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分析传统空间Mohr应力圆理论,并指出该理论不能完全反映双向受力下(即考虑中间主应力时)岩土类摩擦材料的应力状态。试验表明岩土类摩擦材料包括混凝土、岩石和土体在双向受压下(以压为正,此时σ_3=0)抗压强度大于单向受压(此时σ_2=σ_3=0)抗压强度,由此提出双向受力状态下2个主剪切平面上承载能力比单向受力状态下剪切平面上的承载能力大,其原因在于双向受力状态下的法向应力大于单向受力下的法向应力,从而使摩擦力和黏聚力增大。这表明空间应力状态下最大压应力σ_1随σ_2增大而增大,此时Mohr圆也随之增大。当σ_2从σ_2=σ_3=0增大至σ_2=σ_1时,不仅2个小极限应力圆在变动,而且3个极限应力圆都在不断增大,由此建立适应双向受力下岩土类摩擦材料的空间Mohr应力圆理论。考虑上述特性,将基于传统空间Mohr应力圆理论的等强度能量强度准则发展为变强度能量强度准则,这一准则能很好地反映岩土类摩擦材料在双向受力条件下的强度特性。
The traditional Mohr stress circle theory is analyzed, and the theory can not fully reflect the stress state of the geomaterials under the bi-directional stress (that is, when the intermediate principal stress is considered). The tests show that the compressive strength of rock-soil friction materials including concrete, rock and soil is greater than that of uniaxial compression (σ_2 = σ_3 = 0) under the bi-directional compression (with positive pressure and σ_3 = 0 at this time) Therefore, it is proposed that the bearing capacity of two main shear planes under two-way stress is larger than the bearing capacity of shear plane under unidirectional stress. The reason is that the normal stress under bi-directional stress is larger than that under unidirectional stress The normal stress under force, so that the friction and cohesion increased. This indicates that the maximum compressive stress σ_1 in space stress state increases with σ 2, and the Mohr circle also increases. When σ_2 increases from σ_2 = σ_3 = 0 to σ_2 = σ_1, not only the two small ultimate stress circles change, but also the three ultimate stress circles increase continuously, so the geotechnical friction Material space Mohr stress circle theory. Considering the above characteristics, the criterion of equal strength energy intensity based on the theory of Mohr stress circle in the traditional space is developed as the variable strength energy intensity criterion, which can well reflect the strength characteristics of the geotechnical friction material under bi-directional stress.