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>

黏土流体驱动裂缝可视化新型实验装置的设计图纸。在所提出的实验装置中，一层厚度约1 mm的黏土浆体被压缩于两个直径110 mm、高度50 mm的透明圆盘之间。底部圆盘开有中心孔，钢管穿过该孔，并通过尖端过滤器（tip filter）向黏土试样中心注入流体。外围过滤器（perimeter filter）可从侧向约束试样，同时在流体注入过程中调控背压。透明圆盘与外围过滤器通过三个钢制圆环实现定位，该组件由四根精密转轴导向。黏土试样的压缩载荷通过拧紧转轴螺纹端的螺母完成调控。本装置搭载了四类传感组件：四个环形测力传感器（donut load cells，每根转轴对应一个），安装于拧紧螺母与顶部圆环之间以测量压缩力；两台位移传感器（displacement transducers，LVDT），用于监测透明圆盘的相对位移；以及与注入钢管及外围过滤器相连的流体压力传感器，用于采集流体压力数据。实验装置还配备两台高精度高压容积式控制器，可精准调控流体注入速率与背压参数。此外，在流体注入全过程中，将通过顶部透明圆盘，由高分辨率相机以固定帧率采集图像。为实现细微裂缝的清晰检测，装置与相机被置于暗箱内，底部透明圆盘下方安装有准直背光面板（collimated backlight panel）。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-居里奖学金协议（编号101028292）资助的GASCLAY项目的研发成果之一。