共查询到20条相似文献，搜索用时 31 毫秒
1.
When shield crossed the sandy cobble stratum in Chengdu metro line 1, ground subsidence reached as high as dozens of times. The losing stability of excavation face caused excessive ground loss. Conditions of engineering geology and hydrogeology about sandy cobble stratum in Chengdu were analyzed. Mechanical characteristics of sandy cobble were obtained via large-scale triaxial test. According to the low cohesion and heavily discrete characteristics of sandy cobble, numerical computation was conducted by discrete element method. Based on numerical simulation of the large scale triaxial test, the micro parameters of the sandy cobble were calibrated. The influence of support pressure on shield excavation face deformation, surface settlement, max horizontal displacement and stress of soil was analyzed. The results show that: 1) Collapse pattern of excavation face by numerical simulation coincides with result of centrifuge model test in sand. 2) When supporting pressure is small, contact forces of particle in front of excavation face is low. The tendency of particle flow is apparent. Since over-excavation is easily brought out, cavity in the ground is caused after shield tunneling. 3)Soil arching effect in shield construction is obvious. Shield excavation forms cavity in deep ground and obvious earth surface collapse is not observed. This is main reason for lagged settlement phenomena of shield tunneling in Chengdu. 相似文献
2.
Compared with conventional tunneling methods, ground movements behave some different patterns, such as surface heave induced by tail grouting. Through the analysis of ground surface heave due to tail grouting in three cases, the applicability of Gaussian equation and six analytic methods (including Mindlin's problem, Sagaseta method, Verruijt-Booker method, Loganathan-Poulos method, Chi method and Park method) to predict ground surface heave induced by tail grouting were verified. Based on case studies, one modified Peck equation was proposed to calculate ground surface movements, including grouting heave due to shield tunneling. The results show that the Gaussian equation and Chi method are applicable to calculate surface heave due to shield tail grouting, and the Modified Peck Equation can predict the total transversal ground surface movements rationally. 相似文献
3.
Based on complex variable theory in plane elasticity, the equivalent spring stiffness is derived from the analytical solution by means of simplifying shallow shield tunneling to semi-infinite plane with hole, which is applied to response displacement method. The performances of the analytical solution are evaluated and compared with that of the deep shield tunneling through a series of selected various tunnel depths and soil Poisson's ratios. The relation of compression and shear spring stiffness is discussed. Meanwhile, two factors affected soil spring stiffness, tunnel depth and soil Poisson's ratio, are also analyzed. It is shown that soil spring stiffness of shallow shield tunneling is different from that of deep shield tunneling, and the ratio of compression and shear spring stiffness varies along shallow shield tunneling. It is also found that the value and distribution law of soil spring stiffness of shallow shield tunneling greatly depend on tunnel depth and soil Poisson's ratio. 相似文献
4.
CHEN Shu shen 《保鲜与加工》2001,(4):123-126
This paper draws up a formula to estimate the pressure to drive static pressure piles penetrating the cobble stratum. The related engineering material is analyzed to verify the correctness of the formula. Some conditions needed to estimate the pressure are put forward. 相似文献
5.
Mechanical behavior of Suspen domes during construction is different with that in service and even more adverse because of cables introduced in the structures. By studying the actual suspen dome projects, the key construction parameters for them were extracted and tensioning mechanism of hoop cables was studied. Then according to the tensioning mechanism and the key construction parameters, a numerical model and an algorithm for the whole process of tensioning were proposed. Moreover, a case study was addressed to approve the effectiveness. 相似文献
6.
In order to study the stability of foam in place cavity wall, the capacity of reinforced concrete strip ear and tie involving in cavity wall deformation, the broken shapes and mechanical performance of the cavity wall, the effective measures was seaked to improve deformation capacity and overall performance of the cavity wall.13 patches of cavity wall and 1 patch of solid wall were built and seismic tests of which were carried out.The lnfluence of some constructional measures on mechanical behavior and deformation properties of the wall and vertical pressure and insulation layer thickness on the relative displacement difference of the internal and external wall of foam in place cavity wall was analyzed.Finally, the capability of reinforced concrete strip ear and tie working interactively between the internal and external wall of foam in place cavity wall was analyzed.It is found that deformation capacity of the cavity wall is improved efficiently with constructional column and the high bonding strength, shearing strength and pressure strength of foam in place insulating mortar have certainly a positive influence on the bearing capacity of the wall.The reinforced concrete strip ears play the leading role in reinforcing connection of the internal and external wall of foam in place cavity wall and guaranteeing out plane stability of the external wall.When walls crack seriously, the ties can play an important role in supporting and drawing the wall and preventing wall collapse.Furthermore, the reinforced concrete strip ears and ties which are the main construction measures to coordinate the internal and external wall work together perform a great variety of tasks.Therefore, the reinforced concrete strip ears and ties should be designed rationally to guarantee playing their respective roles. 相似文献
7.
