Shanghai Urban Construction Municipal Engineering Group Co.

Shanghai, China

Shanghai Urban Construction Municipal Engineering Group Co.

Shanghai, China

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Wang H.,Shanghai Urban Construction Municipal Engineering Group Co. | Wang H.,Hong Kong Polytechnic University | Zhou S.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

As the present main design method of excavation engineering, the bar-load-spring model, naturally induces several problems which need to be solved. A unified calculation method of the pressure on the supporting structure considering the soil-water interaction is presented, which is more reasonable in the load calculation. Since safety factors system based on the bar-load-spring theory may not be enough to incorporate all the failure modes of foundation pits, new safety factors controlling stability of foundation pits and existing safety factor modified to reflect the size effect should be recommended. Current excavation design method took the influence of safety factor on deformation into account, which was different from the idea of traditional safety factors. Two bar system FEMs such as the bar-load-spring model of circular pits and double stiffness model of soil spring at the passive zone are proposed, which can consider size effect of circular pits and space effect of soil excavation divided into block in strip foundation. Some future research directions on excavation are pointed out.


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2016

In dealing with geotechnical engineering problems with the traditional soil mechanics, the elastic mechanics approach is often used to calculate the stress distribution in soil. The calculation of the stresses in soil is usually based on simple Boussinesq's solutions which are derived on the assumption that the loading acts on the ground surface. However, building foundations are generally buried in a certain depth beneath ground surface. In this case, the Mindlin solution is more suitable to calculate the stress distribution. The equations for calculating stresses in a semi-infinite elastic solid subjecting to a vertical rectangular and strip uniform load are significant for many geotechnical problems, such as the calculation of foundation settlement and the analysis of the influence of excavation size on its stability and deformation. Although all the equations have been presented in Reference [1-2] by Yuan Ju-yun, several errors are found in these equations. Based on the Mindlin's formulas, the calculation equations for calculating stress in the soil subjecting to a vertical rectangular uniform load beneath the surface are derived by the integral method again. Furthermore, the equations for strip load in similar case are deduced, both of which are different from those given in Reference [1-2]. Eventually, the correctness of two groups of formulations is verified by the numerical integration. © 2016, Academia Sinica. All right reserved.


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

There is a large error in calculating foundation settlement of small size by using the layerwise summation method based on consolidation tests, while the calculation of foundation settlement based on the plate load tests can not reflect the deformation characteristics of the foundations of large size. Considering the theoretical and experimental basis in calculating the foundations settlement under large-area loads by means of the layerwise summation method based on the e-p compression curve, which can be deemed as the upper limit of the practical foundation settlement with the same base pressure, while p-s settlement curve can reflect the deformation characteristics of the foundations of small size, which can be deemed as the lower limit of the practical foundation settlement with the same base pressure. Based on the above theory, an interpolation algorithm for the foundation settlement is proposed, and the issues of determining the modulus of compressibility are transformed into those of finding the interpolation functions. This algorithm can reduce the absolute error produced by the traditional algorithm to the relative error within a certain range so as to improve the calculation accuracy of foundation settlement. Furthermore, a method to predict the foundation settlement is suggested by adopting two load test results under different load plate sizes, whose rationality is verified through four-group plate load tests on the same foundation. And the interpolation function of a circle foundation is derived and analyzed to show the process of foundation settlement calculation through the interpolation method. The analysis results show that the foundation settlement curves gradually change from concave to convex when increasing the size of foundations. The proposed method combines the results of the consolidation tests and plate load tests, which can reflect the settlement characteristics of the foundations of different sizes. It is suitable for promotion in engineering practices with its clear theoretical and experimental basis and simple and convenient calculation process.


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

Common shapes of excavations include strip, rectangle, circle and pistol. When other conditions are the same, excavations with different shapes have different safety coefficients of heave-resistant stability. However, all recommended methods from existing guidelines for heave-resistant stability analysis ignore the influence of excavation shape on the safety coefficient. In this paper, based on an unloading model of excavation, a new safety coefficient has been defined which takes into account the plane shape, dimensions and embedment ratio. The safety coefficients for various excavation shapes, such as strip, rectangular and pistol, can be calculated analytically based on the definition. For circular excavations, the coefficient can be calculated by numerical integration, so the challenging problem of analyzing the stability of circular excavations is solved. When the diameter of circular excavations is large enough, the safety coefficient will be identical to that of extra wide strip excavations, indicating the wide applicability of the proposed safety coefficient. For excavations with a small embedment ratio of retaining wall in clay stratum, the proposed safety coefficient converges to the result from the Terzaghi method. The variation of the bearing capacity coefficient of foundation soil calculated using the proposed method is consistent with that of recommended values, and its rationality can be validated by field data and results from the strength reduction method. Field statistics indicate that there is a definite relationship between the safety coefficient and the deformation of circular excavations and the relationship can be used to determine the acceptable safety coefficient of excavations. © 2015, Science Press. All right reserved.


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

The separate and combined calculation of water-soil pressures on underground structures affects not only the design of supporting structures of excavations, but also the setting of uplift piles. Based on the field data, it has been proved to be reasonable to calculate the water-soil pressures by the separate calculation method for sandy soil. However, whether the combined calculations of the water-soil pressures is scientific or not for clay has been the focus dispute between geotechnical engineering and academic circles. In order to resolve this dispute, the author has proposed a calculation method to unify the separate and combined calculations of water-soil pressures. As a logically self-consistent theory, it carries out the transition between the two conventional calculation methods and provides a theoretical basis for the combined calculation method of water-soil pressures. This paper reviews the process of this theory initiation and further illustrates its rationality. Finally, it analyzed the value and development prospects of this theory. ©, 2015, Academia Sinica. All right reserved.


