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Wanhuan Zhou - One of the best experts on this subject based on the ideXlab platform.
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estimation of maximum pullout shear stress of grouted soil nails using bayesian probabilistic approach
International Journal of Geomechanics, 2013Co-Authors: Wanhuan Zhou, Kaveng YuenAbstract:AbstractThe pullout resistance of soil nail is a key parameter in soil nailing design. Pullout resistance is affected by many factors, such as overburden Pressure, Grouting Pressure, soil dilation, and degree of saturation of soil. Because of the complexity of the pullout mechanism, some factors have not been well incorporated in the current soil nail design methods. In this study, Bayesian analysis is performed to investigate the relative importance of several key factors and to build a new design formula to estimate maximum pullout shear stress of grouted soil nails. By using a series of laboratory soil nail pullout test data, Bayesian analysis is performed to select a predictive formula with suitable complexity and to identify its parameters. It is found that the most important factors are the degree of saturation and the product of Grouting Pressure and overburden Pressure. It is shown that the proposed optimal model exhibits significantly stronger correlation with measurements than the existing effec...
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experimental study on the pullout resistance of Pressure grouted soil nails in the field
Canadian Geotechnical Journal, 2013Co-Authors: Chengyu Hong, Wanhuan ZhouAbstract:The pullout behaviour of cement-grouted soil nails, particularly in field conditions, is not yet fully understood. In this study, a series of tests was conducted to evaluate the pullout response of grouted soil nails in a field slope. A new innovative Grouting packer system was developed to control the grouted length and maintain the cement grout Pressure of the grouted part. By using the Grouting packer system, a total of 10 soil nails placed at different soil depths were grouted with different Pressures in the field. The pullout results of present field tests and a number of past laboratory tests indicate that the apparent coefficient of friction (ACF) decreases with the increase of overburden stress even though Grouting Pressure is applied. In addition, when the overburden stress is unchanged, the obtained ACF values in the field tests appear to increase almost linearly with the increase of Grouting Pressure. After the soil nails were completely pulled out of the ground, the surfaces of the soil nails ...
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simplified analytical method for calculating the maximum shear stress of nail soil interface
International Journal of Geomechanics, 2012Co-Authors: Chengyu Hong, Wanhuan ZhouAbstract:AbstractThis paper describes a simplified analytical method that considers postinstallation normal stress, normal stress due to soil dilation, and Grouting Pressure when calculating the maximum shear stress of the nail-soil interface. Systematic test results from two previous publications were used to verify the accuracy of the proposed method. The Hong Kong design method was also used to determine the maximum shear stress of the nail-soil interface. These analyses confirmed that the experimental data were more accurately predicted by the proposed analytical method. An extensive parametric study was conducted to examine the effects of several key parameters on the maximum shear stress. It was observed that when there was no Grouting Pressure, maximum shear stress increased with increasing overburden Pressure, failure surface distance, dilation angle, or decreased drill hole radius. Analysis using the proposed model also demonstrates that Grouting and overburden Pressures share an interactional effect. The...
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influence of Grouting Pressure and overburden stress on the interface resistance of a soil nail
Journal of Geotechnical and Geoenvironmental Engineering, 2009Co-Authors: Wanhuan ZhouAbstract:Grouted soil nails are widely used in slope stabilization. The influence of both Grouting Pressure and overburden stress on the soil-nail pullout interface shear resistance is still not well understood due to the complex of soil-grout interactions. A series of laboratory soil-nail pullout tests have been carried out on a completely decomposed granite soil in nearly saturated condition under a combination of different Grouting Pressures and overburden stresses. The pullout tests simulate the real construction process of a soil nail, including establishment of initial soil stresses in a soil slope, drilling a hole with stress release, Grouting, and soil-nail pullout when the slope is sliding. The pullout box is well instrumented. Test data are collected automatically by a data logger. Typical test results are presented, explained, and discussed in this paper. The soil-nail interface shear resistance data from all tests are analyzed and interpreted. The study shows that the Grouting Pressure and overburden stress have interactional influence on the soil-nail pullout resistance. Based on the test results, a new empirical liner equation with two Grouting Pressure dependent parameters is proposed for calculation of soil-nail pullout resistance considering both Grouting Pressure and overburden stress. New understandings and findings from the study are presented.
Changsheng Wu - One of the best experts on this subject based on the ideXlab platform.
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analytical method for evaluating the ground surface settlement caused by tail void Grouting Pressure in shield tunnel construction
Advances in Civil Engineering, 2018Co-Authors: Changsheng WuAbstract:The tail void Grouting is a key step in shield tunnel construction and has an important influence on the loading on the surrounding soil and on the resulting settlement. In order to estimate the ground surface settlement caused by tail void Grouting Pressure in tunnel construction, the loading on the surrounding soil is simplified as an expansion problem of the cylindrical cavity in semi-infinite elastic space. A simple analytical formula is deduced by using the virtual image technique and Fourier transform solutions. The effectiveness of the proposed method is verified by case studies. The effects of elastic modulus, tail void Grouting Pressure, tunnel radius, and tunnel depth on the ground surface heave are conducted. The results indicate that the computed results are in accordance with Ye’s solution and it is more rational to consider the ground surface heave induced by tail void Grouting Pressure in the prediction of ground settlement due to shield excavation. Moreover, the ground surface heave owing to tail void Grouting Pressure resembled a Gaussian distributed curve. Thus, no matter the ground surface subsidence or ground surface heave can be predicted by means of adding the presented empirical formula to the Peck formula which cannot predict the ground surface heave. The ground surface heave decreases with an increase in elastic modulus. On the contrary, as the tail void Grouting Pressure and tunnel radius increase, the ground surface heave increases, respectively. The ground surface heave first steadily increases and then declines gradually with the tunnel depth increase.
