Qihao Yu

• Chinese Academy of Sciences

In cold regions, the frozen soil–rock mixture (FSRM) is subjected to cyclic loading coupled with freeze–thaw cycles due to seismic loading and ambient temperature changes. In this study, in order to investigate the dynamic mechanical response of FSRM, a series of cyclic cryo-triaxial tests were performed at a temperature of −10 °C on FRSM with diff...

The stability and service performance of ordinary railway subgrade are often challenged by frost heave distresses in seasonally frozen regions. This paper analysis the moisture-heat process and frost heave characteristics of the subgrade of Qinghai-Tibet Railway (QTR) using on-site monitoring data. The development mechanism of deep frost heave in o...

During the construction of cast-in-place piles in warm permafrost, the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost. Since the bearing capacity of the pile is quite small before the full freeze-back, the quick refreezing of the native soils surrounding the cast-in-plac...

The heat absorption of the railbed mainly originates from the embankment slope in permafrost regions. A novel ventilated slope (NVS) with a double‐layer convection channel is proposed and verified. By applying this method to the Qinghai–Tibet Railway (QTR), the annual average temperature at the 10 cm depth below the embankment slope surface under N...

Diurnal freeze–thaw process occurs in the Lianghekou area in winter, which will affect the construction progress and quality of the project. In this paper, the compressibility of clay experiencing the freeze–thaw (F-T) cycles under different impacting factors was investigated. A series of unidirectional F-T tests were carried out in a closed system...

Different from other geotechnical materials, the strength characteristics of saturated frozen soil have nonlinear characteristics that first increase and then reduce with the increasing confining pressure, and are sensitive to varying temperature due to the existence of ice inclusions. Based on analysis on the breakage of frozen soil, it is believe...

Investigation of resistivity has been effectively used in assessing the risks of embankmentation and failure. A two‐dimensional (2D) approximation of the surveyed object is commonly assumed for a survey line on the road surface. However, this approximation may not be met when resistivity investigations are conducted over a raised high embankment; u...

Two-phase closed thermosyphon (TPCT) is widely used to cool foundation soil and improve the stability of structures in cold regions. However, along with the cooling of soil surrounding a TPCT, frost heaving of soil can occur, which might pull the structures out, but this phenomenon has rarely been reported. In this paper, based on field observation...

Frost heave is a crucial issue of concern in seasonally frozen regions, which directly causes many engineering freezing damage problems, especially affecting the stability of embankments. To treat the frost heave diseases that occur on the embankment in seasonally frozen regions, we propose a new solar circulating heated embankment system (SCHES) b...

Frost heave has a significant influence on the stability of embankment in seasonally frozen regions, where the active heating embankment has become a new method for preventing and controlling frost heave. In this study, a field experiment was conducted based on a solar circulating heating embankment system (SCHES), and the heat collection performan...

Based on the field meteorological and ground temperature in the winter construction process of the world's third highest earth-core rockfill dam for the Lianghekou Hydropower Station (LHS) in Sichuan province, China, the daily and frequent freeze–thaw process of the filling soil in the dam and its driving factors have been studied. Observational da...

Two-phase closed thermosyphons (TPCTs) are widely used in enhancing mechanical strength of foundation soils in permafrost regions. However, engineering problems develop in embankments containing TPCTs. Based on numerical simulations, we herein discuss the influence of four important parameters, namely model size, daily variations in air and ground...

Expressways construction in warm permafrost regions is faced with serious permafrost degradation, and expressways stability is closely related to its thermal-hydro-mechanical state. However, the behaviors of moisture, heat and deformation of expressway in warm permafrost regions are not completely clear. In this study, the experimental embankment f...

Due to the complex topography and localized climate, active layer thickening and permafrost warming varied distinctly in different regions on the Qinghai-Tibet Plateau (QTP). Based on the borehole-temperature data at 93 sites from 2012 to 2018, we analyzed the temporal and spatial characteristics of active layer thickness, permafrost temperature, a...

