Hongtao Wang

The interaction between slurry and concrete cracks influences the grouting diffusion process during the grouting repair engineering of cracked concrete material. Compared to a single-cracked concrete material, the slurry–concrete crack interaction mechanism of a multi-cracked concrete material is more complicated. This study employs the Monte Carlo method to generate a crack group with a certain probability distribution for characterizing the random cracks in the concrete material. The cracked concrete material is simplified as a pore–crack medium model, and the continuity equation of the slurry in the model is derived. Furthermore, based on the modified interface layer theory, the coupling effect of the slurry–concrete crack is elucidated, and the variation law of each crack opening in the concrete material under different grouting pressures is examined. When the slurry diffuses in a multi-cracked concrete material, the crack opening changes mainly stem from the crack distribution position and crack tendency. Under the same grouting pressure, four main forms of changes occur in the crack opening: gradual increase along the crack distribution, slow decrease, first increasing and then decreasing, and, basically, unchanged. When the grouting pressure increases, crack groups with the same distribution form have similar crack opening change rules, but the change range varies. Under the same grouting pressure, as the number of cracks in the concrete material increases, the coupling effect of the concrete material becomes increasingly obvious.

In this research, the compressive behavior of closed-cell aluminum foam was examined across a broad strain rate spectrum, spanning from 0.005 s⁻¹ to 2000 s⁻¹. Utilizing an enhanced Hopkinson bar apparatus, the deformation and fracture mechanisms of the foam were captured through high-speed videography. Additionally, a microscale finite element model was developed to elucidate the dynamic deformation characteristics of aluminum foam at multiple scales. The findings indicate that the material’s response is highly strain rate-dependent, with both stress levels and energy absorption efficiency escalating as the strain rate rises. Moreover, the damage progression in aluminum foam manifests as a progressive collapse pattern.

As a typical pullout foundation, the uplift pile has been widely used in ocean projects or geotechnical engineering, but the accurate prediction of its ultimate pullout capacity has always been a difficulty in engineering design. This study focused on a single pile in rock formation, and constructed a curved uplift failure mechanism in the case that the whole rock mass around the pile was damaged. In this mechanism, the rock mass failure was assumed to comply with the Hoek–Brown failure criterion. Then, the theoretical prediction formulas for the rock failure surface and the ultimate pullout capacity of the pile were derived by using the upper bound theorem. The influence laws of factors such as different rock mass parameters, pile parameters and additional surface load on the pile capacity and failure range were analyzed. Further, the proposed method was validated by comparing with the numerical simulation results. The results show that the ultimate pullout capacity of the pile increases with the increase in the length/diameter ratio, rock empirical parameter A, tensile strength, compressive strength, unit weight and additional surface load, but decreases with the increase in rock empirical parameter B. Empirical parameters A and B are key factors affecting the pile capacity and rock failure range, and should be attached importance to in engineering design. The research work in this study can provide some theoretical reference for the design of the uplift pile in rock formation.

In this paper, taking a typical roadway in broken and soft rock strata in No.10 Mine of Pingdingshan coal field as an example, the deformation and failure mechanism of rock mass was deeply analyzed based on field testing. Then the technology of high-strength prestressed bolt-grouting support, such as the new combined high-strength grouting bolt, high-strength hollow grouting anchor cable, were developed. Based on this, a repair support scheme using the new technology was designed for on-site roadway, and was successfully implemented in the field. The monitoring results after the repair of field roadway show that the maximum of roadway surface convergence deformation is 56mm. The maximum force of the grouting bolt is 122kN, the grouting anchor cable is 256kN. The new technology can fill the cracks of rock mass and the borehole interstice at the free part by using grouting materials. It can effectively enhance the self-bearing performance of soft broken rock mass on the premise of ensuring the diffusion of prestressed active supporting effect in rock mass, and then suppress the deformation and failure of roadway. The research works can provide references for the stable control and support design for roadways in soft and broken rock strata.

