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The distribution and magnitude of the shear stress at the interface between the grout of a compression anchor rod and rock are strongly affected by the Poisson effect. A new analytical equation of the influence coefficient of the Poisson effect is proposed to quantitatively evaluate the influence of the Poisson effect on the interfacial shear stress. When the Poisson effect is considered, the interfacial shear stress from the neutral point to the bearing plate increases, and the distribution curve becomes steep. However, the interfacial shear stress far from the neutral point is low, and the distribution curve becomes smooth. Overall, the Poisson effect leads to a more nonuniform distribution of the shear stress at the interface of the compression anchor rod. A larger Poisson's ratio, smaller elastic modulus, and smaller diameter of the grout lead to a greater influence of the Poisson effect. Furthermore, a larger elastic modulus of rock leads to a greater influence of the Poisson effect. The Poisson's ratio of rock and that of grout both affect the Poisson effect greatly, but the influence of the variation in the Poisson’s ratio of rock on the Poisson effect is negligible. A larger interface friction angle leads to a greater influence of the Poisson effect.

The pile-soil stress ratio (PSSR) is the key to the design and construction of geosynthetic-reinforced pile-supported (GRPS) embankments. However, the computation models for the PSSR which takes account of the effect of consolidation settlement of soil among piles (SAP) is not complete. This paper splits the piles and the SAP into multiple small elements for iterative calculation, according to the principle of the collaborative actions between pile, soil, embankment and reinforcement. The calculation method for pile-soil interaction was improved by Davis’ 1D nonlinear consolidation theory, and the hyperbolic load transfer model of pile-soil interface proposed by Wong and Teh. Then, a novel computation model for the PSSR of GRPS embankments was established, under the joint impact of soil arching effect, tension membrane effect and improved pile-soil interaction. Finally, this proposed computation model was proved reasonable by the comparison with tests and other methods, and the effects of key parameters were investigated. The results show that the settlement difference between piles and SAP increased with the degree of consolidation of the SAP and the elapse of time; the PSSR below the reinforcement net (RN) is slightly higher than that above the RN; the PSSRs above and below the RN are both positively correlated with the degree of consolidation and initial bulk compressibility of the SAP.

The mechanical and cracking behaviors of rock mass are strongly affected by natural discontinuities and confining pressure. Uniaxial and triaxial compressive experiments were conducted on intact and single- and double-flawed granite specimens using MTS 815 electrohydraulic servo-controlled triaxial testing system to understand further the influences of confining pressure and fracture on rock strength and failure mode. Confining pressures of 5 MPa and 10 MPa were designed in this study. The effects of the confining pressure and the configuration of pre-existing flaws on the mechanical and cracking behaviors of flawed granite specimens were studied numerically using PFC. Experimental study results show that under the same confining pressure, the stress–strain curve of the intact granite specimen drops rapidly at the peak stress point, whereas the deformation with different numbers of flawed granite shows a stepwise softening phenomenon, which occurs when the confining pressure is relatively small. However, such phenomenon becomes progressively unobservable as the confining pressure increases. With the increase in confining pressure, the mechanical property of the granite gradually turns from brittle to ductile. Consequently, the cracking behaviors become progressive. Numerical simulation results show that the tensile fracture of flawed granite specimens is often observed under a low confining pressure, whereas the tensile–shear mixture fracture and the shear fracture of flawed granite specimens are often observed under moderate and high confining pressures, respectively. Under a constant confining pressure, the peak stress of flawed specimens decreases with the increase in the number of prefabricated flaws and the stress concentration becomes more serious, thereby decreasing the number and development degree of the micro-cracks outside the stress concentration region of the specimens.

In order to study the change law of volume deformation and particle breakage of calcareous sand under cyclic loading, this paper carries out both conventional triaxial consolidated drained shear tests (the conventional tests) and triaxial cyclic loading tests on calcareous sand. The test results under these two stress paths were compared and showed that, compared with the stress path of the conventional tests, the stress path of cyclic loading aggravates the softening features of the calcareous sand. In each cycle, there is a hysteresis loop in the stress-strain curve, whose area is proportional to the deviator stress level at the initial stage of unloading. The stress path of cyclic loading suppresses the dilation trend of the sample under low cell pressure; the contraction amount is positively correlated with the deviator stress in the unloading phase. The two stress paths bring similar particle breaking law. Under the same cell pressure, the shear moduli of calcareous sand particles decrease with the growing cycle number. The manuscript clarified the law of deformation and particle breakage of calcareous sand under cyclic loading, which provided a theoretical basis for practical engineering.

The floor heave and the inward movement of sidewalls are often encountered in the excavation of tunnels with swelling rock properties. However, the deformation mechanism for swelling soft-r...

