[求助]紧急求助：Adina中如何设置接触单元？

bigeyeqiao

I want to model soil-structure interaction in ADINA with an initial stress state in the soil.  The structural elements are beams that are below the ground surface.  The soil-structure interface is model with contact elements.  I plan to obtain the stress state in the soil by applying gravity, but applying gravity causes deformations in the soil which produces separation between the structure and the soil.  The separation prevents obtaining correct contact forces between the soil and the structures.  How can I apply gravity but allow my structure to deform with the soil so that no gaps develop.
这是个边坡挡土墙的稳定性问题，首先打桩，然后挖除半边土体，用adina分析土体与桩相互作用，用2D实体单元模拟土体，用梁单元模拟桩。土体与桩之间用接触单元（adina默认的设置）。通过对土体施加重力来获得初始应力状态。问题就是，在施加重力后，土体与桩产生了分离，而无法继续计算土体与桩之间的受力情况。请问，如何应如何设置，以保证在施加重力后，桩会随着土体一起变形，不产生分离。


图1：This is a better status, more realistic situation
这是比较正常的情况，在顶端会发生分离，但是底部还是相互接触的


图2：Wall model, geometry and meshing, before gravity application
这是施加重力之前的模型和网格划分。


图3：Deformation of soil due to gravity, note the deformation so soil away (down) from the pile
施加重力后，土体产生变形，土与桩产生分离


图4：Magnified deformation of soil and pile after gravity application and excavation
挖掉半边土之后，变形情况更清楚：

bigeyeqiao

估计是接触单元的问题，还请高手指点！！小弟感激不尽！