Structural Strength Deterioration Characteristics and a Model of Undisturbed Loess under the Action of Wetting and Freeze‐Thaw Cycles

Abstract

Undisturbed loess is affected by external environmental disturbances, such as wetting and freeze-thaw cycles, which cause microstructural changes that have an important impact on the structural strength of the loess. These changes in turn affect the stability of structures such as embankments, slopes, and guards. This article takes the Q3 undisturbed loess in Lintong District, Xi’an, as an example. The effects of wetting and freeze-thaw cycles on the loess expansion ratio and pore structure were studied by wetting tests, freeze-thaw cycle tests, and scanning electron microscopy (SEM). The changes in the compression index and compression modulus were studied by a confined compression test. The loess e-lgp compression curve was obtained according to the confined compression test, and the newly defined concepts of the loess structural strength, residual structural strength, and structural strength damage variable, in addition to the e-lgp compression curve, were combined with the experimental data to calculate the damage value generated by the disturbance during the sampling and preparation of loess. The deterioration of the structural strength and damage variable of loess was analyzed. Based on the microscopic statistical damage theory and Weibull distribution, the model used the volume expansion ratio as a variable to establish a statistical damage model under wetting and freeze-thaw cycles. Finally, on the basis of the test, the model parameters were determined. The models were verified by taking loess from a foundation pit in the northern suburbs of Xi’an and were in good agreement with the results of the test. Ultimately, the models have good practicability and can provide guidance for engineering design and construction.

Effect of Mica Content on Mechanical Properties of Yili River Valley Loess under the Impact of Freezing and Thawing

“…The impact of the water content, temperature, and other variables on the mechanical strength of frozen soil was further investigated using the mechanical characteristics of several types of soil [13][14][15]. The microstructure of the soil mass and the micro-structural change in the loess due to FTCs had a significant effect on the structural strength of the loess [16][17][18][19]. Different scholars had different opinions on the alteration in the mechanical strength of the soil mass under FTCs.…”

Effect of Freeze–Thaw Cycles and Initial Water Content on the Pore Structure and Mechanical Properties of Loess in Northern Shaanxi

“…They also explored the correlations between the mechanical strength and the meso-structures of the remodeled loess. She et al [21] studied the pore structures of loess after freeze-thaw cycles using scanning electron microscopy technology, and they analyzed the changes in their structural strength to establish a relevant statistical damage model. Xu et al [22][23][24][25] obtained the strength parameters and microfine structural parameters of loess soil samples using CT scans, SEM tests, and triaxial shear tests.…”

Effects of Dry–Wet Cycling and Temperature on Shear Strength and Microscopic Parameters of Coal Measure Soil

“…Moreover, surface-crack occurrence and development in rock soil are generally related to dry-wet cycling [8,9]. Furthermore, dry-wet cycling is a crucial reason underlying the deterioration of microstructure and macro mechanics of a wide range of unsaturated soils, such as expansive soil [10,11], loess [12], and red clay [13,14]. In recent years, researchers have also studied the C-M-S strength characteristics subjected to dry-wet cycling [15,16].…”