Affected by confined aquifer, basal inrush accidents caused by excavation are common in foundation pits, and accurate estimation of the safety thickness of the base is a big concern of engineers. In this paper, a three‐dimensional failure mechanism of base inrush was constructed for a rectangular foundation pit. In this mechanism, the strength of the soil mass was assumed to be nonhomogeneous along the depth, and the soil‐mass failure satisfied the linear and nonlinear Mohr–Coulomb strength criteria. Then, based on the limit equilibrium theory, the prediction method for the safety thickness of the base against confined water inrush was deduced, and a comparison with existing research works was conducted. Furthermore, the influence laws of soil strength parameters, pit design parameters, and confined water pressure on the critical safety thickness were analyzed. The results show that the critical safety thickness of the base is positively correlated with nonlinear coefficient and confined water pressure but negatively correlated with cohesion, internal friction angle, nonhomogeneity coefficient, and unit weight. The soil strength is a key factor affecting the base safety thickness, which should be paid enough attention to in engineering design and construction. The research findings in this paper can provide a theoretical reference for the prevention and control of basal inrush accidents in confined water strata.

Determination of the required supporting pressure is the premise of tunnel support design. Only when the support design meets the requirements can the tunnel be safe and stable during construction and operation. This paper focuses on a shallow tunnel in layered rock strata and proposes a method for predicting the required supporting pressure. In this method, the 2D and 3D failure mechanisms are constructed, respectively. The analytical solutions of the supporting pressure corresponding to the two cases are derived on the basis of upper bound theorem and Hoek–Brown failure criterion. Then, the proposed method is validated by comparing with the results of existing research studies. Furthermore, a shallow tunnel in two‐layer rock strata is chosen to illustrate the difference between the two solutions. The comparison shows that the supporting pressure in the 2D case is greater than that in the 3D case in general and it tends to be conservative for tunnel design. Conversely, the 3D solution may help to reduce the support cost. Furthermore, the change laws of the supporting pressure and failure range corresponding to varying parameters are obtained. These results may practically provide theoretical references for tunnel support design in layered rock strata.

Layered rock strata are observed to be common during the excavation of tunnels or cavities, and may significantly affect the deformation and failure characteristics of surrounding rock masses due to various complex forms and mechanical properties. In this paper, we propose a three-dimensional axisymmetric velocity field for roof collapse of shallow cavities in multi rock layers, by considering the influences of roof cross-section shapes, supporting pressure, ground overload, etc. The internal energy dissipation rate and work rates of external forces corresponding to the velocity field are computed by employing the Hoek-Brown strength criterion and its associated flow rule. Further, the equations of the collapse surfaces and the corresponding weight of collapsing rock masses are derived on the basis of upper bound theorem. Furthermore, we validate the proposed method by comparing the results of numerical calculations and existing research findings. The change laws of the collapse range under varying parameters are obtained for the presence of rectangular and spherical cavities. We also find that the three-dimensional mechanism is relatively safer for engineering designing actually, compared with the traditional two-dimensional mechanism. All these conclusions may provide workable guidelines for the support design of shallow cavities in layered rock strata practically.

In this study, we propose a method for predicting the supporting pressure required for shallow tunnels in layered soils, based on a curved roof collapse mechanism with multi-failure surfaces. In this method, the effect of the number and thickness of soil layers, pore water pressure, arbitrary roof profile, and ground additional load is considered simultaneously. A nonlinear power-law failure criterion is employed to describe the failure characteristics of the roof soils. The internal energy dissipation rate and the work rates produced by external forces are obtained based on the associated flow rule and plasticity potential theory. The analytical expressions of the required supporting pressure and roof collapse surfaces are obtained with the upper bound method. Furtherly, a shallow rectangular tunnel in two soil layers is selected for parametric investigation. The change laws of the required supporting pressure and collapse curves under varying parameters are obtained. Furthermore, the corresponding engineering recommendations are given, which may potentially provide references for the support design and construction of shallow tunnels in layered strata.