Purpose-The purpose of this paper is to perform the thermo-hydro-mechanical (THM) numerical analysis in order to study the thawing process for frozen soil and to predict the thawing settlement. Design/methodology/approach-A new one-dimensional multi-field physical coupled model was proposed here to describe the thawing process of saturated frozen s...

The thermal effects of cast‐in‐place piles on the surrounding permafrost frequently induce deformation or failure of piles in permafrost regions. Because piles are directly inserted into the permafrost layer, the thermal disturbance of the piles is more straightforward than that of road embankments to the permafrost. Thermosyphons have proven to be...

In cold regions at high altitudes, freeze-thaw cycles due to diurnal temperature variation in the construction process in winter result in the core-wall soil materials of dams having varying mechanical properties. In this study, a series of consolidated undrained triaxial tests were performed on soil samples subjected to various numbers of freeze-t...

Winter construction in seasonally frozen soil areas is inevitable. The variation of ambient temperature causes the freeze-thaw of the filling soils and its impact is significant, and whether the countermeasures can be effectively established and adopted is particularly important for the management and control of the construction quality of the proj...

During the construction of clay core rockfill dam in cold regions in winter, the heat transfer characteristics of gravelly soil are important to the anti-freezing control of the core. Laboratory experiment and field test data showed that the frost depth of gravelly soil in unconsolidated state was deeper than that in compacted state at the early pe...

Embankment with duct-ventilated slope (EDVS) is a new kind of proactive roadbed cooling measure in permafrost regions, which is composed of multiple hollow cement ventilation ducts assembled side by side, and the ducts are laid down on embankment slope. To investigate its cooling mechanism and performance, a prototype field test was carried out on...

The embankment construction in permafrost regions changes the energy balance on the surface, resulting in the degradation of the underlying permafrost and instability in the embankment structure. Considering the strict evenness requirement for an expressway, large deformation and instability in expressway embankment cannot be allowed. Accordingly,...

Upon employing the theoretical frame of breakage mechanics for geological materials and homogenization, a new elasto-plastic constitutive model is proposed to investigate the dynamic mechanical behaviors and volumetric strain of frozen soil under cyclic loading. In this model, using a mesoscopic method to formulate the breakage of frozen soil by id...

Thermal conductivity is an important thermal parameter in engineering design in cold regions. By measuring the thermal conductivity of clay using a transient hot-wire method in the laboratory, the influential factors of the thermal conductivity of soils during the freezing process were analyzed, and a predictive model of thermal conductivity was de...

Periglacial processes can threaten the operation of engineering infrastructure. Based on field observations, the influence of four types of periglacial processes on tower foundations along the Qinghai-Tibet Engineering Corridor were investigated. These periglacial processes change the local thermal and hydraulic processes in soils around the pile f...

In permafrost regions, the construction of embankment leads to the permafrost degradation, further affecting the embankment stability. Considering wider bituminous pavement and higher technical standard for expressway than ordinary highway, the heat and deformation behaviors of the separated expressway are investigated through a full-scale field ex...

Temperature-controlled ventilated embankment (TCVE) is a feasible air-cooled embankment. It can control the heat transfer mode in ventilated duct of duct ventilated embankment according to the ambient air temperature with auto-temperature-controlled wind doors installed in the duct nozzle. For investigating the cooling performance and engineering e...

Permafrost is sensitive to both climate warming and engineering disturbance on the Qinghai–Tibet Plateau (QTP). These factors degrade the stability of infrastructure built on permafrost and reduce its service life. To counter these effects, cooling of the subgrade to lower permafrost temperature forms part of the engineering design on the QTP. Proa...

The thermal performance of an experimentally built expressway embankment with a combined cooling measure at Beiluhe Basin in the Qinghai-Tibet Plateau was investigated based on long-term field monitoring. Six-year records of soil temperatures showed that the embankment cooled by a measure combining hollow concrete bricks and ventilation ducts had a...

Existing grounded ice or floating ice in late winter represents the distinct thermal state of the lake bottom, which regulates the evolution processes of thermokarst lakes. The aim of this study was to identify either grounded ice or floating ice using ground penetrating radar (GPR) and analyze the factors that influence identification. Densely spa...

