Engineering and Structural Geology Evaluation of Khansar-Boien Miyandasht Tunnel

Ghazaleh Edrisi M.Sc. Structural Geology and Tectonics The University of Damghan, Semnan, e-mail: [email protected]

Rassoul Ajalloeian Associate Professor The University of , Isfahan, Iran e-mail: [email protected]

ABSTRACT Lack of geological and tectonical knowledge in a region causes hazard in project implementation. There are many examples related to this issue in Iran and the world. Main purpose of this research is to analyze the fractures because of their importance and effect on the implementation of engineering and civil engineering projects such as Khansar-Boien Miyandasht tunnel. For this purpose, the process and density of the fractures and their spatial-geometric position were investigated. Therefore, joints and faults in the Khansar syncline area and the site of Khansar–Boien Miyandasht tunnel were collected, then processed by interpreted in the software such as Stereo32 and Georient. According to the result, a group of joints can be related to pre-tectonics, another one can be related to syn-tectonics(folding and faulting) and some fractures are related to the post-tectonics. Geomechanically, syn-tectonic fractures are extensive in depth and these issues are very important, so it should be considered in implementing the project of Khansar tunnel. Results of the geological engineering study such as, uniaxial strength test, point loading, Schmidt hammer, and ultra-sonic Test were showed high-resistance massive orbitolina limestone , and alternation of shale , limestone , medium- resistance limestone and black slates include low resistance that lead to apply the supports with higher safety factor. Considering the tunnel direction (NNE-SSW), high slope fractures and tunnel tensions, it is possible to create sliding wedges in the left wall and left ceiling of the tunnel. Therefore, tunnel drilling should be performed cautiously by blasting method. KEYWORDS: Faults, Joints, Tunnel, Syn-tectonic, Post-tectonic, Slope, Sliding wedges, Geological Engineering,

INTRODUCTION Khansar-Boien Miyandasht area is located at 160 km northwest of Isfahan. This area has been exposed to severe deformation because it is located in The Sanandaj-Sirjan zone. This zone has different names [20, 12, 10, 21, 8, 23]. Falken[10], Brou and Riko[8], Hinz and McQuillan[7], Farhoodi[8]and Alavi[9] Were considered the zone as a subzone of the Zagros orogeny due to structural trend conformity, structural pattern uniformity, thrust dominance especially the acceptance of standard pattern of orogenic regions in concurrence zones. Mohajjel and Sahandi[15] believed the Sanandaj-Sirjan zone consists of large scale composite duplex structures with oriental northern slope that cause tens or hundreds kilometers displacement of sheets from phanerozoic rocks units[1]. According to Mohajel et al. [16, 17], internal Sanandaj–Sirjan zone has completely been deformed

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Vol. 20 [2015], Bund. 7 1752 and it includes passive marginal sequence of Paleozoic–Mesozoic in which Khansar is located. According to Nabavi[18], fractures systems and faults that are attributed to Simrian and Katangaie orogenic movements are like central Iran and they cut Zagros orientation. In terms of tectonics, this zone consists of large- scale composite duplex structures or over thrusts whose trusts slope is toward oriental north. These successive thrusts lead to a complete stratigraphy sequence of different formations can't be found in Sanandaj–Sirjan zone and most contacts, faults and rocks are discrete and crushed (Figure 1).

Figure 1: Continues on the next page. Vol. 20 [2015], Bund. 7 1753

Figure 1: Generalized structural and tectonic map of Iran (adapted from Stöcklin, 1968[22] and Berberian, 1981[5]). Study area has been shown with yellow color lines.

