Tunnel Forepoling (Forepoles)

Tunnel forepoling (forepoles)

Tunnel forepoling (forepoles) refers to the placement of near-horizontal steel bars/pipes/sections around the periphery of the heading to form a rock support cage in weak zone areas. To support the excavation roof or tunnel crown, in other words. Forepoling should be used on rock and soil conditions that are prone to overbreak, collapses, or material inflow immediately after the following excavation. It shall be applied locally or systematically, depending on the circumstances, for the safety of the works and the prevention of overbreak. According to Warner forepolling should be densely installed to reduce the influences from stress-release at the face and the crown. Face bolts only contributed to stress-release at the face. Forepolling divides the surrounding ground of the installed area into two zones; i) outside the zone of the invisible arch consisting of forepoles and ii) inside the zone of the forepoles.

Forepoles, by definition, have a larger diameter than spiles and are longer than the depth of excavation. Within these weak rock regions, the length of forepoles exceeds the ensuing plastic region around and ahead of the face. The forepoles can be installed at a shallow angle from the horizontal in the tunnel alignment's longitudinal direction. The ideal angle ranges from 3^o to 8^o, with a spacing range of 30-60 cm center to center. The spacing is determined by the need to create an arching effect, which necessitates the overlapping of forepoles.

The size of the forepoles, which have an outside diameter of 60–168.3 mm and a wall thickness of 5–10 mm, also defines the arching effect. Depending on the installation system and support elements, different nomenclatures are described. These are: I forepoles grouted arch, ii) forepoles confined arch, iii) forepoles double grouted arch, iv) forepoles double continuous grouted arch, v) forepoles continuous grouted arch, and vi) forepoles open grouted. All of these temporary support categories for forepoles are successfully used in a variety of projects around the world.

Chemical grout-treated ground (injected in periphery holes drilled ahead of the face) and/or angled steel bar installations (grouted bolts) aimed at keying plates or blocks together before undermining can also be referred to as forepoling. Proctor and White's "Rock Tunneling with Steel Supports," published by Commercial Shearing, and the same authors' "Earth Tunneling with Steel Supports" are two old but good descriptions of conventional forepoling.

Comments

पर बाट देशलाई हेर्दा।

परदेश बाट देशलाई हेर्दा। हाम्रो आफ्नै भुगोल छ। भाषा छ। आफ्नै धर्म छ। देवता छ्न आफ्नै। नभएको त बुझाइ मात्र हो। आफ्नै इतिहास छ। भित्तामा आफ्नै पात्रो छ। गति आफ्नै छ। नभएको त गति तिब्र मात्र हो। सन्सार हेर्नलाई सगरमाथा छ। फेर्नको लागि सफा हावा छ। अन्नको लागि तराइको फाट छ। भिमकाय पहाड छ्न, खानी छ, मुलको पानी छ नहुनु पर्ने चाँइ हैरानी मात्र हो। आफ्नै गित छ्न संगीत छ्न। गायक छ्न गायिका छ्न। चलचित्र पनि आफ्नै छ्न। हिरो छ्न, हिरोईन छ्न। खड्किन थालेको चाइ आफ्नै कथा हो। हामी सग के छैन? हामीसग हिड्नलाई बाटो छ। पुरानो सभ्यताको पाटो छ। आफैले आर्जेको देशको माटो छ। नहुन पर्ने चाइ जात-धर्मको नाउँमा फाटो हो। हेर्ने हो भने हामी सग पहिला नै धेरै कुरा छ्न। बिधुतको लागि खोला-नदि छ्न। पर्यटनको लागि सुन्दर प्रकृति छ। सन्तुलित हावा पानी छ। न बनाय हुने भनेको दुत्सित मात्र हो। बिद्यालय छ्न। बिश्वबिद्धालय छ्न। बिध्या पिठ छ्न। बिद्यार्थी छ्न( अहिले सम्म) खड्किएको भनेको देशलाइ चाहिने पाठ्यक्रम र पठन पाठन हो। सानो भूगोल भैकन पनि हाम्रो देश सग धेरै कुरा छ। हिमाल छ। हिमालमा हिउँ छ( अहिले सम्म) सबै हिमाल विशाल छ्न।

मेरो साधारण बुझाइ, यो दौड हो कि भागदौड ?

मेरो साधारण बुझाइ, यो दौड हो कि भागदौड ? जिजुबुवाहरु कतै जानुभएन। धेरै हिड्नु पर्ने बाटो अप्ठ्यारो भएर हो कि वा आफ्नै माटोमा सबै थोक देखेर हो, गाउँ घर तिरै रमाउनु भयो। हजुरबा पुस्ता अलि पर भारत बर्मा सम्म पुग्नु भयो। केही पढ्नुभयो केही नयाँ कुरा सिकेर आउनुभयो। तर उतै हराउनु भएन। गाउँ फर्किएर गाउँ मै अर्थोपार्जन र बिधालयहरु स्थापना गर्नु भयो। बाउहरुको लागि सपना देख्नु भयो। खेतवारि जोडि घर धनसार बनाउनु भयो।बुवा पुस्ताले बिधालयमा केही पद्न पाउनु र नया कुरा सिक्न पाउनु भयो। यो पुस्ताले हजुरबाहरुको सपना बुझेन्न वा आफ्नै सपना पूरा गर्न भौतारियो, कोहि बिदेश गए कोहि शहर पशे। बिदेश जाने थोरै थिए धेरै फर्किए, पछि आफनै थाक थलोमा। शहर पस्नेहरु शहर मै हराए। नातिहरु जन्मिने क्रम जारि नै रह्यो। नाति हरु ठुला हुन्दा सम्म धेरै ठाउँ बाटो ले जोडियो। सन्चार माध्यमले धेरै मान्छेहरुसग जोडिए। नयाँ कुरा धेरै थाहाँ पाए। सपना र चाहाना पनि तेहि अनुसार परिवर्तन भयो। देशले मात्र उनिहरुका चाहाना पुर्याउन सकेन भनुम।धेरै लागे बिदेश। अहिले सम्म लागिरहेछ्न । अब पनाति हरु उतै जन्मिने भए, उनिहरुको सपना यो धर्तीले थेग

Chungthang Hydro-Dam Breach: Lessons for Nepal's Big Hydropower Ambitions

Chungthang Hydro-Dam Breach: Lessons for Nepal's Big Hydropower Ambitions Introduction: A catastrophic glacial lake outburst triggered flash floods in North Sikkim's Mangan district on October 4, 2023, leading to the breach of Sikkim's Chungthang dam, the largest hydropower project in the state. This incident has sent shockwaves through the region, emphasizing the need for Nepal to carefully assess the risks associated with large hydropower dam projects. To make informed decisions, Nepal must draw lessons from past dam failures and natural disasters, understanding the implications of such events on a national scale. The Chungthang Hydro-Dam Disaster: The Chungthang dam, a vital component of the 1200 MW Teesta Stage III Hydro Electric Project, is a symbol of power generation in the region. However, the recent breach underscores the potential consequences of dam failures. As flash floods wreaked havoc in Chungthang and Mangan districts, damaging infrastructure and lea

फरक पाना| Zircon Creations

Search This Blog