Elastic Analysis of Nonhomogeneous Frozen Wall under Nonaxisymmetric Ground Stress Field and in State of Unloading

Abstract

The mechanical analysis of frozen walls is a cornerstone technology of artificially frozen ground. The mechanical response of frozen walls is affected by heterogeneity, excavation unloading, uneven ground pressure, and the characteristics of surrounding rock. However, these factors are rarely taken into full consideration in existing analysis models. To address this shortfall, this study presents a plane-strain model that considers the inhomogeneity of frozen walls, the unloaded state of the frozen-wall inner edge, and the nonuniform ground stress field (abbreviated as “IF model”). The solution of the IF model is based on the superposition of thin concentric cylinders under two types of contact conditions: complete contact and smooth contact, and its validity is tested by a finite-element calculation. The calculation indicates that the excavation reduces the radial force and increases the tangential force between the frozen wall and the surrounding earth mass; the ground principal stress is rotated after the excavation. If the radial unloading equals the tangential unloading at the inner edge of the frozen wall, the response of the radial stress differs from that of the tangential stress at the outer edge of the frozen wall. The circumferential stress and the radial displacement at the inner edge correlate linearly with the nonuniform coefficient of the ground press and the unloading ratio. If the nonuniform coefficient is relatively small, the inner edge of the frozen wall may incur tensile damage. Compared with the model of a homogeneous frozen wall (abbreviated as “HF model”), which has a uniform temperature distribution, the absolute value of the circumferential stress is lower (higher) for the IF model where the temperature is above (below) average. When the frozen wall is relatively thick, the circumferential stress of the inner edge of the frozen wall is lower for the IF model than for the HF model. The percent reduction is 8.12%∼9.32% for rock freezing and 13.41%∼18.03% for soil freezing. The IF model proposed herein thus reflects the characteristics of frozen walls and surrounding rock more clearly and accurately than the HF model and obtains stress states closer to the reality. Therefore, the IF model is recommended for the design and construction of frozen walls.

Experimental Study on Influencing Factors of Characteristic Index of Local Horizontal Frozen Body of Double‐Row Pipe under Seepage

“…According to previous research studies [6,19], the horizontal frozen body formation process under the effect of seepage can be divided into three stages. Firstly, the second row (last row) of the frozen soil column overlapped.…”

“…Until now, a lot of research studies have been performed on the stratum freezing technology [1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19], but some limitations still exist. Firstly, when they are used to study the development law of the frozen wall under the seepage, most of the model tests are the single-row-pipe frozen one.…”

Calculation Method of the Design Thickness of a Frozen Wall with Its Inner Edge Radially Incompletely Unloaded

“…Removing Domke's limitation on the outer radius of the frozen wall plastic zone, Sanger [15] proposed a fully plastic single-layer, thick-walled cylinder model formula. Recently, there has been a surge in the utilization of unloading models to enhance the analysis of frozen walls [16][17][18][19][20]. Because the Domke formula has large errors when the modulus ratio of the frozen wall to its surrounding unfrozen alluvium is less than 10, Yang [17] started with the geostress unloading mechanism and presented a formula that comprehensively considered the excavation unloading effect, the interaction between the frozen wall and the surrounding unfrozen alluvium, and Domke's limitation on the outer radius of the frozen wall plastic zone.…”

Research on the Elastoplastic Theory and Evolution Law of Plastic Zone Contours of Horizontal Frozen Walls under Nonuniform Loads

“…However, in recent years, several scholars have used an unloading model to optimize their study of the mechanical properties of the frozen wall [8][9][10]32,33], which has led to suitable results. Nevertheless, analyses based on the elastoplastic theory for frozen walls using the excavation unloading model and considering the interaction between the frozen wall and unfrozen soil under nonuniform load conditions has not been conducted [34].…”