毕业设计外文翻译(6)

92 Van hung DAO．Wa r Science and Engineering。Sep．2009，Vo1．2，No．3，87-95

Plastic region radius(m) 9．5 9．O 8．5 8．0 7．5 7．0 6．5 6．0 5．5 5．0

Elastic region radius(Il1)

Fig．5 Rock stress within plastic region Fig．6 Rock stress within elastic region

Displacement“r(m)

Fig．7 Stress release coefficient of tunnel boundary Fig．8 Interactive curve between ground base and

without support along tunnel axis supporting structures for diferent initial displacements

Based on the Fenner-Pacher theory and The Vietnamese Construction Design Standard

厂Dr Underground Works(Ministry of Construction 2003)，we compared the pressure on the

supporting structures with the m aximum pressure value that the supporting structures are able

to bear(which is equal to the stress at the elasto—plastic boundary O're)to analyze the above

results．It con be concluded that：

Supporting structures installed when the initial displacement Uo：0．083 m result in the

following： There iS imm ediate consolidation after the tunnel excavation． Pressure on

supporting structures ei=6．902 M Pa> =4．019 5 MPa．W ith unfavorable operation of

supporting structures，the rock continues deforming after the support is in place．This results in

local instability．

Supporting structures installed when the initial displacement Uo：0．087 m result in the

following：Consolidation occurs at a distance of =1．O05ri= 1．708 5 m．and the stress release

coefi cient =0．481 7．Pressure on the supporting structure =3．781 8 M Pa < =

4．0 1 9 5 MPa．The rock has suficient deformation，and the tunnel is stable．

Supporting structures installed when the initial displacement Uo：0．093 m result in the

Van-hung DAO．Water Science and Engineering,Sep．2009，Vo1．2，No．3，87-95 93

一∞邕 一0= > ∞2Is 言dl乏 ； 》 h

言白 ) 2；∞∞ 口 0焉pIIo兽0u

following：Consolidation occurs at a distance of x=2．2，：=3．74 m．and the stress release

coefi cient =O．732 7．Pressure on the supporting structmcture =1．95 1 1 M Pa 《 =

4．019 5 MPa．The rock has major deformation，indicating that the tunnel can be unstable．

Supporting structures installed when the initial displacement u0=O．097 m result in the

following：Consolidation occurs at a distance of x=4 ：6．8 m，and the stress release

coefi cient =0．868．Pressure on the supporting structmcture =0．963 2 MPa 《 =

4．019 5 M Pa．Rock deformation is too great；there can be rock loosening of the tunnel roof

causing the increase of rock pressure．The tunnel is unstable． Th us，in this case，we can say that at each time，with a certain displacement u0 ranging

from 0．086 5 m to 0．09 1 9 m．we can install supporting structures that satisfy the stability and

economical requirements． 4 Conclusions

In general，the determination of initial displacement“o described in this study is more

accurate and detailed than assumptions of the initial displacement value蹦0(Vu and Do 2007)．

Values of u0 depend on the stress release effect and，when compared，provide a more

complete solution than the solution with curves that exclude the stress release effect(Hoek and

Brown 1980；Wiliams 1997)．

The survey described above has shown that the convergence—confinement method is an

efective design tool for obtaining appropriate supporting time．It

is completely different from

the traditional tunnel design method，which applies the early consolidation and quickly lining

installation rules，considers the supporting structures provisional supporting structures to bear

loads of loosened rock，and ignores the load—bearing capacity of rock masses．

However,the problem is limited to the two—dimensional elasto—plastic model，hydro—static

inital stress field and circular tunnel cross—section．Therefore．in the case of rock with a

non—hydrostatic stress field，or of non—circular tunnel cross—sections，the destructive models

such as the non．homogeneous elasto—plastic，visco—elastic，and brittle models，need to be

studied so that the convergence—confinement method can be applied more widely in tunnel design．

References

Anagnostou，G，and Kovari，K．1993．Significant parameters in elastoplastic analysis of underground openings．

JournalofGeoteehnicalEngineering，l19(3)，401-419．[doi：10．1061／(ASCE)0733—9410(1993)119：3(401)】

Brady,B．H．G，and Brown，E． 2004．Rock Mechanicsfor Underground Mining．Dordrecht：Kluwer Academic

Publishers．

Carranza Torres，C．，and Fairhurst，C．1999．The elasto—plastic response of underground excavafions in rock …… 此处隐藏：2326字，全部文档内容请下载后查看。喜欢就下载吧 ……