Study On Anisotropy Of Structural Strength And Collapsible Deformation Of Loess

Loess is widely distributed in northwest China.With the large-scale development of the western region and the construction of"Belt and Road Initiative",the loess project in this area has been carried out in large quantities,and the special structure and collapsibility of loess have more and more significant influence on the project.It is necessary to study the anisotropy of loess structure strength and collapsible deformation.In this paper,the loess from Lanzhou University of Yuzhong County,Lanzhou City,was taken as the research object,and the unconfined compressive strength test and the indoor collapsibility test were carried out on the samples with different angles from the deposition surface.The anisotropy of structural strength and collapsible deformation of the loess is analyzed,and the following conclusions are drawn:With the increase of water content,the stress-strain curve of undisturbed loess gradually changes from strain softened type to strain hardening type,and its unconfined compressive strength decreases with the increase of water content.When the moisture content is the same,the strength q of the sample at 30 °angle with the deposition surface is the smallest,and the law of q30°<q45°?q60°<q0°<q90°.The lower the moisture content is,the more significant the regularity is,which indicates that the anisotropy of the strength is stronger.As the water content tends to saturation,the anisotropy decreases gradually.The anisotropy of the remolded loess is the same as that of the original loess,but the unconfined compressive strength and anisotropy of the remolded loess are weaker than that of the original loess under the same conditions.(2)when the moisture content is low,the initial compression modulus of undisturbed loess is larger,and the initial compression modulus decreases with the increase of moisture content.When the moisture content is the same,the initial compression modulus of the sample at 30°angle with the deposition surface is the smallest,and the law of E30°<E45°<E60°<E0°<E90°.The compression modulus in other pressure sections is the same as the initial compression modulus However.when the pressure exceeds a certain critical pressure,the anisotropy of the compression modulus gradually disappears.When the moisture content is 2%and 5%,the anisotropy of compression coefficient a1-2 is not obvious.With the increase of moisture content,the compressibility increases gradually,and the anisotropy of compression coefficient a 1-2 increases gradually,and shows an inverted "U"relationship(a90°<a0°<a60°<a45°<a30°).However,when the moisture content exceeds a certain limit moisture content,the isotropism of compression coefficient a1-2 decreases gradually.(3)When the moisture content is low,the collapsibility coefficient of undisturbed loess is larger,and the collapsibility coefficient decreases with the increase of moisture content.Both the self-weight collapsibility coefficient and the collapsibility coefficient at 200 kPa,300kPa have anisotropy,and show the law of ?30°>8 45°>?60°>?0°>?90°.(4)Through the compound power index model,the stress-strain curves obtained from the tests of different moisture content and different sampling angles are fitted,and the correlation coefficients are close to 1,which shows that the model can describe the corresponding stress-strain curves.And applied to the analysis of loess anisotropy.