In process of the tunnel construction throw New Austrian Tunnelling Method, the result of smoothwall blasting to rock tunnel is not good, there are more and more cavities produced behind the lining. On the basis of engineering project, this paper makes the three-dimensional elastic-plastic analysis throw numerical simulation, discusses the stress-strain behavior of primary support when there is a different size of rectangle cavity behind the lining. In addition the safety factor of tunnel is calculated with cavity based on the strength reduction finit element method. This factor is compared with the factor of health tunnel. The stability of tunnel structure system is estimated through the linear regression analysis between stress of lining and safety factor. 相似文献
8.
According to the complex conditions of deep excavation in Nantong mine, FLAC program are carried out for strata movement, ground pressure and surface displacement due to coal extraction. Based on the analysis of Nantong mine, the basic features of strata movement, the fundamental behavior of ground pressure and the related parameters of surface displacement are obtained. The results are of referential value for mining, supporting and preventing of surface displacement. 相似文献
9.
Integrated with the study on Chengdu space developing strategy, in this paper, the problem about Chengdu water resource is analyzed and it is concluded that the Chengdu water resource has comparative advantage and can support its great development.But the construction mode must be observed.On the microscopic layer, the water resource was deteriorated in Chengdu City.A fundamental of gradual eco-construction is suggested, which is adapted to the city space construction.The key of the city eco-construction is the coordination of water resource with the city development. 相似文献
10.
Results of numerical simulation for viscous incompressible turbulent flow field over a tiny rearward facing step on circular cylinder are presented.The Domain Subdividing and Matching method and the Simplified SOLA solution are engaged in the simulation. The effects of the step's height,installed position and Reynolds number on the flow field are obtained and discussed. The results show that, if the rearward facing step is installed on the cylinder surface at a suitable point, a reattached boundary layer will be produced at the downstream of the step lagged in a small distance on the cylinder s surface and will re separate from the cylinder s surface.The reattachment point and the re separated point will exchange as the step's height and installed point exchanging.There is an effective reattachment region. If the fluid flow separated from the sharp edge of the rearward step reattaches in the effective region, the re separated point will occur at the downstream of the cross section of the cylinder and the drag will be reduced. This pattern is not directly connected with the flow in laminar nor in turbulent.[WT5HZ] 相似文献
11.
《Journal of Landscape Research》2014,(Z2)
After investigating species and application forms of ground covers in Botanical Garden of Chengdu, the application quality evaluation system was established from the perspective of ornamental, adaptive and applicable characteristics of ground covers, AHP and K-Means adopted to evaluate and grade major ground covers. The results showed that there are 93 ground cover species in Botanic Garden of Chengdu, belonging to 82 genera of 47 families. Major application means of the ground covers in the garden were introduced, covering fl ower bed, roadside, waterfront, under woods, lawn, rockery decoration. Application quality of the 38 major ground covers was evaluated comprehensively, and the qualifi cation rate achieved 97.39%, i.e. these plants are able to meet ecological, beautifying and social functions in the garden. 相似文献
12.
Deformation monitoring and control measures of a shallow buried large span tunnel constructed using the pile beam arch (PBA) method are described, taking the North Gongti Road Station of Beijing Metro line 10 as an example. Based on the monitoring datum, the crown settlement, convergence, ground settlement of the tunnel and the bridge foundation settlement are analyzed. The results show that (1) the PBA tunneling method can restrain the ground settlement and deformation of a shallow buried large span tunnel; (2) the depth, tunnel span and pilot tunnel construction may influence the deformation of a shallow buried large section tunnel significantly; and, (3) advanced conduit grouting, timely preliminary support and permanent lining construction can reduce the deformation effectively. 相似文献
13.
Cao Jiming Xia Jiliang Xin Mingdao 《保鲜与加工》1992,(6):85-91
The present paper decribes numerical analytical results of natural convection in a closed cavity partially filled with porous medium by means of Forchheimer-Brinkman model. The effects of heated rate,permeability,height of porous region,heat conduction coefficients and aspect ratio on flow and heat transfar in the cavity are systematically investigated. Velocity and temperature fields in the cavity are given and dependence of average Nu on time is obtained. 相似文献
14.
Basic on the FEM numerical analysis, the contour maps stress of rocksalt cavity's surrounding rock and the major principal stress's law changed with the depth and horizontal direction are analyzed. The influencing factors to the distribution of the stress surrounding rocksalt cavity, such as cavity's span, water pressure and the depth of rocksalt layer is also studied. The results show that major principal stress becomes big with the increase of rocksalt's depth. The cavity's influence to the stress's distribution will be clearer with the nearer to the cavity. The stress's centralization will be weaker with the accretion of water pressure in rocksalt's cavity. But the stress's centralization will be stronger, and the stress's value increases. 相似文献
15.
