In order to study the influence of the backfill characteristics of the large karst area on the load transfer of the pile foundation and to improve the safety and economy, considering the characteristics of the side friction resistance of the pile back and the pile in the large karst area, based on the exponential load transfer function, the method for calculating the load-settlement curves of backfill piles in large karst area is obtained. The method is verified by the existing research results and engineering examples. The results show that the proposed method is in good agreement with the actual project. Based on this method, the influence of parameters on the load- settlement curves of karst piles is analyzed. The results show that the load-settlement curves of pile foundation increase with the axial strain, particle size of gravel and pile parameter ?b, and the ultimate bearing capacity of the piles increases with the increase of the axial strain and pile parameter ?s and decreases with the increase of the particle size of gravel.

那丘隧道为长隧道,位于湖南省永吉高速第4合同段.左线K12+ 060～K14+ 935,长2 875 m,右线K12 +060～YK14 +920,长2 860 m.左线主洞掌子面施工至K14 +513处,发现本次K14+ 350～520段大型溶洞,是一廊道厅堂式大型岩溶.从回填、改桥及改线及施工难度等角度对此岩溶的处治技术进行了研究,力求为工程及技术支持,并为类似工程提供参考.

Collapse occurs normally during tunnel construction in poor geology.Yangdontan II tunnel exists in Huaitong Expressway ,entrance section is buried in shallow layer,and its surrounding rockmass is weathered sand-slate,a,it is the most difficult tunnel to be build in the world.With the fuzzy-hierarchy assessment model,Evaluation of collapse disater during a underground-water tunnel con-struction is made,which is the shallow and pre-pressure tunnel,and its disater degree is gained.The risk control measure are put forward,the result will provide guidance to construction.

Sandy slate is distributed widely in Huai-Tong Expressway.Under the action of water, sandy slate tends to disintegration and softening,then appears strength reduction.For researching the fully,strong,moderately and weak weathered sandy slates in slopes belonging No.24 section of Huai-Tong Expressway,the disintegration character test,softening test,unconfined compression test and shear permeability test were carried out,which revealed the hydrological characteristics to sandy slates.Re-search shows that:①sandy slate with strong disintegration characteristics.Sandy slate exposed in water, oxidation reaction occurs rapidly,and then collapse.The higher degree weathered,the disintegrating is stronger;②the hydrological characteristics of sandy slate are ranked as:weak weathered <moderately weathered <strong weathered <fully weathered;③sandy slate is drier,disintegrating effect is more obvi-ous,the sudden rain after long drought will lead to strong disintegrating and induce landslide easily.

Yang Dong Tan No.2 tunnel is for two hole one-way traffic tunnels.The tunnel collapse happen during its construction.By using the numerical analysis technology,combined with numerical simulation,the simulation analysis of mechanical effect of tunnel collapse rescue is made in this paper. Later the positive hole beach No.2 tunnel right hole YK194 +040 -YK194 +085 segment processing scheme is formed .It will provide the technical support for the construction safety of tunnel.

分析了怀通高速22合同段的磨石隧道怀化端左、右洞二衬局部地段出现裂缝的原因,并研究了相应的处治技术,为隧道病害的有效治理提供了技术支持.

Combined with a case,the construction of tunnel gate and tunnel body in III and IV grade part are numerical simulated in this paper,the analysis results will provide some useful technical reference for pre-support and structure stability analysis.

Combined with a real case,and with theoretical and numerical simulation,surface settlement caused by excaving in shallow layer tunnel is inferred in this paper.the analysis results will provide some useful technical reference for surface settlement control.