Finite element analysis of the double-spring foundation model

Finite element analysis of the double-spring foundation model Wen Xingwu, Yang Xueqiang, Kong Lingxia, He Shixiu Department of Civil Engineering, Hubei Institute of Technology. Wuhan, Hubei, 43,68 should be based on the relationship between the unloading modulus of the soil in the softness of the interior of the soft 1 test, the vertebral 4 plant is suitable for increasing the finite element double, the Dunsson foundation spring coefficient

Finite element analysis of the double-spring foundation model Wen Xingwu, Yang Xueqiang, Kong Lingxia, He Shixiu Department of Civil Engineering, Hubei Institute of Technology. Wuhan, Hubei, 43,68 should be based on the relationship between the unloading modulus of the soil and the ground-loading modulus of the soft 1 test. The 4th plant is suitable for increasing the finite element double, the formula of the Dunsson foundation spring coefficient, for the foundation pit Step-by-step excavation and support structure design and calculation of soft soil tunnel construction and other geotechnical projects have great practical value.

Qing key word double spring model; unloading modulus; incremental finite element; foundation spring coefficient, classification number 472 document identification code, 4 in the calculation of foundation pit excavation and tunnel application in soft soil area, The displacement of the surrounding strata caused by pit excavation or tunnel construction and the resulting damage to buildings and underground pipelines cannot be accurately calculated. The results obtained by the existing calculation methods are still relatively thin. Muwen deduced the formula of the spring coefficient of the foundation with the incremental finite å…€ double spring model. It is suitable for the calculation of the foundation blasting coefficient of the foundation pit excavation process and the displacement of the supporting pile and the active and passive side. Derivation of force calculation formula 1. Derivation of soft soil unloading modulus 1.1.1 Unit division unit division is as small as 1 and the pile is divided into units by 1 unit, then there are + 1 knot.

Pile, force model 1.1.2 active side earth pressure and displacement 1 恪 pile side seat resistance of the multi-sounding response from the active side vertical direction constant ice level to reduce unloading. For each step of excavation, the following formula is used to change the soil to the vertical direction stress of the soil at the node.

For example, for the effective internal friction angle of the soil, each calculation is completed and assigned as the initial value of the next step of excavation.

The earth spring at the knot node produces an active lateral earth pressure increment, that is, the incremental force generated by the active side soil spring being stretched by the tensile force.

The displacement of the pile at the knot node is 1.3. The passive side earth pressure and displacement 2 are the thickness of the soil at the knot node, which varies with excavation.

The initial value is 2, the peak is the passive side earth pressure stress increment. After each calculation, the +妒 value is given as the initial value of the next step excavation.

Consider the calculation formula of the unloading modulus of the stress path. Describe by the hyperbola under soft soil.

1.2 Derivation of horizontal resistance coefficient In the finite element analysis of the bar system, the horizontal resistance coefficient is a very important and particularly sensitive coefficient. More commonly used people before.

The evaluation method is Zhang Youling Law 1 and E. BowIes Method Jin Bing 2 pairs. The 1 method was reasonably revised. Zhang Youling Law. The method and 1 do not consider the size effect of the pressed area. K`Bowles also only has an empirical method. In essence, 4 is not only related to soil quality, but also related to the unloading modulus test and parameters of the compressed area size effect Hou Xueyuan 4 soft soil. The formula to advance the value of the discussion is asked.

Set a soil spring to generate the concentrated force as only, the area of ​​the spring on the pressed soil body is the slope protection, the diameter, and 6 is the length of the division unit pile segment. The distributed pressure bow analysis is obtained for Equation 10, and the slope of the stress-strain curve at any point on the curve is obtained. , e3 Zhang Rongtang 1 thinks that the foot stress increment ratio is the general relationship between the tangent linear modulus and the stress axis strain curve under the path. The 1 is the constant response, the increase ratio is the volume change, and the axis is the axial direction. Strain increment. After derivation, the final tangential modulus is obtained as follows. The upper stress is less than the horizontal main response. According to the 3,18,89 solution, the displacement under the action is 5, and the corresponding horizontal resistance coefficient is the formula 12, which can be used. The following formula is obtained: When the vertical principal stress is less than the horizontal principal stress, the initial unloading modulus of the 7l+P, U2M 2 gray muddy clay is kibl2w when the vertical principal stress is not less than the horizontal principal stress, and +si, h3II mountain Liu Guobin soft soil unloading 1 model 4, with an average 纟1 card with 0, a number of cobalt to increase the force. The initial unloading modulus of various stress paths increases linearly. After linear fitting, the following relationship can be regarded as the initial unloading modulus value of the deep foundation pit excavation project, which is the stress path and the axis. The constant load, radial unloading, can be taken as =106.4; the passive side can be regarded as the initial unloading deformation modulus under the three types of loads, that is, axial unloading and radial loading. The core can be taken as the stress path 即 0.0, that is, the axial unloading, the radial loading, the ratio of the axial unloading amount to the radial loading amount, and the ratio of the axial stress unloading amount to the radial loading amount of the 15 stress path is 1. The ratio of the axial unloading amount to the radial loading amount of the stress path 2.0 is 2 according to the experiment of the unloading modulus of Liu Guobin's gray silty clay, which can be regarded as human load on the active side and the horizontal load is unchanged. , vertical unloading. The soil is inflated. Thus, on the passive side, it is considered; class load. The water is loaded, the vertical direction is unloaded, and the soil is shear-shrinking. At this time, the saturated clay is consolidated, as in the case of 1.151.20, which is the value of the tangent modulus of the soil in the state of failure. call.

