Abstract
Granite residual soil is one of the most frequently encountered problem soils in tropical regions, whose mechanical behavior heavily depends on the pattern of variation of mean effective stress (p’) during shearing, which can be classified into three categories: increasing-p’, constant-p’, and decreasing-p’. Unfortunately, so far, the stress–strain strength characteristics of granite residual soils have been studied mainly under increasing-p’ stress paths, although it is very likely to encounter stress paths with decreasing p’ in practice, especially in excavation engineering. Moreover, most pertinent research has focused on remolded granite residual soils, whereas undisturbed specimens have not yet received enough attention. In this paper, stress path triaxial tests considering different patterns of variation of mean effective stress were conducted on an undisturbed granite residual soil. Subsequently, a variable termed loading angle was introduced to quantitatively represent stress path. The influences of stress path on the Mohr–Coulomb strength parameters, deformation characteristics, ductility, and shearing stiffness were analyzed, with an emphasis on the role of pattern of variation of mean effective stress. The experimental results show that friction angle of the soil increases while cohesion decreases with the increase in loading angle. The increase in loading angle leads to less volume contraction and smaller failure strain. During shearing, the soil exhibited a less brittle response under stress paths with smaller loading angles. The initial secant shear modulus first decreased and then increased as the loading angle increased, with the minimum shearing stiffness occurring at a certain loading angle lying between 90° and 123.7°.
Highlights
As the product of the weathering of parent rocks, granite residual soils are widely distributed in the tropics and subtropics, including some developed regions such as Singapore, Hong Kong, and the southeast coastal areas of China [1,2,3]
In the context of excavation engineering, this paper aimed to study the effects of patterns of variation of mean effective stress on the mechanical behavior of undisturbed granite residual soils (UGRSs), with attention focused on decreasing-p’ stress paths
The peak shearing strength mobilized in the drained test is higher than that in the undrained test under the same confining pressure due to a higher level of mean effective stress
Summary
As the product of the weathering of parent rocks, granite residual soils are widely distributed in the tropics and subtropics, including some developed regions such as Singapore, Hong Kong, and the southeast coastal areas of China [1,2,3]. Many aspects of granite residual soils have been studied, including the engineering geological characteristics [2,9], index properties [10,11], mechanical properties [8,12,13,14], heterogeneity [15,16,17,18] (soil properties vary vertically and horizontally due to the variable degree of weathering), small strain stiffness [19,20], unsaturated soil behavior [21,22,23,24,25], and the in situ measurement of soil. Istoiisl weliedmeleynktsnionwdniftfhearet ndtuprionsgitieoxncsavoafttiohne ofofuanfdoautniodnatpioitn apreitq, ustirteesdsipffaetrhesnte[x3p6e],riaesnscheodwbnyisnoFiligeulerme 1e.nDtsififnerdeinfftefrreonmt pthoesisttiroensss poaf tthheoffocounnvdeantitoionnpalit ttsfsaroitatsftrdirhroeitrraneritereeaxseasioxsnqsisisoansoiiiugfpladliipinatllestethaetegltteehtroeeslhdumsetssfpstsitcmtwrfseitwhfu(tuneeci(ecirtecrtonttheseopxhuntnsspnidirsndtteaesteie[easntrntc3acxnhirad6erntpeteneh]ntate,aσdbechsraσs3eoiiesitb3nenthadoptsngangeohetrcndσtmcσpeoeodr3dw3rim.edaeniiaIancndentc.nstcdirciiiidcrIoensnrtteceangicoaoFioaso-sbsnioinspngnivisof’nsnuogtibdtsgoagrfatvee-nσurdnpiσfe1ts1otoe’)1sσ.,ftuσrs)soh1mDs,t1s,rrpao,swiemattiowfahslfthbtiaesiahlheooitrtplliesienteleo.lbhanemenσfTtotσmosh3hetffo3rshrorneeieo.rarlnrtemsmTseeatfomfhsolaiiofetnluaeioihmrnnirenueentesle,dhntsefscnhpoedamtcotrertraosnesieietonosis,siindinsnosrtpdtaetnpstraptenohianopiiotonttefttirh,afthabpn,tttpenohhootidhtfideetdtsttσecshoemσboe1mseem1onxdeixgtddpveceptancheeeecoenhcnrsramoreridiatneigefaineionatnascrnihnscenceacoeeeaas-ldesfll bbeehhaavvioiorroof fssooililuunnddeerrddeeccrreeaassiningg-p-p’ ’sstrtreessssppaatthhssmmuussttbbeessuuffffiicciieennttllyyssttuuddiieedd[[3377]]
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