Daichao Sheng - One of the best experts on this subject based on the ideXlab platform.
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Performance of a compaction-grouted soil nail in laboratory tests
Acta Geotechnica, 2018Co-Authors: Xinyu Ye, Qiong Wang, Shanyong Wang, Scott W. Sloan, Daichao ShengAbstract:This study proposed a new soil nail known as the compaction-grouted soil nail, and a physical model was established to investigate its pull-out behaviour with different Grouting Pressures. The study on scale effect of the physical model was performed subsequently via numerical modelling. Additionally, interface shear tests were performed using the same boundary conditions as the physical model test. The strength parameters obtained were used to estimate the pull-out resistance of a conventional soil nail. The merits of these two soil nail types were compared based on their pull-out resistances. The physical model test results showed that the pull-out resistance of the compaction-grouted soil nail increases with increasing Grouting Pressure. In addition, the pull-out resistance exhibits hardening behaviour without a yield point, indicating that the compaction-grouted soil nail enables soils to remain stable against a relatively large deformation before ultimate failure. Furthermore, a higher Grouting Pressure results in a higher rate of increase for pull-out resistance versus pull-out displacement, which improves the performance of the compaction-grouted soil nail in the stabilization of large deformation problems. A comparison of the two types of soil nails suggests that the new compaction-grouted soil nail is more sensitive to Grouting Pressure than the conventional soil nail in terms of pull-out resistance improvement. In other words, the performance (pull-out resistance) of the compaction-grouted soil nail can be markedly improved by increasing the Grouting Pressure without inducing any accidental or undesired cracking or soil displacement.
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experimental investigation of Pressure Grouting in sand
Soils and Foundations, 2016Co-Authors: Qiong Wang, Shanyong Wang, S W Sloan, Daichao Sheng, R PakzadAbstract:Abstract Pressure Grouting technology has been widely adopted in ground improvement and soil stabilization. To better understand the grout evolution and diffusion process upon Pressure Grouting injection in sand, laboratory-scale tests were carried out on loose sand under confined boundary conditions, with different grout water/cement ( w / c ) ratios (0.5 and 1) and soil degrees of saturation (ranging from 5% to 60%) taken into account. By comparing the injected grout volume, the grout bulb volume and density, and the characteristics of the grouted bulbs (dimension and shape) obtained at increasing Grouting Pressure, the main features of the Pressure Grouting process were revealed. The injected grout volume increased almost linearly with the Grouting Pressure, and a lower volume of grout could be injected for a lower w / c ratio at the same Grouting Pressure, representing a lower injectability. An increase in the Grouting Pressure leads to an enlarged grout bulb dimension for both w / c ratios, and this increase shifts the grout diffusion process from being dominated by compaction to one involving a fracture-like pattern. Generally, a spherical grout bulb is obtained at a lower w / c ratio of 0.5; however, at the higher w / c ratio of 1, fracture starts to occur even at a low Grouting Pressure of 100 kPa and continues to propagate as the Grouting Pressure increases. The influence of the degree of saturation of the soil was significant on both the injectability and the characteristics of the grout bulbs, since the cohesion of the unsaturated sand changed along with it. When Sr exceeds 5%, the volume of the injected grout decreases, but then increases after a threshold value of approximately 40%. Conversely, compaction Grouting seems to be dominant at the threshold Sr value, while fractures tend to appear at both lower and higher degrees of saturation. A considerable amount of bleeding occurred with the two main diffusion processes during Pressure Grouting. The w / c ratio seems to be the most significant factor contributing to this behavior in sand samples.
Yang Xiuzh - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on progressive failure of subway tunnel foundation with a single cave
Journal of Railway Science and Engineering, 2013Co-Authors: Yang XiuzhAbstract:A plane strain model was designed for research according to the similarity theory,and under the consideration of the Grouting Pressure,the progressive failure characteristics of subway tunnel foundation with a single karst cave were analyzed. In the experiment,cylindrical airbag was employed to impose a load which simulates the Grouting Pressure. With the method of step-loading,the change law of the soil stress and displacement was discussed and the fracture plane was plotted. Furthermore,the ultimate failure load was derived on the basis of the similarity coefficient.
Supot Teachavorasinskun - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of liner responses due to non-uniform tail void Grouting Pressure
Geomechanics and Geoengineering, 2018Co-Authors: Supot TeachavorasinskunAbstract:ABSTRACTTail void Grouting initially does facilitate the action of ground loads around the lower half of the liner and no excess Pressure being accumulated. However, at a later stage (almost at the completion of Grouting), grout Pressure becomes non-uniformly distributed around grout injection holes especially on the upper half of the liner. In the present study, the boundary and loading conditions were simulated by using a series of finite element analyses. It aimed to explore the effects of such temporary non-uniform loading conditions on development of the liner internal forces. The results obtained for tunnel with diameter of 6.0 m were presented. It was found that there were critical locations where application of non-uniform Grouting Pressure could result in large amounts of bending moment and deformation. Those critical locations; about ±30° to ±50° from crown of the tunnel, were about the locations where actual Grouting was injected in the field. The stiffness of sub-soil beneath the tunnel invert...