月球与火星环境约束下孔压静力触探机理及适用性差异研究进展与展望

Research progress and prospects on piezocone penetration testing mechanisms and applicability under environmental constraints of Moon and Mars

摘要

【目的】静力触探(Cone Penetration Test,CPT)及其孔压扩展形式孔压静力触探(Piezocone Penetration Test,CPTU)在地球岩土工程中已形成较成熟的观测—解释体系,其核心观测量包括锥尖阻力q_c、侧摩阻力f_s和孔压u₂。当地球CPTU向月球与火星浅表层探测拓展时,低重力、近真空/稀薄大气、强热循环以及含冰、含盐、胶结和不饱和风化层等因素将系统性改变贯入过程中的应力路径、边界条件、测量链稳定性及观测响应的可解释性。针对月球水资源勘探开发及火星浅表层工程探测需求,系统评述月球与火星环境约束下类CPTU的响应机理、适用边界及技术发展方向。【方法】以地球CPTU解释基线为参照,围绕“环境约束—测量链路—指标响应—解释边界”的主线,结合月球极区含冰风化层、月球非极区近地表工程场景和火星候选平原取样/钻探场景,综述低重力、真空/稀薄大气、含冰/含盐/不饱和介质及现有探测任务资料对q_c、f_s、u₂形成机制和解释框架的影响,并讨论系统改进、多传感联合约束、地面等效校准与小样本条件下的概率解释思路。【结果】低重力的影响并不只是降低原位应力水平,还会改变反力供给、姿态稳定性和贯入边界条件,使q_c和f_s更易呈现突变型或阈值型响应,削弱地球经验图谱及连续参数反演关系的直接迁移性。近真空或稀薄大气及热循环会显著影响孔压测量链稳定性,使u₂在地外场景中更适合作为经状态诊断后方可使用的条件性辅助观测量。在月球近真空条件下,当其物理归因不明确时,不宜直接用于土体力学参数反演。含冰、含盐、胶结和分层结构进一步增强了贯入响应的非唯一性,在现有证据条件下,分层识别、界面识别及事件型响应分析通常更适合作为复杂介质条件下的优先解释路径。现有任务资料可为承载水平、浅层结构和推进边界提供外部约束,但尚不能直接替代标准CPTU校准体系。【结论】月球与火星场景中的类CPTU研究,关键不在于简单复制地球三通道配置,而在于面向任务场景重构“测量链路—推进边界—多源约束—解释评估”框架。后续研究应重点推进低重力条件下的地面等效校准、真空/热循环环境中的孔压测量稳定性验证、含冰/含盐风化层贯入机理及其适用边界研究,以及地面等效数据库和不确定性分级解释体系建设,以支撑月球水资源探测和地外浅表层工程勘查中的类CPTU技术发展。

Abstract

[Objective] Cone penetration testing(CPT) and its pore-pressure extension, piezocone penetration testing(CPTU), have formed a relatively mature observation-interpretation framework in terrestrial geotechnical engineering, with cone tip resistance(q_c), sleeve friction(f_s), and pore pressure(u₂) as the core measured parameters. When terrestrial CPTU is extended to shallow subsurface exploration on the Moon and Mars, factors such as low gravity, near-vacuum or rarefied atmospheric conditions, intense thermal cycling, and ice-bearing, saline, cemented, and unsaturated regolith can systematically alter stress paths, boundary conditions, measurement-chain stability, and the interpretability of measurement responses during penetration. To meet the demands of lunar water resource exploration and Martian shallow subsurface engineering investigation, the response mechanisms, applicability boundaries, and technical development directions of CPTU-like techniques under lunar and Martian environmental constraints are systematically reviewed. [Methods]Taking the terrestrial CPTU interpretation framework as the reference baseline, the analysis follows the main line of “environmental constraints-measurement chain-response indicators-interpretation boundaries. ” It examines three representative mission scenarios: ice-bearing regolith in the lunar polar regions, near-surface engineering conditions in non-polar lunar regions, and sampling/drilling scenarios in candidate Martian plains. On this basis, the impacts of low gravity, vacuum or rarefied atmosphere, ice-/salt-bearing and unsaturated media, and existing mission observations on the formation mechanisms and interpretation framework of q_c, f_s, and u₂ are synthesized. Additionally, possible directions for system improvement, multi-sensor joint constraints, ground-equivalent calibration, and probabilistic interpretation under small-sample conditions are discussed. [Results] The impact of low gravity is not merely limited to reducing the in situ stress level. It also alters the reaction force supply, attitude stability, and penetration boundary conditions, making q_c and f_s more prone to exhibiting abrupt or threshold-type responses. This undermines the direct applicability of terrestrial empirical charts and continuous parameter inversion relationships. Near-vacuum or rarefied atmospheric conditions and thermal cycling significantly affect the stability of the pore-pressure measurement chain, making u₂ more suitable as a conditional auxiliary observation parameter in extraterrestrial scenarios that can be used only after state diagnosis. Under the near-vacuum conditions on the Moon, when its physical attribution remains unclear, u₂ should not be directly used for the inversion of soil mechanical parameters. The presence of ice, salts, cementation, and layered structures further enhances the non-uniqueness of penetration responses. Given the current evidence, layer identification, interface identification, and event-type response analysis are generally more appropriate as priority interpretation approaches under complex media conditions. Existing mission data can provide external constraints on bearing capacity, shallow structure, and penetration boundary conditions, but they cannot directly replace the standard CPTU calibration system. [Conclusion] For lunar and Martian applications, the key to CPTU-like investigation does not lie in simply replicating the terrestrial three-channel configuration, but in reconstructing a mission-oriented framework that integrates the measurement chain, penetration boundary conditions, multi-source constraints, and interpretation/evaluation. Future efforts should focus on ground-equivalent calibration under low-gravity conditions, validation of pore-pressure measurement stability under vacuum and thermal cycling, investigation of penetration mechanisms and applicability boundaries in ice-/salt-bearing regolith, and development of ground-equivalent databases and tiered uncertainty-based interpretation schemes, so as to support the advancement of CPTU-like techniques for lunar water resource exploration and extraterrestrial shallow subsurface engineering investigations.

关键词

CPTU / 月球/火星环境 / 贯入机理 / 原位测试 / 月球风化层 / 火星土壤 / 浅表层探测 / 影响因素

Key words

CPTU / lunar/Martian environment / penetration mechanism / in situ testing / lunar regolith / Martian soil / shallow subsurface exploration / influencing factors

基金资助

国家杰出青年科学基金项目(42225206)

国家自然科学基金面上项目(42572345)

安徽省自然科学基金面上项目(2508085MD087)

安徽省教育厅科研项目(2025AHGXZK20082)

安徽省教育厅科研项目(2025AHGXZK50042)