| At present, the offshore newly sedimentary silt from sea bed is widelyused as fil ler for coa stal recla mation in Ti anjin Binhai Ne w Area. The so ftdredger soil mainly co nsists of fine grain, and has a certain structural p roper t yafter vacu u m p reloading treatme nt. Fu rther stud y on the structu ralcharacte ri st ics of so ft soil is e sse ntial becau se the spe c ial physica l propertiesand structu ral property of soft d redger soil exert a tremendous influence o nengineering design and safety.In recent d ecades, abo veground space is get ting mo re and mo re c rowd edwith increasing popu lation. Th erefore, people pay mo re atten tion to th eundergroun d space de velop ment(undergroun d rail wa y, tunnel engineering) an dhigh-rise b uildings. As excavatio n caused so il defo rmation and safety p roblemsthreaten th e safet y o f the nearb y buildings, study on structu ral-me chanicalcharacte ri st ics o f so ft dredge r soil wi th di ffe rent st re ss path po ssesses g rea tsignificance which d raws much more widesp read attentio n.In view of the proble ms, based on the previous studies, soft d redger soil o fTianjin Bin hai New Area with vac uu m p reloa ding trea t ment was cho sen fo r te stma te rial. With st ruct ural p roperty of so ft dredger so i l as the re sea rch b a si spoint, the structu ral-mechanical c haracte ri sti cs have bee n studied b y laborato rytests. The ma in conte nts and results a re a s follo ws:(1) The ph ysical p rop ertie s of th e soft dred ger so il dri lled fro m t he fieldare studied by lab orato ry tests. Th rough co mparison tests includin gone-dimen sional conso lidation tests, unconfined co mpressive stren gth tests an dconsolidation undrained triaxial tests b etween un disturbed samples andremoulded samples, structu ral-mechanical characteristics o f undisturbed soilcan be anal yzed. The results sho w that the co mp re ssion capacity an d the shea rcapacity o f undisturbed soil are sig nificantly g reater th an the remoulded soil. Inthe stress-strain curves, undistu rb ed soil befo re and after structu ral yield appearinflection point while re moulded soil don’t have. The re moulded soil appearyield as well and wit h the inc re ase o f con solidation pressu re it will be mo reobvious(2) Based o n the p ractical engineering, the tests have been carried out on the so ft d redger fill with th ree corresponding si mplified stre ss p ath includingthe axial loading of heap load state (increase pressu re), axial loading but latera lunloading state (keep constant pressu re), lateral unloading of excavatio nprocess (de crea se p re ssure), and t he advanced WF stress path triaxial apparatu sand innovative test p lan have been used. In this p aper, chan ge laws o fstructu ral-me chanical characte ri stics o f un disturbed soil with different stresspath and different deg ree o f structural da mag e have been discu ssed. The result sas follo ws:(1) St ructural yield st ress o f so ft dredger soil is not a constant valu eand it will be changed with the su rrounding e nviron ment. St ructural yield st res sis in fluenced b y cell p ressu re and stress path which are mo re than o ther fac tors.(2) In di ffe rent stre ss path, the la w o f the variation o f p ore p ressu re is not onlyrelated to surroundin g environ ment but also related to the state of structu ralyield.(3) There is an obvious deflection before and after structural yield ineffective st ress path showing the “S” shape.(4) The sh ear st rengt h of INP i sma ximu m and KCP is in the middle and DEP is mini mu m; di ffe ren t st ress pat hinfluence c ohesive fo rce mo re t han the an gle of inte rnal frictio n.(5) TheMohr’s envelope shows a broken line that the soil have not reached the state o fstructu ral yield in th e st ress pa th stage while the M ohr’s envel ope sho ws astra ight lin e that the soil have re ached the state. |
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