Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-cond...Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-conditioned clay soils were investigated,with their potential use as an alternative means to assess foam optimization being examined.A series of laboratory and fieldtests was conducted,including vacuum dewatering tests that considered the effects of filtrationtime and pressure,vane shear tests,and improved cone pullout tests under different gravimetric water content(w)and foam injection ratio(FIR)conditions.It was found that the filtrate loss(FL),which characterizes dewaterability,was increased by extended vacuum filtrationtime and elevated pressure.While increases in w and FIR enhanced FL,reductions were observed in the undrained shear strength(cu),tangential adhesion stress(Fs),and normal adhesion stress(Fn).Furthermore,a linear decrease in FL with increasing mechanical indices(cu,Fs,and Fn)was demonstrated by both laboratory and fielddata fittingresults,regardless of w,FIR,and dewatering conditions.This study provides novel insights into the understanding of vacuum dewatering mechanisms in foam-conditioned clay soils,while a simple approach is proposed for evaluating foam conditioning effectiveness in EPB shield tunneling applications.展开更多
To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coast...To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.展开更多
基金supported by the National Youth Top-notch Talent Support Program of China(Grant No.00389335)the National Natural Science Foundation of China(Grant No.52378392)the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province(Grant No.00387088).
文摘Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-conditioned clay soils were investigated,with their potential use as an alternative means to assess foam optimization being examined.A series of laboratory and fieldtests was conducted,including vacuum dewatering tests that considered the effects of filtrationtime and pressure,vane shear tests,and improved cone pullout tests under different gravimetric water content(w)and foam injection ratio(FIR)conditions.It was found that the filtrate loss(FL),which characterizes dewaterability,was increased by extended vacuum filtrationtime and elevated pressure.While increases in w and FIR enhanced FL,reductions were observed in the undrained shear strength(cu),tangential adhesion stress(Fs),and normal adhesion stress(Fn).Furthermore,a linear decrease in FL with increasing mechanical indices(cu,Fs,and Fn)was demonstrated by both laboratory and fielddata fittingresults,regardless of w,FIR,and dewatering conditions.This study provides novel insights into the understanding of vacuum dewatering mechanisms in foam-conditioned clay soils,while a simple approach is proposed for evaluating foam conditioning effectiveness in EPB shield tunneling applications.
基金supported by the National Natural Science Foundation of China(Nos.51878648,52070184)the National Key Research and Development Program of China(No.2019YFD1100100)。
文摘To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.