Structural Geology Geological history of the study are related to map1/100000 Golpaiegan. This has been prepared by Mohajel and Eftekharnejad[14]. Nadimi and Konon[19] have studied strike–slip faults in the central part of Sanandaj–Sirjan zone in Zagros orogenic belt and active terminals of this faults in Zayandehrood river displacement. As total orientation of Sanandaj–Sirjan zone shows, the study area has many faults and fractures and folds which are in the same orientation as Sanandaj–Sirjan zone. The mountainous region along the Khansar-Boien Miyandasht road is considered as a syncline axis and the Major faults of the regions, are approximately stretched in the same orientation. These faults have Reverse and strike-slip components of movements. These findings reveal that the orientation of exerting forces were initially NE-SW. After that, these structures have become folded again because of exerting forces with other orientations. Therefore, recumbent and inclined synclines have been made in some parts. A group of the fractures are almost N–S; and another group follows Zagros trend and has NW-SE trend. The area of the fractures in this region has NE-SW trend, almost perpendicular to Zagros direction, because this region is under pressure of Arabic platform. Another group of the fractures follow Zagros trend. A group of the faults and the joints do not follow mentioned trends and they are affected by significant folding in the region.

Lithology of the tunnel direction

Firstly, there is unit K1 or limestone. This unit is thick in the study area and it is as a mass in some place. It seems that it has good compressive strength. However, because this unit is from limestone, karstic and soluble cavities should be evaluated carefully in order to reduce the possible problems during drilling. A main point about this unit is that it has shale inter layers in the study area; and it Vol. 20 [2015], Bund. 7 1754 causes problems in drilling direction. Shales with active clay are expanded when they become wet. In addition, during drilling and removing tension, they become expanded and cause joints, fractures and fissures. In some cases, shale layers do not allow ground water to pass because of their impermeability and therefore when they are removed, groundwater, existing water in karstic cavities, leaks into the tunnel and it becomes problematic. Thus, careful investigation of these layers and geo- mechanical characteristics are necessary. Second unit is Ksh-l. It includes limestone shales with inter layers from thick layer limestone. The third unit is Kdo or buff- colored sand dolomite and final unit belongs to older rocks, i.e. black slates and Jurassic serzite schists.

Dynamic analysis of the study area In dynamic analysis of an area with specific tectonic conditions, two parameters play main roles including: 1) Main tesnsion direction 2) Ellipcity and ellipsoid orientation of the tension [18].Figure 2, shows the position of the normal and inverse faults and geometrical lineation, maximum and minimum main strains orientations on the structural map 1/40000 prepared from Geological map of 1/100000. Existing tensions of region based on the progressive geometry show the fractures of the under study region that follow specific geometry of shearing zone. A group of these fractures follows Zagros trend (west north-East south) such as Dalan and Khansar faults that act as dextral inverse; another group has northern-southern trend. They are fractures R'(dark green) with position 322/50 that act in opposite orientation of dextral shear, i.e. sinistral shear. Third group includes fractures in shear direction with a difference of φ/2 from fractures R' , which are called fractures R(yellow) and is located in 275/60. The fourth group, which are compressive fractures includes fractures P (blue) which is located in 355/36. The final group includes fractures T (black) which is located in 62/78 (which shows tensile fractures). Faults and joints represent these fractures.

Figure 2: Position of the faults and lineation on map 1/100000 Golpaiegan (parallelogram shows strain and arrows show maximum and minimum main strain orientation). Vol. 20 [2015], Bund. 7 1755

General pattern of the joints orientations In the field studies about 994 joints were collected. These joints were analysed by in the software stereo32. Figure (3a, b) shows the total characteristics of the collected joints as contour diagram and distributions of the joints show three high frequency points. The highest orientation belongs to NE (figure 3a). These joints indicate high to medium dips and are perpendicular to bedding (layering) or they are oblique. The second orientation is related to SE which has high dips. The third orientation is related to NW and these joints have the high dips too. Rosette diagram related to joints in part indicates the joints frequency based on dip direction. The dip direction 225, 290, 210 and 310 are high, respectively. Therefore, it is concluded that direction 30 to 35, direction 20 to 25 and direction 310 to 320 indicate first, second and third frequencies, respectively.

a b

c d

e f

Figure 3: Continues on the next page.

