It is ancient origin, and its composition is complex.

且起源古老，成分复杂。

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However, for the composite load has the characteristics of complex composition, random time variance and spread over different area, its exact mathematics model is still not built up.

然而，系统中的综合负荷，由于具有构成复杂、随机时变、地域分散等特点，其准确的数学模型一直没有建立起来。

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Mixture soil is a kind of the special soil, its complex in composition, a great disparity in size, a great change in mechanics quality.

“混合土”是一种特殊性土，成分复杂，粒径悬殊，力学性质变化较大。

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