During the construction of the ±400 kV direct current power transmission line (DCPTL), frozen blocks were backfilled into the foundation pits in permafrost regions because of the lack of backfilling materials and other problems, but this resulted in less compact backfilled soils. To ensure the stability of the tower foundations, a large number of t...

The seasonal hydrological mechanisms of two thermokarst lakes on the northeastern Qinghai-Tibet Plateau (QTP) were characterized by three-year intensive field observations and a water balance model. In three ice-free seasons, the supra-permafrost discharge contributed a mean ratio of over 170% of the precipitation. In the ice-cover seasons, the sup...

The development of thermokarst lakes in permafrost regions can relate to climate change and significantly impact the hydrological regime. We investigated the configuration of permafrost and a talik under a thermokarst lake on the Qinghai–Tibet Plateau (QTP), China, using GPR, electrical resistivity tomography, drilling and ground temperature measur...

Both the inflow and outflow of supra-permafrost water to lakes play important roles in the hydrologic process of thermokarst lakes. The accompanying thermal effects on the adjacent permafrost are required for assessing their influences on the development of thermokarst lakes. For these purposes, the lake water level, temperature dynamics and supra-...

In permafrost regions with warm ice-rich frozen soil, the changes in backfill soil of the cast-in-place bulb pile and the precast footing are studied over 2 years. The study results show that the freezing period is longer, but the thawing period is shorter for the backfill soil compared with those at the natural control sites. Depths of permafrost...

Structural damages due to frost jacking of a foundation depend on the adfreeze bond between the freezing soil and the structure. To reduce the adfreeze bond strength between the foundation surface and the frozen ground, a fiberglass reinforced plastic (FRP) cover was proposed for foundations along the Qinghai-Tibetan transmission line. Direct shear...

Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost. The common assumption is that this conductivity is considerably lower in the thawed than in the frozen state, λt/λf < 1. Using a 9-year dataset from the Qinghai–Tibet Plateau (QTP) in conjunction with the GEOtop model, we...

Lakes/ponds in permafrost regions may have strong thermal influences on the foundation of adjacent infrastructures such as railways, highways, and transmission lines. To assess the thermal influences of lakes on the stability of tower foundations along the Qinghai-Tibet Power Transmission Line (QTPTL), field works were conducted during mid- to late...

Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost. The common assumption is that this conductivity is considerably smaller in the thawed than in the frozen state, λt/λf < 1. Using a 9-year dataset from the Qinghai-Tibet Plateau (QTP) in conjunction with the GEOtop model,...

The stability of tower foundations in permafrost regions is related to the thermal regime of the adjacent soils. The aim of this study is to investigate the ground temperature evolution in the foundation backfill of a tower, which is constructed by open excavation on the Qinghai–Tibet Plateau. Soil temperature and water content in the backfill were...

The Qinghai-Tibet Power Transmission Line (QTPTL), crossing about 550 km permafrost regions, was constructed between July 2010 and October 2011. Based on 4 years field observations since the construction, thermal and displacement performances of tower foundations in permafrost regions along the QTPTL were analyzed. The observational results from 10...

A transmission tower foundation embedded in frozen soil is subject to both the wind-induced uplift and frost heave forces. The frost heave results in an upward force acting on the foundation, while additional stress induced by the structure load may compress the underlying soils. The freezing- and thawing-induced deformations tend to cause further...

Two-phase closed thermosyphons are extensively used for cooling foundation soils of tower footings in permafrost regions along the Qinghai-Tibet Power Transmission Line (QTPTL). In this paper, the working period of these thermosyphons is firstly determined by field observations. Then, a 3-D numerical heat transfer model is constructed to study the...

The Qinghai-Tibet Power Transmission Line (QTPTL), a project of the ± 400 kV direct current (DC) grid system from Golmud in Qinghai Province to Lhasa in Tibet Autonomous Region, China, was recently built to meet the power transmission needs. On the Qinghai-Tibet Plateau (QTP), it is another milestone engineering project since the completion of the...