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g h Figure 3: General pattern of all joints orientations a, b; in Jurassic lithology c , d; in lower Cretaceous lithology, e, f; in upper Cretaceous lithology, g, h

Orientation pattern of the joints in Jurassic lithology indicates (c, Contour diagram), dominant direction of NW-SE that has medium dip. Part d shows rosette diagram based on dip direction that is dominant orientation N20E. Because Jurassic layers are from black slates, there are many crushing. Figure 3e shows contour diagram based on dip direction of the joints from lower Cretaceous rocks. Joints frequency has been shown in three regions on contour diagram. The most frequency is related to dip direction 115 to 120. These joints have high dip. Second frequency is related to dip direction 300 and last frequency belongs to dip direction 35. Rosette diagram shows four frequencies in dip direction NW and SW. Figure 3 g, h shows contour diagram and rosette diagram based on dip direction of joints from upper Cretaceous rocks. As contour diagram shows the poles of these joints has higher density in three regions. It shows first frequency N35E, second frequency S60E and third frequency N60W. Rosette diagram shows the most frequency 210 based on dip direction. Most of these joints have high dip. In lower cretaceous, in rosette diagram, the frequency of the dip direction of joints show direction NW while in upper cretaceous the frequency of the dip direction of joints shows direction SW. Therefore, we conclude that most joints with dip direction NW have formed in lower cretaceous and most joints with dip direction SW have formed in upper cretaceous. Therefore, they show two different tension orientations.

Joints, orientations relative to the tunnel direction Because tunnel direction is NNE-SSW, in general analysis of the joints, the joint group with the most frequency in orientation NE is perpendicular to the tunnel direction and the other two groups (SE, NW) are relatively oblique to the tunnel direction. These two groups have relatively high dip about 75°-90°. Joints from Jurassic rocks are almost perpendicular to the tunnel direction and their dip is about 50°-70°. Joints from lower cretaceous rocks have three main directions relative to the tunnel direction. First and most frequency are related to NE_SW direction with the dominant dip direction of NW. This group of the joints has the highest dip and is relatively oblique to the tunnel orientation. Second group of the joints is belonged to NW-SE direction with SW dip direction. This group is almost perpendicular to the tunnel direction and its dip is about 35°-65°. Third group of these joints has NE-SW direction with the dominant dip direction of SE. This group of the joints is oblique relative to the tunnel orientation and their dips are high (70°-90°). Joints from upper cretaceous rocks show the most density of the joints belongs to NW-SE direction with dominant dip direction of SW. These joints are almost perpendicular to the tunnel direction and their dips are about 35°-65°. Vol. 20 [2015], Bund. 7 1757

Mechanical behavior of the rocks of the tunnel direction As it is known, joints are very important in engineering geology. For example, rocky blocks have formed because of joints intersection. After drilling, underground structures may become loose and if they do not become safe by supporting systems, they will collapse into the underground space. Bieniawski [6] considered joints, layering surfaces and faults as effective factors on the rock resistance. The role of the fractures is clear in popular classifications such as RQD[9], Q[3], RMR[7], and GSI[4] for rock masses. Four tests were performed including ultrasonic, uniaxial strength; point loading and Schmidt hammer in order to achieve the rocks classification. The results of the mentioned tests are shown in table 1. Classification was performed with the mentioned methods and results are shown in tables 2, 3, 4 and 5.

Table 1: Geo-mechanical tests results sample Schmidt hammer point loading uniaxial resistance Ultrasonic MPa MPa MPa m/s 1 46 2/76 - 3785/7 2 47/2 - 50/3 6111/2 3 46/9 - 22 5467/6 4 36/7 6/19 - 3489/5 5 43/3 4 29/7 5988/3 6 29/1 4/53 70/7 6803/6 7 38/9 6/12 - 5670/3 8 22/1 2/18 45/8 5989/5

