水位變幅對地下框架結(jié)構(gòu)作用效應敏感性分析
發(fā)布時間：2018-09-11 13:24
【摘要】：山區(qū)河道城市化前溪流深切,城市化后天然河流與周邊地塊存在較大高差,設計從防洪、水生態(tài)等多目標出發(fā),提出了適應山區(qū)城市的雙層河道建設方案:上層明渠、下層暗涵。其中,下層暗涵河道在場平過程中深埋地下,維護、檢修困難且事故后果嚴重,因此對其結(jié)構(gòu)受力特性的掌握尤為重要,在設計階段加以考量能有效降低其事故風險�；靥顖鰠^(qū)的地形、滲透特性使得強降雨條件下涵周土體內(nèi)地下水環(huán)境會發(fā)生劇烈變化,土體若長時間呈沁水飽和狀態(tài),對場區(qū)的構(gòu)筑物極為不利,因此考慮將外水通過涵體透水通道導入下層河道向下游排出,此時結(jié)構(gòu)將會遭遇地下水水位變化這一工況�，F(xiàn)行規(guī)范通過載荷—結(jié)構(gòu)方式計算水荷載時通常進行折減或采用可能的最大水位,而涵體受力實質(zhì)是與滲流—應力雙場耦合作用下的涵周土體共同變形的過程,因此,研究深埋地下框架結(jié)構(gòu)在地下水位變化所產(chǎn)生的流固耦合效應作用下的受力特性具有重要的工程應用價值。本文依托工程實例建立了地下框架結(jié)構(gòu)三維有限元模型,主要研究內(nèi)容如下:(1)從基本理論有效應力原理和達西定律出發(fā),推導了應力場、滲流場的控制方程:應力平衡方程和非穩(wěn)定飽和滲流連續(xù)方程,并給出相應的定解條件。根據(jù)兩場相互作用的的影響方式,得到了多孔介質(zhì)土體滲流場應力場耦合的數(shù)學模型并給出了耦合狀態(tài)下的有限元矩陣格式和求解方式。闡述了三維有限元模型建立過程中的要點,并依托實例工程地勘報告和相應土工實驗成果給出模型參數(shù)。(2)模擬分層回填施工過程,其涵頂存在應力集中現(xiàn)象,此為深埋框架結(jié)構(gòu)所特有的受荷形式;模擬水位下降固結(jié)過程,其有效應力的增長由產(chǎn)生明顯水位降前(主要)、明顯水位降落過程、涵側(cè)水位降落過程三階段階段的孔壓溢出、沉降差(35)h產(chǎn)生的應力集中共同貢獻,此時水位降幅快慢并不適用來衡量內(nèi)力變化的趨勢。固結(jié)排水過程使得沉降加劇、內(nèi)力增大,結(jié)構(gòu)受荷破壞的風險相應增大。(3)回填材料對涵體受荷以及內(nèi)力響應影響較大的因子為彈性模量E以及滲透系數(shù)k,不考慮涵背回填、涵側(cè)排水工程措施時,僅存在土石混合料的單參數(shù)作用下,場區(qū)回填料彈性模量E_m越大、滲透量級較高時滲透系數(shù)K_m相對越小結(jié)構(gòu)越有利;反之,引入涵背砂礫石回填料,其彈性模量E_s、滲透系數(shù)k_s,在多參數(shù)作用下,E_m越小、E_s越大、K_m大于并接近k_s、k_s越小時,對結(jié)構(gòu)越有利,其中,在相同的變化量級范圍內(nèi),E_m比E_s更敏感,k_s比K_m更敏感�？傮w來說,在涵側(cè)土體范圍內(nèi)采用相應工程措施能有效減小結(jié)構(gòu)受荷及內(nèi)力大小,且更為經(jīng)濟高效。
[Abstract]:Before the urbanization of mountain rivers, the rivers are deep, and there is a great difference in height between the natural rivers and the surrounding land blocks after urbanization. From the multi-objectives of flood control and water ecology, this paper puts forward the construction scheme of the double-layer river channels suitable for mountain cities: the upper open canal, the open channel in the upper layer, and so on. The lower culvert. Among them, the underground is buried deeply in the course of the hidden culvert in the course of site leveling, the maintenance is difficult and the accident consequence is serious. Therefore, it is very important to master the mechanical characteristics of the structure, and the risk of the accident can be effectively reduced by considering it in the design stage. The topography and permeation characteristics of backfill site make the groundwater environment of culvert surrounding soil change dramatically under heavy rainfall. If the soil is saturated with water for a long time, it will be very unfavorable to the structure of the field area. Therefore, it is considered that the external water will be discharged from the lower river through the culvert permeable channel, and the structure will be subjected to the condition of groundwater level variation at this time. In the current code, the maximum water level is usually reduced or the maximum water level is adopted when calculating the water load by load-structure method, and the stress of culvert is essentially the process of deformation of soil around culvert under the coupling of seepage and stress, so, It has important engineering application value to study the mechanical characteristics of deep buried underground frame structure under the effect of fluid-solid coupling caused by the change of groundwater level. In this paper, a three-dimensional finite element model of underground frame structure is established on the basis of engineering examples. The main research contents are as follows: (1) the stress field is derived from the basic theory of effective stress principle and Darcy's law. The governing equations of seepage field are stress balance equation and unsteady saturated seepage continuity equation, and the corresponding definite solution conditions are given. According to the influence mode of the interaction of two fields, the mathematical model of the coupling of seepage field and stress field in porous media is obtained, and the finite element matrix format and the solution method under the coupling state are given. The main points in the process of establishing 3D finite element model are expounded, and the model parameters are given based on the geological prospecting report of practical engineering and the corresponding geotechnical experiment results. (2) the stress concentration phenomenon exists in the culvert top of the culvert when the construction process of layered backfill is simulated. This is the special loading form of the deep buried frame structure, and the increase of effective stress is caused by the pore pressure overflow in the three stages of the water level descending process, the obvious water level falling process and the culvert side water level falling process, and the increase of the effective stress in the simulated water level descending consolidation process is mainly caused by the obvious water level drop (mainly). The stress concentration caused by the settlement difference (35) h contributes together, and the water level decline is not suitable to measure the trend of internal force change at this time. During consolidation and drainage process, settlement intensifies, internal force increases, and the risk of structural damage under loading increases accordingly. (3) the factors which have a great influence on the response of culvert and internal force are elastic modulus E and permeability coefficient k, and the backfill is not considered. In culvert drainage engineering measures, under the action of only one parameter of earth-rock mixture, the larger the elastic modulus E _ m of backfill in field area is, the more favorable is the structure of permeability coefficient km _ m when the order of permeability is higher; The smaller the ESM is, the bigger the KSM is, the smaller it is and the smaller it is, the smaller the structure is, the more favorable the structure is to the structure. In the same range of variations, Em is more sensitive than ES, and KS is more sensitive than KM. In general, using the corresponding engineering measures in the range of the culvert soil can effectively reduce the load and internal force of the structure, and it is more economical and efficient.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TV31
