# C-TUNNEL > Structural Analysis of Circular and Non-Circular Tunnel Linings Canonical: https://www.ramcadds.com/products/c-tunnel Source: RAM CADDSYS product catalog — https://www.ramcadds.com/products Last verified: 2026-07-18 Categories: infrastructure-geotechnical C-TUNNEL is a tunnel lining design software for circular and non-circular tunnel cross-sections. It performs structural analysis of tunnel linings under various load conditions including ground pressure, water pressure, surcharge loads, and seismic effects, providing engineers with efficient tools for preliminary and detailed tunnel lining design. C-TUNNEL is tunnel lining pre-design software from itech, built with CETU — the French national tunnel research centre — on the CESAR-LCPC finite-element kernel. It implements the convergence-confinement method parametrically for circular and non-circular cross-sections under ground pressure, water pressure, surcharge and seismic loading. Models export directly into CESAR 2D for detailed analysis. RAM CADDSYS distributes C-TUNNEL in India. C-TUNNEL is a software tool dedicated to the pre-design ("draft") stage of tunnel projects, developed by itech — the company behind the CESAR-LCPC finite element suite — in collaboration with CETU, the French national tunnel research centre. Built on the proven CESAR-LCPC finite element kernel, it proposes the convergence-confinement method in a parametric and didactic way, letting engineers explore ground-support interaction and produce quick pre-design reports before committing to a full model. Integrated parametric studies help engineers understand the sensitivities and boundaries of a tunnel project early, and a model started in C-TUNNEL can be exported to CESAR 2D for more complex modifications and detailed finite element analysis. RAM CADDSYS distributes the CESAR-LCPC suite, including C-TUNNEL, in India. ## Key points - C-TUNNEL is a pre-design tool for tunnel linings, built by itech on the CESAR-LCPC finite-element kernel in collaboration with CETU, the French national tunnel research centre. - Its central method is convergence-confinement (ground-reaction) analysis, presented in a parametric, didactic way for circular and non-circular tunnel cross-sections. - Built-in parametric studies let engineers sweep ground and support inputs to map the sensitivities and boundaries of a tunnel design before committing to a full model. - A C-TUNNEL model exports directly into CESAR 2D, so pre-design work carries forward into detailed finite-element analysis without rebuilding the project. - C-TUNNEL analyses ground pressure, water pressure, surcharge and seismic loading on conventionally excavated (NATM) tunnel linings. - RAM CADDSYS distributes C-TUNNEL and the wider CESAR-LCPC suite in India, with licensing, training and technical support. - Purpose-built for the pre-design ('draft') phase of tunnel projects — engineers get fast, structured pre-design reports before committing to a full 3D model. - Implements the convergence-confinement method in a parametric, didactic way, making ground-support interaction transparent and quick to explore. - Built on the proven CESAR-LCPC finite element kernel, so the underlying numerics are the same engine used on major international tunnel projects. - Parametric studies are built in, letting engineers sweep key inputs and quickly understand the boundaries and sensitivities of a tunnel project. - A model started in C-TUNNEL can be exported to CESAR 2D for more complex modifications and detailed finite element analysis — no rebuilding from scratch. - Lowers the barrier to FE-based tunnel assessment for conceptual and feasibility work, where a full continuum model would be slow to set up. - Available in India with local licensing, training and support through RAM CADDSYS, the authorized distributor. ## Why engineers pick it - **Convergence-Confinement Method** — Implements the convergence-confinement (ground-reaction) method in a parametric and didactic way. - **CESAR-LCPC Finite Element Kernel** — Built on the proven CESAR-LCPC finite element kernel — the same engine used on major international tunnel and infrastructure projects. - **Built-In Parametric Studies** — Parametric study capability lets engineers sweep key inputs and quickly understand the sensitivities and feasible boundaries of a tunnel project during pre-design. - **Export to CESAR 2D** — A model started in C-TUNNEL can be exported to CESAR 2D for more complex modifications and detailed finite element analysis. ## Capabilities - **Convergence-Confinement Analysis** — C-TUNNEL implements the convergence-confinement (ground-reaction / characteristic-line) method, modelling the interaction between ground relaxation and support installation for conventionally excavated tunnels. - **2D Finite-Element Pre-Design** — Built on the CESAR-LCPC finite-element kernel, C-TUNNEL performs 2D finite-element analysis tailored to rapid tunnel pre-design rather than full detailed modelling. - **Parametric Studies** — Integrated parametric study capability lets engineers vary inputs such as ground parameters and support timing/stiffness. - **Quick Pre-Design Reports** — The tool is designed to produce quick pre-design ('draft') reports for tunnel projects, supporting conceptual and feasibility-stage decision-making. - **Export to CESAR 2D** — Models built in C-TUNNEL can be exported into CESAR 2D for detailed finite-element analysis. ## Applications - **Tunnel feasibility and concept studies** — Rapidly assess ground-support interaction and likely support requirements for a proposed tunnel during early feasibility and concept design. - **Conventional / NATM excavation pre-design** — Apply the convergence-confinement method to conventionally excavated (NATM / sequential excavation) tunnels to estimate ground relaxation and the response of the primary support. - **Parametric sensitivity assessment** — Run parametric sweeps of ground stiffness/strength and support characteristics to bound the design space and identify the governing scenarios. - **Pre-design hand-off to detailed FE analysis** — Use C-TUNNEL to set up and screen a project, then export to CESAR 2D for the detailed finite-element analysis stage. - **Teaching