Table 2: Boreholes positions and rock qualities Borehole ID position lithology Borehole RQD Quality of rock mass depth BH3 Outlet Orbitolina limestone 130-136 57/4 Medium mouth BH3 Outlet Fault ferrous dolomite 136-142 46/4 Loose mouth BH3 Outlet Massive layer thick limestone 118-124 87/75 Very good mouth BH4 Outlet Massive layer thick limestone 60-65 100 Very good mouth BH4 Outlet Black slate 75-80 19/5 Very loose mouth Average - 62/21

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Table 3: RMR classification for 5 samples in outlet region of the tunnel Lithology UCS RQD aperture Discontinuity Water Discontinuity RMR RMR conditions conditions orientation Numr Description Ferrous 7 13 10 20 15 -5 60 Almost dolomite good Ferrous 2 13 10 20 15 -5 55 good dolomite Ferrous 4 13 10 20 15 -5 57 Almost dolomite good Thick layer 7 13 10 20 15 -5 65 Almost limestone good Orbitolina 4 13 10 20 15 -5 57 Almost limestone good

Table 4: Q classifications for 7 stations near the tunnel station RQD Jn Jr Ja Jw SRF Q Numb Q Description Jurassic blak slate 50 12 3 8 1 1 1/56 Weak Orbitolina limestone 50 9 3 4 1 1 4/16 Almost good Alternation of shale and limestone 50 6 3 8 1 1 3/13 Weak Alternation of shale and limestone 50 15 3 3 1 1 3/33 Weak Ferrous Dolomite 50 6 3 4 1 1 6/2 Almost good Thick layer massive limestone 50 3 3 6 1 1 8 Almost good Ferrous Dolomite 50 3 3 4 1 1 6/2 Almost good

Table 5: Rock mass classification with four methods in limestone Classification Q RQD RMR GSI system average 4/7 50 59 45

Regarding the tunnel stability, support system and stand up time estimations have been shown in table 6 based on Q, RMR and RQD. Table 7 shows the determination of support system based on RQD and RMR for existing lithologies in the tunnel direction.

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Table 6: Suggested support systems of the tunnel based on RQD in different lithology Lithology Drilling RQD Support system Support system Support system method Steel frame Rock bolt shotcrete Orbitolina Mechanized 57/5 Light to medium frame with Networking 5-6 2-4 inches in crest Limestone spacing 5-6 rock load(0.4-1)B foots Orbitolina blasting 57/5 Light to medium frame with Networking 3-5 4 inches or more in roof Limestone spacing 3-4 rock load(0.6- foots and walls 1/3)B Ferrous Mechanized 46/4 Medium to heavy circular Networking 3-5 4-6 inches in roof and Dolomite frame with spacing 3-4 foots foots walls with meshing rock load (1-1.6)B Ferrous blasting 46/4 Medium to heavy circular Networking 2-4 6 inches in roof and Dolomite frame with spacing 2-4 foots foots walls with medium rock load (1.3-2)B meshing Thick layer Mechanized 88 Light frame with spacing 5-6 * Networking5-6 the thickness of 2-3 limestone rock load(0-0.4)B foots in center inches and in crest2-4 inches* Thick layer blasting 88 Light frame with spacing 5-6 Networking 5-6 the thickness of 2-3 limestone rock load(0.3-0.6)B* foots in center* inches and in crest2-4 inches* Black Mechanized 20 Medium to heavy frame with Networking 3 foots 6 inches or more in total Slate spacing 2 foots rock load section with medium (1.6-2/2)B meshing Black blasting 20 heavy frame with spacing 2 Networking 3 foots 6 inches or more in total Slate foots rock load (1.6-2/2)B section with medium meshing

