Infiltration Law of Water in Undisturbed Loess and Backfill

Abstract

Loess has the characteristics of complex structure and reduced mechanical strength after encountering water. In Chinese loess areas, irrigation, water storage, and rainfall affect the stability of the original loess structure and cause damage to the foundation. This paper analyzes the results of in situ water immersion test (in order to study the permeability of water storage in undisturbed loess), rainfall test (in order to study the permeability of rainwater in the backfill loess), and water storage test (in order to study the permeability characteristics of water storage in backfill loess) on the filling site and studies the permeability law of water in unsaturated layered loess and backfill remolded loess. The results of the in situ immersion test show that the vertical seepage velocity of water was very fast, and the infiltration depth was close to 25 m after 9 days of water storage, and at the interface of the new loess, the paleosol, and the old loess, the water infiltration line appeared to be refracted. Finally, the vertical and horizontal penetrations of water in the loess are analyzed, and the range of water immersion and saturation are determined. Through the rain test and water storage test of a loess-filled surface, the relationship between the moisture content and depth of the backfill loess before and after rainfall and storage is obtained. The results of rain period test show that the water infiltrated into the loess about 3 m after 25 days of rainfall. A further 90 days storage test shows that the final infiltration depth of water was about 7 m.

A New Method for Reducing Collapsibility of Loess Foundation with Thicker Deposit: The Borehole Preimmersion Method

“…From equations (14) and (15), the calculation formula for the soaked loess immersed through four rectangular water injection holes is expressed as follows:…”

“…An et al [14] studied the settlement characteristics of loess by conducting a field immersion test on collapsible loess with water injection holes. Meng et al [15] studied the permeability law of water in unsaturated layered loess and backfill remolded loess by the in situ water immersion test, rainfall test, and water storage test.…”

Study on the Loess Immersion Test of Metro Line 2 in Xi’an, Shaanxi Province, China

“…At present, there are two methods to study loess collapsibility: one is the combination of indoor test and mathematical method, and the other is the field water immersion test. e former is mainly to study the mechanism and mathematical model of loess subsidence [7][8][9][10][11], while the latter can intuitively get the test site after immersion subsidence development process and water migration process in space [12][13][14][15][16][17], and then the site of the subsidence level to make evaluation [18][19][20][21][22][23], and this method is more recognized by the engineering practice. Xing and Liu [24] analyzed the influencing factors of negative skin friction for pile foundations in collapsible loess regions through water immersion tests, and the main factors are cumulative relative collapse amount, pile type, and change in loess collapsibility.…”