The 3D Goodman element is used to simulate segments' cracks in one section of shield tunnel in Guangzhou. Mechanical and deformation characteristics of segment structure responded to varied depth of cracks is analyzed in this paper. Meanwhile, research on coefficient of lateral earth pressure, soil coefficient and ground water level on mechanical and deformation characteristics is carried out. The research result shows that along with the increase of cracks' depth, the tensile stress, pressure stress reach the maximum value while the increment is not too much. However, when the depth equals to the thickness of segment, the reinforcements' tensile stress has increase sharply, even exceeded the allowable value. Moreover, the maximum number of tensile stress, horizontal and vertical convergent value of shield tunnel segment with cracks increase with the reduction of the coefficient of lateral earth pressure and soil coefficient, and increase with the increase of ground water level as well. Specific repair measure has been taken to segments' cracks in this section of shield tunnel based on the conclusions. In general, this section of shield tunnel is stable and safe now, and there is no longer new cracks appeared. 相似文献
16.
The research object is the coupled heat transfer effect between freezing soil,water and horizontal heat exchange tube,use finite volume numerical method to dispersed solving for continuity equation and heat transfer equation of unsaturated freezing soil,gives part of the temperature fields and freezing percentage distribution graphs,and analyzes the reason of the coupled heat transfer.The analysis result shows that:the temperature field of freezing soil are some horizontal lines parallelling to the ground surface.The peak value of solid-liquid phase change region appears in the upper part where there is backwater pipe,the low value appears in the place where there isn't horizontal heat exchange tube.The horizontal heat exchange tube makes the freezing front deviate towards the ground surface.The arrangement difference of inlet and outlet position of horizontal heat exchange tube will effect the size and position of the phase change region of freezing soil.Arranging the backwater pipe at one side or middle position is the optimized mode. 相似文献
17.
18.
Xia Jiliang Xin Mingdao Zhang Hongji 《保鲜与加工》1989,(5):20-26
A numerical analysis is carried out for the unsteady and steady, two-dimensional, laminar natural convection heat transfer in a square partial cavity. The partial cavity consists of two horizontal adiabatic surfaces, a vertical hot surface and a cold surface with varied opening. The results are obtained for Ra = 10~3-10~6 and Y0 = 0.0-1.0. This study shows that the opening size has significant effect on the flow and heat transfer in partial cavity, and the. extent of its effect changes with different Rayleigh numbers. 相似文献
19.
YANG Zhuan yun 《保鲜与加工》2008,(5):58-62
Pavement structures will be damaged by subgrade soil movement around the pipes introduced by extra shallow underground pipe jacking. Soil layer deformation with shallow deposits on pipes during extra shallow underground pipe jacking is analyzed using 3D FEM. The effects on pavement deformation created by the friction between shield and soil, injection slurry, jacking forces and the vehicle loads are studied with a practical project. The analytical results show that the ground surface deformation is an uplift first followed by settling with the lower part of the cover moving faster than the upper layers. It is demonstrated by comparing computational results of FEM simulation and the observed data from the in situ test that these FEM models can be applied to real world engineering. Subgrade soil settling on extra shallow underground pipe jacking in a cross section will be stable when the shield has passed through a section with a length twice the diameter of the pipe. Horizontal surface subsidence along the lateral distribution is similar to a normal distribution curve, with the primary affected areas on both sides of the axis approximately 1.5 times the diameter of the pipe. 相似文献
20.
气象因子对四川不同质地浅层土壤水分的关联分析 总被引：1，自引：1，他引：0
[目的]为了进一步预测和定量评估四川农作物区不同土壤质地类型下,气象要素对土壤水分的影响程度,[方法]利用土壤水分和气象资料,采用灰色关联度分析方法,探讨了气温、相对湿度、风速、地面温度、日照时数5个气象因子对10种不同质地类型浅层10 cm土壤水分影响情况。[结果]结果表明：各气象因子对不同质地类型的关联序不尽相同,湿度和风速对浅层土壤水分影响相对较大。无降水天气条件下,湿度和风速对砂土类和壤土类影响较大,而温度和地温对砂土类影响较小,日照对壤土类影响最小;湿度对粘土类影响最大,温度影响最小,地温次之。有降水天气条件下,湿度和风速对砂土类影响较大,气温和日照较小;各气象因子对壤土类影响各不相同,仅日照相对稳定;湿度和风速对粘土类影响最大,地温次之。[结论]因此,土壤水分的变化,应根据不同质地的类型和天气条件,找出与气象因子影响主要因素及影响程度,才能更好的掌握土壤水分变化规律,有效合理的利用土壤水分资源。 相似文献