The deep in-situ environment is often characterized by high pore pressure, which will be released during traditional coring in deep rocks and lead to damage in rock samples. Hence, a novel coring technology has been proposed and systematically investigated for preserving in-situ conditions, including pore pressure, to obtain rock samples with high fidelity to the deep in-situ environment. To theoretically examine the variation in pore pressure after coring and evaluate its influence on rock samples, two kinds of mesoscopic model representing closed-pore and open-pore were established and analyzed by stressflow coupling, in which both seepage in porous matrix and flow in relatively bigger cavities are considered. An elastic-plastic-damage model associated with volumetric dilatation was introduced to reflect tensile damage. The influences of pore pressure after different kinds of coring were simulated by a series of conceptualized models, and the results revealed three kinds of situations: Pore pressure removal, pore pressure release, and pore pressure preservation. During traditional coring, the high pore pressure will neither be sealed completely nor released suddenly because the rock matrix has low permeability. The higher residual permeation pressure in the rock matrix will be caused by lower permeability, larger closed cavities or smaller open cavities. During traditional coring, the coring-induced inner damage arises nearby closed cavities. Both the damage value and the damage zone are increased with decreasing permeability. However, extra tensile damages rarely arise during in-situ pore pressure-preserved coring, which technology can also retain in-situ high pressure. Hence, the in-situ pore pressure-preserved coring technology has great significance for eliminating the distortion effect of coring to the greatest possible extent.

Shallow resources are becoming increasingly depleted, deep resource exploration has become a global strategy. The design and testing of deep in-situ core samples are prerequisites for exploring deep resources; however, no in-situ condition-preserved coring and testing techniques and tools have been reported yet. Here, the first deep in-situ condition-preserved coring system (with the preservation of pressure, temperature, substance, light, and moisture) was developed that considers the effects of high water pressure and formation dynamic loads, along with an in-situ condition-preserved testing system. A pressure-preserved controller was designed, achieving the ultimate capacity of 140 MPa and 150 ℃. A temperature-preserved coring system combining active heating and passive insulation was constructed, realizing temperature preservation from room temperature to 150 ℃. Three generations of film-formation principles and methods were designed, achieving an excellent quality preserved rate, moisture preserved rate, and visible light barrier rate. Moreover, a deep in-situ condition-preserved coring system, and a simulated coring platform for large cores under in-situ environments was fabricated. A non-contact testing system was derived to cut and prepare specimens under in-situ environment and to perform non-contact non-destructive testing and true triaxial testing. The research findings can be successfully applied to deep coal and gas development, deep oil and gas resources assessment, and deep-sea sediment prospecting, achieving excellent application outcomes. This study provides important theoretical, technical and hardware support for deep in-situ rock physics and mechanics research and deep resource exploitation.