Lateral displacement of pile foundation is crucial to the safety of an overall structure. In this study, a numerical simulation on the lateral displacement of pile foundation under stacking loads was conducted to determine its relation with different influencing factors. Simulation results demonstrated that stacking loads at the pile side mostly influence the lateral displacement of pile foundation. The lateral displacement of pile foundation increases by one order of magnitude when the stacking loads increase from 100 kPa to 300 kPa. Other influencing factors are less important than stacking loads. Lateral displacements of the pile body and at the pile top can be reduced effectively by increasing the deformation modulus of surface soil mass, reducing the thickness of soft soil, and expanding pile diameter. Our analysis indicates that a nonlinear relationship exists between the lateral displacement at the pile top and the pile diameter. The lateral resistance of the pile body can be enhanced by coupling the stacking load along piles and the axial force at the pile top. An actual large-scale engineering project was chosen to simulate the effects of postconstructed embankment on lateral displacement and axial force of bridge pile foundation under different construction conditions and to obtain the lateral displacement of the pile body and the negative frictional resistance caused by soft soil compression under stacking loads. On the basis of the calculated results, engineering safety and stability were evaluated, and a guide for the design and construction was proposed.

Cracks are a type of damage often present in earthen sites, which have a particular influence on the structural performance. Cracks constitute preferential paths for rainfall infiltration, directly moistening the rammed earth and substantially reducing its mechanical properties. Therefore, the repair of cracks is an important part of the protection and reinforcement of earthen sites. Calcium carbonate is one of the main components of the tabia. The use of microbially induced carbonate precipitation (MICP) to repair and protect the tabia is not only environmentally friendly but also compatible with the substrate. In this paper, a crack-repair method dominated by MICP is proposed to repair the cracks of the tabia, and the repair effect is evaluated by experimental methods. First, the influencing factor test of MICP and the reinforced soil column test were carried out to determine the suitable parameters for repairing cracks, including the concentrations of bacteria and cementation reagent, filled soil particles and the number of grouting cycles. Then, the pre-damaged tabia samples were repaired using the suitable parameters, and the repair effect was verified. The results showed that when the crack width is 5 mm, the average flexural strength and shear strength recovery ratios of the specimens after MICP repair were 79.92% and 88.54%, respectively, showing a very satisfactory repairing ability. However, the recovery ratio tends to decrease as the crack width increases. In addition, the static contact angle test results showed that the MICP not only repaired the crack but also enhanced the hydrophobicity of the crack. MICP technology can be used as an effective method to repair cracks in the tabia.

Rain erosion is one of the most important factors causing the weathering of ancient clay roof tiles. Weathering damage generally proceeds from the surface to the interior; thus, protecting tile surfaces is an effective method to resist weathering. In this study, the microbially induced carbonate precipitation (MICP) technique is used to form an anti-erosion layer on the surfaces of tiles. Next, the applicability of MICP for tile surface erosion control is examined in the laboratory by the static contact angle test, capillary water absorption test, Karsten tube test, durability test, acid resistance test, water vapour permeability (WVP) test and colour change test. Moreover, the effect of the concentration of bacteria and cementation reagent on the surface erosion control is analysed. The test results show that MICP can significantly improve the water resistance of tiles by changing the microstructure of the surface. Higher concentrations of bacteria and cementation reagent allow the sediment layer to provide better protection; however, this effect is not linear. The concentration threshold reduces the positive effect of the bacterial concentration on the water resistance of the sample surface. The MICP protection layer offers favourable durability with little negative impact on the air permeability and colour of the sample. The use of an MICP protection layer can effectively relieve the weathering of ancient clay roof tiles.

Low-grade concrete-cored sand-gravel (CCSG) pile composite foundation is a new kind of composite foundation for thick and soft clay ground treatment. An analytical solution was derived for calculating the consolidation process of this composite foundation by considering coefficients of horizontal permeability in smear zone, the radial flow within the sand-gravel shell, and the impervious property of concrete-cored pile. The results show that Terzaghi’s one-dimensional consolidation solution and the consolidation analytical solution of ordinary composite foundation were special cases of this solution. Curves of the average consolidation degree of the composite foundation under various nondimensional parameters were observed using the program based on the theoretical formula. Meanwhile, a series of in situ measurements including the settlement of pile and soil, the pore water pressure, and the total stress under embankment load were obtained on the CCSG pile composite foundation on a section of Zhenjiang-Liyang highway. The analyzed results show that the new style composite foundation patent technology has many advantages such as small differential postconstruction settlement (differential is not good, small is), reliable quality, high bearing capacity, and stability. And the consolidation of composite foundation is largely affected by the nondimensional parameters. The analytical solution is finally verified with the actual measurement data.