GASCLAY - Construction drawings of the Gas Fracturing Visualisation Rig

Drawings of a new experimental device for the visualisation of fluid-driven cracks in clays. In the proposed experimental device, a thin layer (~1mm) of clay paste is compressed between two transparent discs of 110 mm diameter and 50 mm height. The bottom disc has a central hole through which a steel pipe is inserted to inject the fluid at the centre of the clay sample through a tip filter. A perimeter filter contains the sample laterally while allows to control the back-pressure during the fluid injection. The transparent discs and the perimeter filter are positioned by means of three steel rings, which are guided by four precision shafts. The compression of the clay sample is achieved by tightening nuts at the threaded ends of the shafts.  The device is instrumented with four donut load cells (one per shaft) placed in between the tightening nuts and the top ring to measure the compression forces, two displacement traducers (LVDT) to measure the relative displacement of the transparent discs, and fluid pressure transducers connected to the injection pipe and to the perimeter filter. The experimental setup is completed with two high-precision high-pressure pressure-volume controllers, that permit to control fluid injection rate and the back-pressure. In addition, pictures are taken with a high-resolution camera at a regular rate during the fluid injection, through the top transparent disc. To enable the detection of thin cracks, the device and the camera are placed in a dark box, with a collimated backlight panel placed under the bottom transparent disc.  This device has been developed as part of the GASCLAY project funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101028292. <br>

用于可视化黏土中流体驱动裂缝的新型实验装置设计图。在所提出的实验装置中，一层厚度约1毫米的黏土浆体被压缩在两个直径110毫米、高度50毫米的透明圆盘之间。底部圆盘开设有中心孔，钢管穿过该孔，并通过尖端过滤器向黏土试样中心注入流体。周边过滤器可在侧向约束试样的同时，调控流体注入过程中的背压。透明圆盘与周边过滤器通过三个钢制圆环实现定位，该定位结构由四根精密导向轴进行导向。黏土试样的压缩载荷可通过拧紧转轴螺纹端的螺母进行调控。该装置配备了四个环形测力传感器（每根转轴对应一个），安装于拧紧螺母与顶部圆环之间，用于测量压缩载荷；同时设有两个位移传感器（Linear Variable Differential Transformer，简称LVDT），用于监测透明圆盘的相对位移；此外还配备了与注入钢管及周边过滤器相连的流体压力传感器，用于采集流体压力数据。本实验装置还配有两台高精度高压容积控制器，可分别调控流体注入速率与背压。此外，在流体注入过程中，可通过顶部透明圆盘，由高分辨率相机以固定帧率拍摄试样图像。为实现细微裂缝的清晰检测，装置与相机均置于暗箱内，底部透明圆盘下方设有准直背光板。本装置为欧盟地平线2020（Horizon 2020）研究与创新计划下玛丽·斯克沃多夫斯卡-居里资助协议（编号101028292）资助的GASCLAY项目的研发成果之一。