1.0, the initial tangential modulus coefficient when the soil is dilatant, the normal solidified saturated clay, the value is generally in the range of 0.400.55; the day is the strength of the degree of play, the value is between 01. Take the heart of 1.15, =0, machi = 1.0, and = 07 intensity of the performance of 7 off; then the active side is desirable, = 0.85; for the passive side can be taken = 1.05; for the foundation pit excavation project in the city, the impact is stable Sexually saturated soft and saturated fine sand is a soft and weak soil. Most of the 1-body units in the pit are mainly dilatant, and the Poisson's ratio is taken as. 3. Which is the number of force, according to the literature 5, and choose for the circular section you can take, 79., love the dust, pull, the internal friction angle of the soil. According to the test, the test is 0.850.95, which can be approximated as 09. The vertical principal stress of the bow has lost the maximum principal stress. The significance of the minimum principal stress has been lost from the horizontal principal stress of the formula 1 and the formula 3. The formula 2 and 4 6 outside the formula is determined.

3 Example 1 For a foundation pit engineering pile 15 agricultural bored pile, the elastic modulus of reinforced concrete = 2.67, and the pile length is divided into units per meter. , diameter 1., the inter-pile is 1.5m, the gray silt clay soil weight V = l7.lklNn Poisson's ratio = 0.3. It is preferable for the active side, = 0.85; the passive side can be taken = 1.05; Take 0. 9. Step without excavation, excavate 3 yang each time, calculate the horizontal to ground spring coefficient of each node on the passive side of the foundation pit before excavation. The horizontal and vertical ground spring coefficients of the active and passive sides before excavation are equal. 2 The first step of sweat is to dig after the Lord. The horizontal side of the wave side is the spring coefficient 怂 and 3, 4. Among them, series 1 is the active side horizontal foundation spring coefficient, and series 2 is the passive side horizontal ground spring coefficient. After the first and the second excavation, the body water 1; the moment, and the Lord. The fluctuation side soil card force, the calculation result 121 is divided into 1. yuan, and the pile length 15 can be divided into 16 nodes. Series 1 is the finite element calculation value of the rod system, and Series 2 is the theoretical value of the Rankine earth pressure, the same below.

There are several nodes, series 1 series 2 IlII step excavation 1 active 1; the horizontal anti-inhibition coefficient obtained by Liwen is very suitable for numerical analysis. For example, using the incremental finite element method, the pre-step excavation stress path is calculated by the program. Soil model and horizontal resistance coefficient are used for step calculation. When the step size is small, the error is negligible. From the calculation results of the example, this paper proposes that the double-elastic yellow foundation model is feasible for the calculation of deep foundation pit support.

4 Conclusion The horizontal resistance coefficient at each node of the retaining pile is not only related to soil quality. It is related to the super-money of the road and the unloading modulus of the soft soil. The horizontal resistance coefficient of the foundation increases with the depth of 1 and the horizontal resistance of the passive side increases. Zhang Rongtang. Determination of the constant stress ratio of the path nonlinear elastic parameters is determined in the doctoral thesis chapter. Chinese Academy of Sciences, 2000.

Jin Yabing. The finite line element method is applied to the calculation of the anchor pile support system by Yang Xueqiang. Finite element analysis of the rod system for deep foundation pit support. Hubei Worker Liu Guobin, Hou Xueyuan. The unloading modulus of soft soil. Journal of Geotechnical Engineering, South China University of Technology. Foundation and foundation elbow. Beijing China Building Industry Press, 1991.

Responsible editor Zhang Yanfang

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