Tunneling in Difficult Ground

Tunneling in Difficult Ground Study on Pre-support methods in conventional tunneling

Prepared by “M. Taromi”

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

INDEX Introduction Improving face stability with Sequential Excavation Method (SEM) Improving face stability with Umbrella Arc Method (UAM) Improving face stability with jet-grouting arch Improving face stability with Face Bolting Improving face stability with Combined Method Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Chapter 1: Introduction Soil Reinforcement Types in Conventional Tunneling Method

Face Reinforcement

Steel Pipe Umbrella Sequential Excavation Method

Steel Arch Micro pile

Chapter 1: Introduction • Soil Reinforcement Types in Conventional Tunneling Method • Steel Pipe Umbrella

Steel Arch • Micro pile Face Reinforcement

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Chapter 2: Improving face stability with Sequential Excavation Method (SEM)

Hakim tunnel, 2015, Tehran, Iran

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Tartaiguille tunnel (France, Marseilles 1998)

Chapter stability with Sequential Method Chapter23:Improving Improvingface face stability with SequentialExcavation Excavation Method(SEM) (SEM) Effects of reducing face size : • Face extrusion is proportional to size • 3-D effects (face arching – horiz. plane)

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Chapter 2: Improving face stability with Sequential Excavation Method (SEM) Performance mechanism of full face excavation

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Chapter 2: Improving face stability with Sequential Excavation Method (SEM) • • •

Tunnel Type: Twin Tunnel

Excavatiom Method: NATM/SEM Total Lenght: 3256 m

• Cross Section Type: 3.5 lanes • Cross Section Area: 186 m^2 • Excavation Width: 18 m

• Excavation Height : 12.6 m • Roadway Width: 13.5 m • Free Height: 5.6 m

• Speed Limitation: 60 km/hr Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Introduction

Chapter 2: Improving face stability with Sequential Excavation Method (SEM)

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Introduction

Chapter 2: Improving face stability with Sequential Excavation Method (SEM) Factor

The city of Tehran is founded on Quaternary alluvium, which

Age

has been geologically classified by Rieben.

Rieben (1966) was a European geologist who worked for the Geological Survey of Iran (GSI) in the mid 20th century.

Rieben (1966) divided the Tehran coarse-grained alluvia into

four categories, identified as A, B, C and D, where A is the oldest and D the youngest.

According to geology and geotechnical investigations and

results of 20 boreholes with 25–45 m depth and 24 test pits with 10–30 m depth which were excavated to examine

subsurface layer conditions along the Niayesh tunnels routes, The tunnel will pass through A and B formations.

Lithology Cementation Grain size Dip layer (deg) Thickness (m) Sedimentary environment Other name (local name) Location of observation in Tehran

Islamic Azad University - Islamshahr Branch Department of Geotechnical Engineering

Alluvium A 5 Ma Homogeneous conglomerate

B 700 ka Heterogeneous conglomerate

Cemented and hard

Variable, but usually weak cement

0–90

0–15

Clay to 100–250 mm Maximum 1200 Fluvial

Hezardareh alluvial formation North area

Very variable up to several metres

Maximum 60 (thickness decreases toward south) Fluvioglacial and periglacial North Tehran heterogeneous alluvial formation North area

C 50 ka

Alluvial fan

Cementation less than A and nonhard Clay to 100–200 mm 0

Maximum 60 Fluvial

Tehran alluvial formation

North and central area

D 10 ka

Recent alluvial

Non-cemented Clay to several metres 0