Table 7: Determination of the supporting systems and drilling method with a 10/meter tunnel diameter based on geotectonic classification Lithology RMR Drilling method Support system Rock bolt with diameter shotcrete Metal of20mmand completely frame injected Ferrous 57 Drilling with upper quarry and lower Rock bolt with length of 4m Thickness 50- Not Dolomite platform .progress amount in upper and spacing 1.5-2min crest 100mmin crest necessary quarry is 1.5-3mafter 10m, support and walls .mesh coil in and30mmin walls system progress is performed crest Thick 65 Drilling with all section progress is 1- Local Rock bolt with Thickness 50mm Not layer 1/5m support system is implemented length of 3m, spacing in crest (if necessary limestone with distance 20mfrom quarry 2.5m2min crest .mesh coil in necessary) crest(if necessary) Orbitolina 57 Drilling with upper quarry and lower Rock bolt with length of 4m Thickness 50- Not Limestone platform .progress amount in upper and spacing 1.5-2min crest 100mmin crest necessary quarry is 1.5-3mafter 10m, support and walls .mesh coil in and30mmin walls system progress is performed crest

Support system has been determined based on Q index and equivalent dimension for different lithology in the tunnel direction.

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Table 8: The determination of support system based on Q index and equivalent dimension Lithology Q Suggested Support system Black 1/56 Rock bolt with shotcrete reinforced with the supported steel fiber, with thickness up to 50- Slate 90mm Orbitolina 4/14 Systematic Rock bolt with shotcrete with unsupported steel fiber with thickness of40-100mm Limestone Orbitolina 3/33 Systematic Rock bolt with shotcrete with unsupported steel fiber with thickness of40-100mm Limestone Ferrous 6/2 Systematic Rock bolt with shotcrete with unsupported steel fiber with thickness of40-100mm Dolomite Thick 8/33 Systematic rock bolt layer limestone

Stand up time based on Q index and RMR One of effective parameters on drilling is stand-up time estimation. In order to determine the stand-up time in the tunnels where are excavated by blasting method, using advantage from geo- mechanical classification and tunnel diameter, for obtained RMR in table 3supporting systems show in table 7 and stand-up time of the tunnel are a the follows : 1- In ferrous dolomite and orbitolina limestone, stand-up time of the tunnel is one week without supporting. 2- In thick layer massive limestone, stand-up time of the tunnel is three weeks without supporting. Maximum unsupported tunnel diameter for the different rock masses with different qualities using Q index includes: black Slates: 3 meters; orbitolina limestone: 4 meters; ferrous dolomite: 4/5 meters and thick layer massive limestone: 5meters. Maximum pressure exerted on supporting systems was obtained based on the value of RMR: Pv = (0.248-0.279Mpa) which is in a good range.

Dominant tension and sliding wedges formation in the tunnel direction

In the tunnel direction, 122 joints were collected. The joints were entered in software Stereo32 and results are shown in figure (4a). In order to predict and estimate tension in the tunnel direction, initially the joints with more frequency and the characteristics of the tunnel direction were entered in non-wedged software. Figure (4b) shows the tunnel direction and 3 main joints.

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a b

c d Figure 4: Tensions in different parts of the direction of Khansar-Boien Miyandasht tunnel and the prediction of sliding wedges

As it can be seen in figure (4c) (from north direction), tension in the left ceiling and wall as well as right wall is more than other points. Also it shows the characteristics of the formed wedges. Tension is not hazardous on the floor of tunnels. Figure (4d) shows sliding wedges in the tunnel direction. The most important wedge is upper-left wedge. Second wedge is upper-right wedge. Two wedges are made in lower part of the tunnel. In general, since the distance of the joints is medium and the region appears block by block, some parts of the tunnel may collapse. It is important that output diameter of the tunnel has an inverse dextral fault. As mentioned before, shearing state and soapy touch confirms the function of this fault in the depth of 148 meters. It is predicted instable wedge of the tunnels, direction will be formed in the left wall and ceiling based on three groups of dominant joints in the stations near the tunnel and their repetition and continuation in short distances due to high rate of crushing in the region(figure 4a). Maximum tension and hazard is formed in the mentioned part (figure: 4d). A fault perpendicular to the tunnel direction was found in output aperture of the tunnel that acted as an inverse dextral fault. This fault may create slides during drilling, because air photographs indicate the displacement of quartz sediments indicating that fault is active.