and training in ground-support interaction** — C-TUNNEL is well suited to training engineers and students in tunnel ground-reaction concepts. ## In depth ### Why use a dedicated pre-design tool before building a full tunnel model? Because early-stage tunnel decisions need a fast, structured estimate of ground-support interaction, not the time investment of a full 3D model — C-TUNNEL is built specifically for that draft stage. Feasibility and concept studies live under time pressure: an engineer needs to know quickly whether a proposed alignment, ground condition and support sequence are workable before a client commits budget to detailed design. Building a full continuum model for every option at this stage is slow, and the ground-reaction behaviour that governs a conventionally excavated tunnel — how much the ground relaxes before support engages — can get lost inside a heavier general-purpose analysis. C-TUNNEL is scoped to answer exactly that question. It implements the convergence-confinement method in a parametric, didactic form on the CESAR-LCPC finite-element kernel, so ground-support interaction stays visible and quick to interrogate rather than buried in solver output. The result is a quick pre-design ('draft') report engineers can use to screen options, size support and identify the load cases — ground pressure, water pressure, surcharge, seismic — that matter most before committing to detailed modelling. ### How does a project move from C-TUNNEL through to detailed analysis? C-TUNNEL screens a tunnel cross-section under the convergence-confinement method during pre-design, then hands the model to CESAR 2D for the detailed finite-element work once the concept is set. Engineers set up a circular or non-circular cross-section and apply the relevant loading — ground pressure, water pressure, surcharge and seismic effects — then run the convergence-confinement analysis on the CESAR-LCPC kernel. Because the parametric study capability is built in, the same setup can be swept across ground stiffness, strength or support-timing assumptions to bound the design space and flag the governing scenarios, rather than running one case at a time by hand. Once the pre-design is settled, the same model exports directly into CESAR 2D, where geometry, staging and material behaviour can be extended for detailed finite-element analysis — including, where the project calls for it, the wider CESAR-LCPC tools for tunnel boring machine (TBM) excavation and segmental lining. That draft-to-detail handoff means the early screening work in C-TUNNEL is not thrown away once a project moves past pre-design. ## Questions ### What is C-TUNNEL? C-TUNNEL is a software tool dedicated to the pre-design ('draft') stage of tunnel projects. Built on the CESAR-LCPC finite-element kernel, it lets engineers produce quick 2D pre-design analyses and reports, primarily through the convergence-confinement method. ### Who develops C-TUNNEL? C-TUNNEL is developed by itech (itech-soft.com), the company behind the CESAR-LCPC finite-element suite. CESAR-LCPC's numerical core originates from LCPC / IFSTTAR (now Université Gustave Eiffel), and C-TUNNEL was developed in collaboration with CETU, the French national tunnel research centre. ### Is C-TUNNEL the same as CESAR-LCPC? No. C-TUNNEL is a dedicated tunnel pre-design tool that runs on the CESAR-LCPC kernel. CESAR-LCPC (CESAR 2D/3D) is the full finite-element platform for geotechnical, tunnel and civil engineering analysis; C-TUNNEL is focused on quick draft-stage tunnel work and can export its models into CESAR 2D for detailed analysis. ### What analysis method does C-TUNNEL use? Its central method is the convergence-confinement (ground-reaction) approach, presented in a parametric and didactic way, supported by 2D finite-element computation from the CESAR-LCPC kernel. ### Is C-TUNNEL a detailed design tool or a pre-design tool? C-TUNNEL is explicitly positioned as a pre-design / 'draft' project tool. It is intended for quick conceptual and feasibility assessment; for detailed finite-element analysis the project is exported to CESAR 2D. ### Can I move a C-TUNNEL model into CESAR for more detailed analysis? Yes. Models built in C-TUNNEL can be exported to CESAR 2D, where the project can be extended with more complex geometry, staging and material behaviour for full finite-element analysis. ### Does C-TUNNEL support parametric studies? Yes. Parametric study capability is built in, so engineers can vary key inputs and quickly understand the sensitivities and boundaries of a tunnel project during pre-design. ### Does C-TUNNEL design tunnel lining reinforcement or check it against a design code? No. C-TUNNEL is a finite-element pre-design and analysis tool centred on ground-support interaction; it is not marketed as a code-based reinforced-concrete lining design tool. Engineers carry out code-based lining and reinforcement design separately, using the forces from the analysis as input. ### Is C-TUNNEL suitable for TBM / segmental lining design? C-TUNNEL itself is focused on convergence-confinement pre-design of conventionally excavated tunnels. The broader CESAR-LCPC suite provides dedicated tools for modelling tunnel boring machine (TBM) excavation and lining; for TBM and segmental-lining work, CESAR 2D/3D rather than C-TUNNEL is the relevant tool. ### Who typically uses C-TUNNEL? It is used by tunnel and geotechnical engineers for conceptual and feasibility-stage tunnel assessment, and it is also valuable for teaching and training because the convergence-confinement method is presented in a clear, parametric way. ### What kind of output does C-TUNNEL produce? It produces quick pre-design reports for tunnel projects, based on the convergence-confinement analysis and any parametric studies the engineer has run. ### Is C-TUNNEL available in India through RAM CADDSYS? Yes. RAM CADDSYS is the authorized distributor in India for the CESAR-LCPC suite, including C-TUNNEL, providing licensing, training and technical support for tunnel and geotechnical engineering teams. --- Full page: https://www.ramcadds.com/products/c-tunnel Pricing is quoted per territory and is deliberately not published. Talk to us: https://www.ramcadds.com/contact