumetric strain and its corresponding axial strain.

As an environmentally friendly, green, and low-carbon construction material, cemented sand and gravel (CSG) dam is widely used in civil engineering and water conservation projects in China. This study describes the progress of research on CSG dams (materials) in recent years, including the progress of engineering related to cemented gravel dams, the static, dynamic, and thermodynamic properties and intrinsic structure models of dam building materials, the static, dynamic, and temperature field analysis of dam structures, and the design of dam profiles; and on this basis, it proposes the direction of further research and development of cemented gravel structures, which will provide research for new cemented gravel structures in China. Structure design, old and diseased engineering structure removal and reinforcement, and safety assessment to provide research status and new ideas.

In this paper, the effects of different influencing factors and factor interaction on the compressive strength and permeability of recycled aggregate pervious concrete (RAPC) were studied based on the response surface method (RSM). By selecting the maximum aggregate size, water cement ratio and target porosity as design variables, combined with laboratory tests and numerical analysis, the influences of three factors on the compressive strength and permeability coefficient of RAPC were revealed. The regression equation of compressive strength and permeability coefficient of recycled aggregate pervious concrete were established based on RSM, and the response surface model was optimized to determine the optimal ratio of RAPC under the conditions of meeting the mechanical and permeability properties. The results show that the mismatch item of the model is not significant, the model is credible, and the accuracy and reliability of the test are high, but the degree of uncorrelation between the test data and the model is not obvious. The sensitivity of the three factors to the compressive strength is water cement ratio > maximum coarse aggregate particle size > target porosity, and the sensitivity to the permeability coefficient is target porosity > maximum coarse aggregate particle size > water cement ratio. The absolute errors of the model prediction results and the model optimization results are 1.28 MPa and 0.19 mm/s, and the relative errors are 5.06% and 4.19%, respectively. With high accuracy, RSM can match the measured results of compressive strength and permeability coefficient of RAPC.

With the great impetus of energy conservation and emission reduction policies in various countries, the proposal of concepts such as “Sponge City” and “Eco-City”, and the emphasis on restoration and governance of ecological environment day by day, portland cement porous concrete (PCPC), as a novel building material, has attracted more and more attention from scientific researchers and engineers. PCPC possesses the peculiar pore structure, which owns numerous functions like river embankment protection, vegetation greening as well as air-cleaning, and has been of wide application in different engineering fields. This paper reviews the salient properties of PCPC, detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years (2010–2020), conducts the statistical analysis of the distribution rule of its major properties around the world, combines with the engineering application to summarize the excellent properties of PCPC, and makes a forecast of future research direction.