CONCLUSION From a tectonic viewpoint, considering faults, it is concluded that except for Dalan and Khansar faults that follows direction of Zagros; other faults are limited to syncline, which mostly include normal and inverse faults. Mentioned faults have low length and they are limited to upper and lower Cretaceous. It is most likely that they are result of folding. Collected joints of the region include: Vol. 20 [2015], Bund. 7 1762

Collection site Dip Dip Tunnel Tunnel Reaction direction strike ° Upper cretaceous 230-240 50 - N10E Good 55° lower cretaceous 290-310 60°- N10E Good 85° ° lower cretaceous 110-140 85 - N10E Very unsuitable 90° Shearing zone 330-350 55°- N10E Good 80° Shearing zone 250-280 70°- N10E Good 80° ° Shearing zone 145-180 35 - N10E Unsuitable to 60° suitable ° In Jurassic, high ;in upper and lower 40 45 N10E suitable cretaceous, low In Jurassic, high ;in upper and lower 55 40° N10E suitable cretaceous, low In Jurassic, high ;in upper and lower 35 25° N10E suitable cretaceous, low Upper cretaceous 185-200 35°- N10E Unsuitable to 60° suitable

The above pattern about joints can be considered in the establishment of underground engineering projects such as mines tunnels and dams, foundation. Also it can be used in more precise designs and calculations of the structures. A group of these joints is not active and the other group of them has been filled by secondary materials such as calcite, silica and clay which have been consolidated. Therefore, the position of dominant joints can be useful in tunnel drilling orientation, slide reduction, falling reduction and non-hardening of the tension in blasting. Fractures arrangement shows progressive deformed shearing zone. In this arrangement, Khansar fault is main dextral inverse shearing zone and other fractures are its riddle shears. Since Khansar-Boien Miyandasht tunnel is almost perpendicular to the axis of the syncline, it is the best case for drilling from a geological engineering viewpoint. But it should not be ignored the fault located in the external aperture that has acted as a dextral inverse fault perpendicular to the tunnel direction. It can cause the slides during drilling and considering created offset and quaternary sediments displacements, it may be hazardous. Therefore, necessary strategies should be considered in this regard. Given the region tectonics and investigated stations and obtained values based on RMR and Q, the type of support is suggested is as the fallow: Q method: Rock bolts systematically for thick layer massive limestone, systematic rock bolt with shotcrete without reinforcement with the thickness of 40 to 100mm for orbitolina limestone, ferrous dolomite and rock bolt with shotcrete reinforcement with steel fiber with the thickness of 50-90mm for the black slates. RMR method: For orbitolina limestone and ferrous dolomite, drilling with upper quarry and lower platform progress amount in upper quarry is 1.5-3m after 10m, support system progress is performed. Rock bolt with diameter up to 20mm and completely injected. Rock bolt with length up to 4m, spacing up to 1.5-2m in the crest and walls, mesh coil in crest. Shotcrete with the thickness up to Vol. 20 [2015], Bund. 7 1763

50-100mm in crest, and 30mm in walls. Metal frame is not necessary. For thick layer massive limestone, drilling is performed as all section, progress amount is 1-1/5m support system is implemented with distance 20m from quarry. Rock bolt with diameter of 20mm and completely injected. Local rock bolt with length of 3m, spacing 2.5m 2m in crest, mesh coil in crest (if necessary). If is necessary, shotcrete with the thickness up to 50mm in crest (if necessary). Metal rib is not necessary.

It should be known ơ1 is entered in the direction of the tunnel from SW and ơ3 is perpendicular to the tunnel direction. Because splays of Khansar fault including Mobarakeh, Dizicheh and Zarinshahr are active in terms of tectonics (because of Zayandehrood displacement in quaternary period) and it has dextral inverse transpression, necessary strategies should be considered in order to support this structure, because possible activity of Zagros may cause tension accumulation and make it active. Khansar area is in medium hazard range in slide hazard map of Iran, but it is next to the high-hazard region. Given recent earthquakes in Golpaiegan and Isfahan (2013), this project needs complete predictions of civil engineering and geological engineering.

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