对桩基承载力设计的一点疑问 [复制链接]

1、现行桩基规范，无论何种桩型，其承载力设计时的桩基承载力一般由桩侧和桩端土层提供反力几何累计而成，而这些参数是根据各土层的性状直接提供，根本未考虑桩基实际的工作状态。 = ^_4u%}  
2、无论你计算的是保守还是冒进，无论你如何符合规范的条款，桩基承载力验收基本以抽样试验来确定。 J4q_}^/2w  
3、上次讨论的厚层粘性土层中长桩受力并不是各区段同期均匀受力工作，而是一般桩顶先工作，中间段次工作，底部桩侧土可能未进入工作；或者是桩端直接工作，桩侧根本无法工作等，这些现象说明，按以上条款设计桩基承载力与桩的实际工作状态相差是很大的，即使通过桩基验收的成品桩，也不一定与设计初衷相匹配。
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4、那为何要按第一条进行桩基承载力设计呢？这种设计有指导意义吗？

也许是经验吧

经验？不管是不是与实际吻合，吻合程度不管怎样，都可以进规范，进行桩基计算，指导工程实践？

获益匪浅啊！

为何要按第一条进行桩基承载力设计呢？这种设计有指导意义吗？

Actually, you talk about the pile design mechinism.  Please notice,  the value  of bearing capacity _2E*  
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is  "Ultimate" or "Design" value. All these methods are based on pile failure (resistance).  It is yHjuT+/wM,  
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bearing capacity. One of the most unsafe status is the  side resistance and tip resistance t @vb3  
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working together.  Of course, the `T(T]^C98  
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settlement  should be reasonable (that's why it need settlement calculation in design). vG'I|OWg  
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The sampling is general idea for real condition conformation even though the soil layers are not :DoE_  
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absolutely the same. Before sampling, the pile in most unsafe position is choosed for sampling.

the methods of pile design should be established on the actual envirement of the pile working. d_aHUmI^"  
but the methods in CODE now is not accordance with the actuality, K4K]oT  
why????

进行桩基计算，指导工程实践

厚层粘性土层中长桩受力并不是各区段同期均匀受力工作，而是一般桩顶先工作，中间段次工作，底部桩侧土可能未进入工作；或者是桩端直接工作，桩侧根本无法工作等，这些现象说明，按以上条款设计桩基承载力与桩的实际工作状态相差是很大的，即使通过桩基验收的成品桩，也不一定与设计初衷相匹配。

How about the final work status? How about the load distribution curve along the pile ? x
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The skin friction occurs due to relative displacement between soil and pile. As you said, the upper part of pile work first. The skin friction at this point may also be negative skin friction when the clay has big settlement.  That is the  neutral plane coming from. o9]i {e>L  
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When the external load is quite small, it will be carried by the upper part. Do not forget, when you  design the pile, it is the ultimate value or design value(considering safety of factor) X;7hy0Y  
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The load test is used to make sure the design. B!1Bg9D  
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I have some load test data and  strain gage in the pile (constructed in clay,about 25m) to monitor the load  distribution in the pile. pj#ls  
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The design method is absolutely correct. K7c[bhi_w  
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Welcome to discuss!

The design method is absolutely correct. ve^gzE$<I  
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I mean for the design mechanism: skin resistance and tip resistance method. Q?>DbT6  
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The different part of pile work together in the final.