A reactor shutdown would typically initiate with a trip signal following a postulated Loss of Coolant Accident (LOCA). The Emergency Core Cooling System (ECCS) assures fuel cooling by flooding the core and recirculating coolant inside the channels for long-term decay heat removal from the fuel. When the primary flow is interrupted, and simultaneously the ECCS is severely impaired or failed, fuel cooling tends to degrade, leading to the heat-up of fuel and coolant channels. Analysis indicates that further progression of such accidents in Pressurized Heavy Water Reactors (PHWRs) is primarily delayed due to the huge water mass in the calandria vessel around the reactor core. However, the horizontal orientation introduces several phenomenological complexities introducing complexity in formulating the Severe Accident Management Guidelines (SAMGs). For a postulated unmitigated low-pressure accident scenario, the accident progresses with the channels heating up, and creep sagging under thermal load and channel and fuel weight. The sagged channel contacts the channel below, transferring heat and its load. With further progress, it is postulated that the supporting channel would fail, and leading to a cascading core collapse.The present paper discusses the experimental studies carried out on multiple channel sagging and disassembly phenomena envisaged during the mid-phase of a severe accident. It is challenging to perform full-length experiments; hence, scaled-down channels were used in the experiments. The postulated accident condition is a significant break LOCA with loss of ECCS and loss of all heat sinks. The experimental setup consists of three channels placed vertically in a fixed lattice pitch forming three distinct channel rows. The paper compares two possible situations or test cases: 1) all three channels are heated, 2) the top two channels are heated, and the lower channel is unheated. The lower channel is an unheated (dummy) channel supporting the upper deforming channels. Finally, a multi-channel sagging deformation mode has been postulated based on the experimental observations. The contact propagation along the contacting surface is found to be a time-dependent event, indicating a channel's rate-dependent elongation. The middle CT is compressed between the upper and lower channels, compromising its structural support for middle PT.