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2016

In order to consider the effect of shape and depth of foundations in estimation of bearing capacity of foundation soils and stability analysis of excavations, an approximate analytical method to calculate the bearing capacity factor Nc is proposed. According to this method, the estimation of bearing capacity of foundations with different shapes and depths can be unified into the same equation. If the depth of the plastic zone is properly modified, the calculated results will be very close to those from the laboratory test data and the field investigations. It was proven by this method that the value of Nc in the calculation of bearing capacity is identical to that in the analysis of excavation stability. On the basis of the method, the influence of embedment depth of the enclosure structure can be taken into account in the Terzaghi's method for analysis of the stability against heave of excavations. Moreover, an approximate approach to estimate the bearing capacity factors of shallow foundations is also put forward. © 2016, Chinese Society of Civil Engineering. All right reserved.


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

For resolving controversy of separate and combined calculation of water and earth pressures and theoretically proving that combined calculation of water and earth pressure is reasonable under some circumstances, it is necessary to establish a unified algorithm that is able to integrate separate and combined calculations in a theoretical framework. This paper establishes a unified calculation theory of water and earth pressures through the ideal model test and verifies its scientificity at the same time. Based on the ideal model test, a new strength theory is proposed that can be applied to the unified algorithm. From the calculation example we can see slight differences between the results of new and traditional methods. This new unified algorithm can be used to calculate water and earth pressures separately for sand and change to combined calculation for clay. Moreover, this can also be applied to calculate the water and earth pressures for aquitard strata like clayey silt and silty clay. It provides a theoretical basis for the calculation of load on underground structures.


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co. | Zhou S.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

The shear force in retaining structure of foundation pits will be too large while the lowest support is set too high, which may lead to punching shear failure of the retaining structure. Such failure is a kind of brittle fracture and it usually occurs suddenly, which may result in disastrous consequences. The safety factor commonly used can only control the embedment depth of retaining structures, but they can not control the height of the lowest support. So, such failure can not be avoided. Therefore, the safety factor of the punching shear-resistant stability is proposed. The failure modes and features of punching shear failure of the retaining structure have been described. And then, the calculation method of the safety factor of the punching shear-resistant stability is put forward. The study results show that even all other safety factors are satisfied, it is still necessary to check the safety factor of the punching shear-resistant stability and to analyze the rationality of the lowest support height. The safety factor of the punching shear-resistant stability is applied to explain the failure mechanism of collapse accident of a domestic metro foundation pit. Calculation analysis also shows that using the safety factor to control the height of the lowest support can achieve a linear relationship between various safety factors and embedment ratio. The safety factor is simple in form and easy to calculate;so it has important applications to design and construction of the foundation pits.


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Engineering practices and model test results all indicate that overburden soil stratum is often able to withstand greater head pressure than the pressure of its own weight. Currently, no relevant theory can explain this phenomenon. The concepts such as generalized buoyancy, generalized buoyant unit weight and generalized hydraulic gradient are proposed by considering adsorptivity of soil particles to pore water as well as considering connectivity of bound water; and then specific calculation method is given, explaining the physical meaning of the parameters such as ξs, ξv and ξ used in the calculation and recommending the estimating method of ξv. The tests envisaged on measuring ξs and ξv are also given, then the relationship between ξs and initial hydraulic gradient ib is established. Aforesaid calculation method takes the different natures of soil into account. For sand and loose soil, generalized buoyancy, generalized buoyant unit weight and generalized hydraulic gradient are changed into Archimedes buoyancy, traditional buoyant unit weight and hydraulic gradient. Further, calculation method of seepage force in different soils has been given. In the end, the unified expression of failure conditions of soil under the action of groundwater is got, which can interpret several different failure modes of soil under the action of groundwater. According to this theory, the calculating method of anti-seepage stability and the stability of resistance to the confined water of foundation pits should be amended and the current calculation method can only be applied to sand and loose soil. Some conclusions derived by using this calculation method to analyze the stability of soil in groundwater under different strata combinations are different from traditional arguments. For example, when analyzing the embedment depth of enclosure structures, if there is no impact of confined water, the seepage failure of the foundation pit is difficult to occur in the clay stratum and the ability of foundation pits to resist seepage failure in the silt stratum is better than that in sand layer. When analyzing the anti-upbursting of confined water in foundation pit, the traditional ballast-balance calculation is unsafe to the overburden soil stratum with permeability, while for the overburden soil stratum of confined water stratum containing a certain amount of silt, its ability to resist the confined water pressure is relatively increased. Finally, based on the result of the paper, the unified calculation theory on soil-water pressure is amended.


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2014

The plane shape, size of the excavation and embedment depth of the retaining wall all affect the heave-resistant stability of excavations. However, the influence of above factors can't be comprehensively expressed by the calculation methods of safety coefficient of heave-resistant stability recommended from existing standards and codes. In order to solve this problem and differentiate the situations, the possible failure modes of basal heave are classified; and thereby the corresponding formulas calculating the safety coefficient of heave-resistant stability under different failure modes are given. Based on this method, the heave-resistant stability of excavations will be influenced by the strength, stiffness and embedment depth of the retaining wall. The calculation analyses indicate that, for both the drained and undrained situation, the narrow excavations are more stable than wide ones, and that the stability can be improved by adjusting the embedment depth of the retaining wall. The improved excavation safety factor, can take more factors into account, which provides a theoretical method to reduce the embedded depths of the retaining wall of narrow excavations. ©, 2014, Academia Sinica. All right reserved.

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