群桩变形计算的方法有疑 [复制链接]

现行建筑桩基技术规范JGJ94-94规定了群桩变形计算的方法，十分明确。请问： {@! Kx`(:  
1、承台下桩及土视为基础，是何种原因？桩与桩周土同位移变形，桩周土能对桩发挥侧阻力吗？这与承载力设计的桩周土发挥重要功能岂不互相矛盾？ O$/o'"@ /  
2、按此方法如何确定压缩层下限？对于长桩基来说，采用此法确定的压缩层下限是否偏深？

是哦，论说变形的话，桩身本身应该也有一定的变形吧

正因为侧阻力发挥作用，桩本身才能带动土体位移，若分开考虑两者位移，条件太多，计算的复杂程度不可想象，规范中如此规定也许是种模糊算法，若要计算群桩沉降，控制性钻孔的深度要控制好，所以有些高层建筑的钻孔可达一百多米。

正因为侧阻力发挥作用，桩本身才能带动土体位移 I`NjqyTW  
这是桩侧土工作的实际表征与客观反应，是符合工程实际的。但是： U&O: _>~  
L3CP`cx  
群桩变形计算的模式却背其道而行之，认为桩土共同往下发生位移，其相对之间无位移及任何位移趋势，这才能产生变形。 E>l~-PaZY  
\rv<$d@L  
这种变形计算的模式与承载力取值的模式为何要互相矛盾与冲突而不能自圆其说？

才学浅薄，目前不能够回答，敬请见谅！好好学习相关资料后，再来回答！

桩基规范对桩基承载力验算与变形验算的假定条件不一致，我纳闷？

今天又长见识了！

承台下桩及土视为基础，是何种原因？桩与桩周土同位移变形，桩周土能对桩发挥侧阻力吗？这与承载力设计的桩周土发挥重要功能岂不互相矛盾？

For the deformation calculation in pile group,  the force transfer path is used here. They consider dO! kk"qn  
*av<E  
pile and soil inside of pile group work together and use the force transfering angle to decide the B9jC?I |`  
h+g_rvIG*  
under layers.  The soil surrounding pile group area  support the pile and soil inside of pile group. @=}0`bE  
l<58A7   
For the group pile capacity, they use individual pile and add the pile group effect. The idea just spH7 /5}  
IL#"~D?
  
continue  from single pile design. hF~n)oQ  
Rq'S>#e  
Different ways and ideas for two calculations, it is a little bit hard to understand. But both are correct. "c
%0P"u  
=(j1rW!  
BTW: in the beam design, the force transfer path also be used now in some countries.

承台下桩及土视为基础，是何种原因？桩与桩周土同位移变形，桩周土能对桩发挥侧阻力吗？这与承载力设计的桩周土发挥重要功能岂不互相矛盾？

In cohesionless soil, the settlement of group of piles is usually small and they occur fairly rapidly. EU/C@B2*Dl  
1hY{k{+o  
In cohensive soil,  the long-term settlement of group of pile in clay is calculated using the method employed in estimating settlement of shallow foundations(the soil inside of pile group area stick to the pile and work with pile, something like H-pile side resistance calculation case). mp1@|*Sn  
pK>N-/?a  
This group settlement is the displacement related to the under layer soil below the "shallow foundation".  C2kPMB=Xo  
G5BfNU  
In the bearing capacity, the side resistance is due to the displacement between pile and the soil around pile. :D5R
lfj  
L\J;J%fz.  
Do not confuse these two displacements.

承台下桩及土视为基础，是何种原因？桩与桩周土同位移变形，桩周土能对桩发挥侧阻力吗？这与承载力设计的桩周土发挥重要功能岂不互相矛盾？