Generally, construction for pile foundation in permafrost has to be carried out in winter to minimize the thermal distribution to the underlying or surrounding permafrost. Thus, there exists a problem that it is hard to meet the stipulated requirement to the compaction degree of the backfilled frozen soil blocks around the pile foundation excavated...

Subsurface moisture content is one of the critical factors that control the thermal dynamics of embankments. However, information on the subsurface moisture movement and distribution in embankments is still limited. To better understand the coupled water and heat transport within embankments, subsurface temperature and moisture of an asphalt paveme...

Construction of power transmission lines is becoming an important part of permafrost engineering in China. This paper reviews the construction status and problems of transmission lines in different countries, as well as corresponding solutions that would be of practical significance for sustainable engineering practices. Russia has the longest hist...

Climate warming has been observed for some time in the permafrost regions on the Qinghai-Tibet Plateau (QTP), China, resulting in active layer thickening, shrinkage or expansion of thermokarst lakes, and reduced permafrost extent. Little is known, however, about the hydrological processes near thermokarst lakes and their influences on lake developm...

The active layer in permafrost regions plays an important role in energy exchange between permafrost and atmosphere. Rainfall is one of the dominant factors affecting thermal-moisture dynamics of the active layer. To better understand the thermal-moisture dynamics and the interaction between rainfall and the active layer in-detail, in situ experime...

The Qinghai-Tibetan ±400 kV direct current grid interconnection project runs across 1038 km of permafrost and seasonally frozen-ground in the interior of the Qinghai-Tibetan Plateau. The mean annual air temperature of the Qinghai-Tibetan Plateau varies between -3 C and -7 C and the minimum air temperature is lower than -37 C in short durations. The...

As one part of the National Highway Network Planning in China, the Qinghai-Tibet Expressway (QTE) from Golmud to Lhasa will be built in the interior of the Qinghai-Tibet Plateau (QTP) across about 630 km of permafrost lands. Due to the problematic interactions between the engineering foundations and permafrost, the frozen-soil roadbed of the QTE wi...

The Qinghai–Tibet Highway and Railway (the Corridor) across the Qinghai–Tibet Plateau traverses 670 km of permafrost and seasonally frozen-ground in the interior of the Plateau, which is sensitive to climatic and anthropogenic environmental changes. The frozen-ground conditions for engineering geology along the Corridor is complicated by the variab...

Shading boards (SB) were tested on an embankment slope as one of the measures for actively cooling permafrost in roadbed engineering along the Qinghai-Tibet Highway on the Tibet Plateau, China. A series of tests, evaluating the cooling mechanism of SBs, also were conducted in the laboratory that showed that the SB cooled the permafrost by significa...

Ground-penetrating radar is a fast noninvasive technique that can monitor subsurface structure and water-content distribution. To interpret traveltime information from single common-offset measurements, additional assumptions, such as constant permittivity, usually are required. We present a fast ground-penetrating-radar measurement technique using...

Permafrost in the Da and Xiao Xing'anling Mountains in northeastern China is warm, thin and sensitive to climatic warming. In the 1970s, the southern limit of permafrost (SLP) was empirically correlated to the −1 to 0°C isotherms of mean annual air temperature (MAAT) in the western part of the Da Xing'anling Mountains, to about 0°C in the northern...

A temperature controlled ventilated embankment (TCVE) of roads or railroads is proposed as an attractive engineering approach in permafrost regions. Comparing the measuring results in ventilated embankment (VE) with same conditions, which nearby TCVE testing fields, we demonstrate that in two testing fields with 30-cm and 40-cm diameter controlled...

Auto-temperature-controlled ventilation embankment is an effective engineering measure for “cooling roadbed”. Practice proves that this new method can sufficiently make use of natural cold energy. It has the advantages of higher efficiency, better cooling effect and feasibility in engineering practice, and wider application in various environment,...

Based on observed data from field-testing embankment of the Qinghai-Tibet Railway, ground-temperature controlling effect of duct-ventilated embankment is studied in this paper. The results show that ventilation ducts can effectively cool the soils surrounding the ducts of the embankment, and the heat budget of the ambient soils in a year shows as h...