本文編號：2236809
[Abstract]:Before the urbanization of mountain rivers, the rivers are deep, and there is a great difference in height between the natural rivers and the surrounding land blocks after urbanization. From the multi-objectives of flood control and water ecology, this paper puts forward the construction scheme of the double-layer river channels suitable for mountain cities: the upper open canal, the open channel in the upper layer, and so on. The lower culvert. Among them, the underground is buried deeply in the course of the hidden culvert in the course of site leveling, the maintenance is difficult and the accident consequence is serious. Therefore, it is very important to master the mechanical characteristics of the structure, and the risk of the accident can be effectively reduced by considering it in the design stage. The topography and permeation characteristics of backfill site make the groundwater environment of culvert surrounding soil change dramatically under heavy rainfall. If the soil is saturated with water for a long time, it will be very unfavorable to the structure of the field area. Therefore, it is considered that the external water will be discharged from the lower river through the culvert permeable channel, and the structure will be subjected to the condition of groundwater level variation at this time. In the current code, the maximum water level is usually reduced or the maximum water level is adopted when calculating the water load by load-structure method, and the stress of culvert is essentially the process of deformation of soil around culvert under the coupling of seepage and stress, so, It has important engineering application value to study the mechanical characteristics of deep buried underground frame structure under the effect of fluid-solid coupling caused by the change of groundwater level. In this paper, a three-dimensional finite element model of underground frame structure is established on the basis of engineering examples. The main research contents are as follows: (1) the stress field is derived from the basic theory of effective stress principle and Darcy's law. The governing equations of seepage field are stress balance equation and unsteady saturated seepage continuity equation, and the corresponding definite solution conditions are given. According to the influence mode of the interaction of two fields, the mathematical model of the coupling of seepage field and stress field in porous media is obtained, and the finite element matrix format and the solution method under the coupling state are given. The main points in the process of establishing 3D finite element model are expounded, and the model parameters are given based on the geological prospecting report of practical engineering and the corresponding geotechnical experiment results. (2) the stress concentration phenomenon exists in the culvert top of the culvert when the construction process of layered backfill is simulated. This is the special loading form of the deep buried frame structure, and the increase of effective stress is caused by the pore pressure overflow in the three stages of the water level descending process, the obvious water level falling process and the culvert side water level falling process, and the increase of the effective stress in the simulated water level descending consolidation process is mainly caused by the obvious water level drop (mainly). The stress concentration caused by the settlement difference (35) h contributes together, and the water level decline is not suitable to measure the trend of internal force change at this time. During consolidation and drainage process, settlement intensifies, internal force increases, and the risk of structural damage under loading increases accordingly. (3) the factors which have a great influence on the response of culvert and internal force are elastic modulus E and permeability coefficient k, and the backfill is not considered. In culvert drainage engineering measures, under the action of only one parameter of earth-rock mixture, the larger the elastic modulus E _ m of backfill in field area is, the more favorable is the structure of permeability coefficient km _ m when the order of permeability is higher; The smaller the ESM is, the bigger the KSM is, the smaller it is and the smaller it is, the smaller the structure is, the more favorable the structure is to the structure. In the same range of variations, Em is more sensitive than ES, and KS is more sensitive than KM. In general, using the corresponding engineering measures in the range of the culvert soil can effectively reduce the load and internal force of the structure, and it is more economical and efficient.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TV31
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