原状枯落物覆盖对土壤温度及冻融过程的影响

为揭示枯落物在调节土壤温度及土壤冻融过程方面的作用, 对8 cm油松林原状枯落物覆盖(C8)、4 cm油松林原状枯落物覆盖(C4)、8 cm柞树林原状枯落物覆盖(B8)和裸地(CK)4种处理条件下10 cm、20 cm、30 cm、40 cm、50 cm和60 cm深度的土壤温度进行监测, 结果表明: (1) 枯落物覆盖可以延长观测层土壤冻结期, C8观测层完成冻结比CK滞后18 d. (2) 枯落物覆盖对观测层土壤温度的影响具有双重性, 始冻期和完全冻结期具有保温效应, 解冻期主要为隔热降温效应. (3) 枯落物覆盖对30 cm以上土壤影响强于深层, C8处理下仅20 cm以上土层对气温变化敏感. (4) 枯落物对土壤温度的调解作用与覆盖枯落物的厚度和结构有关, 枯落物越厚, 结构越完整, 其调节土壤温度的作用越明显, 不同枯落物覆盖下的土壤温度差异系数为CK > C4 > B8 > C8.     

Preliminary Study on Loess Slumping Hazard between Northern Shaanxi and Western Shanxi along the Line of West-East Gas Transportation Project

INTRODUCTIONTheloess,widelydistributedinthenorthwestplateauofChina ,hasatalltimesbeenanimportantresearchsubjectofthestudiesonengineeringgeology.Duetotheunfavorableengineeringpropertiesofloess,aswellasthespecialtopog raphyandclimate ,thenorthwestloessplateauisaregionwithfrequentgeologicalhazardsandcomplicatedgeologicalengineeringproblems.Inthepast,mostoftheresearchersconsideredthelandslideasthemainandseriousformoffail ureoftheloessslopes,soloesslandslidesweregivenmoreattention (DuanandLuo…     

关于“衬砌工程冻害新思维”问题的商榷

中国农业大学低温工程试验研究室刘镜仁同志,在《渠道（沟）衬砌工程冻害治理的新思维及试验研究》一文中,提出了一些与《渠系工程抗冻胀设计规范》ＳＬ２３－９１相左的观点文章有针对性地论述了渠道衬砌中的冻害研究范畴、渠床的冻胀融沉和衬砌体的破坏、允许冻胀位移值与允许残余变形量等问题．并介绍了《渠系工程抗冻胀设计规范》编制中的一些情况     

高含冰量冻土路基融化固结规律研究

为了研究高含冰量冻土路基的融化固结规律，在线性大变形融化固结理论的基础上引入非线性本构关系，并运用分段插值法实现了孔隙比与压缩模量之间的非线性关系，完善了三维大变形融化固结数值模拟方法。在此基础上结合青藏公路实测数据验证了其合理性。研究结果表明，采用非线性应力?应变关系的大变形融化固结理论能够显著提高高含冰量冻土路基的沉降计算精度，并能够进一步合理描述热学场和力学场的相互叠加影响。冻土融化固结度受有效融化固结时间以及特征排水长度等因素的影响呈现出完全不同于融土路基的发展规律，即在路基运营初期其融化固结度上升，随着时间发展，其固结度在达到峰值后持续降低，这主要是由于融化深度持续增大后所引起的特征排水长度的增加和有效融化固结时间的缩短所造成的。因此，在计算高含冰量冻土路基稳定性设计指标时，应采用非线性应力?应变关系来进一步提高融化深度、沉降以及固结度等指标的计算精度。     

Evaluating model of frozen soil environment change under engineering actions

The change of frozen soil environment is evaluated by permafrost thermal stability, thermal thaw sensibility and surface landscape stability and the quantitatively evaluating model of frozen soil environment is proposed in this paper. The evaluating model of frozen soil environment is calculated by 28 ground temperature measurements along Qinghai-Xizang Highway. The relationships of thermal thaw sensibility and freezing and thawing processes and seasonally thawing depth, thermal stability and permafrost table temperature, mean annual ground temperature and seasonally thawing depth, and surface landscape stability and freezing and thawing hazards and their forming possibility are analyzed. The results show that thermal stability, thermal thaw sensibility and surface landscape stability can be used to evaluate and predict the change of frozen soil environment under human engineering action.     

Engineering geological characteristics and processes of permafrost along the Qinghai–Xizang (Tibet) Highway

Engineering geological problems of thaw-settlement and frost-heave occur frequently along the Qinghai–Xizang (Tibet) Highway (QXH) line and produce an adverse impact on roadbed stability. Eight monitoring sites were established along the QXH to investigate the engineering geological characteristics and environmental process of permafrost, including the upper and lower boundary of the active layer under the natural surface, the seasonal freeze–thaw depth under the asphalt pavement, the permafrost table temperature and roadbed stability. The investigation results show that the active layer thickness and permafrost table temperature under an asphalt pavement are higher than under a natural surface due to the absorption heat and reduced evaporation capability of the asphalt pavement. The implication for highway design and construction in permafrost areas are discussed.     

青藏高原多年冻土区沥青路面下融化盘形成变化特征

在青藏高原多年冻土区，沥青路面的辅设改变了地表与大气之间的热交换关系，尤其是路面水分蒸发量大量减少，致使路面突然升高，多年冻土层内能量积蓄增多，地温升高，上奶宵年下降。最终在路基下多年冻土顶板上形成融化夹层，并随时间延长，多年冻土顶板下降，融化夹层逐年扩大，多年冻土地下冰融化，路面破坏，严重影响道路运营。     

Experimental frost and salt weathering of chalk—II

Experiments are described in which chalk cubes were soaked in solutions of either sodium chloride, sodium sulphate, or magnesium sulphate at concentrations of 5·5 per cent and 12·5 per cent, or in a mixed solution of sodium chloride and sodium sulphate or in distilled water. After removal of excess liquid, the cubes were subjected to six freeze–thaw cycles with temperatures ranging from either +15 to ?10°C or +15 to ?30°C. The results confirm that frost weathering can be enhanced by the presence of certain salts, but the extent of weathering was much less than that previously reported for samples frozen totally immersed in the same liquids. Evidence is presented which suggests that salt crystallization is the major weathering process operative when non–immersed samples are frozen but a combination of frost and salt weathering operates when fully immersed samples are frozen.     

青藏铁路多年冻土区涵洞基础的冻融变形特征

对青藏铁路沱沱河试验段两座拼装式涵洞进行了地基地温及冻融变形监测，分析了涵洞多年冻土上限处的地温变化及地基的冻融变形特征。结果表明：涵洞地基的变形随地温的年波动变化。可分为冻胀和融沉两部分。冻胀变形小于下沉变形，涵洞基础的变形整体上表现为渐减沉降的特征；铁路路基及涵洞的修建改变了多年冻土原来的水热平衡，使涵洞多年冻土上限处地温产生正温波动，冻土上限产生变化。导致了涵洞地基土体沿涵洞纵向的不均匀变形。     

多年冻土热融滑塌的地温变化及滑坡过程分析

随着青藏高原工程强度的提高,冻土区斜坡稳定性成为工程建设必须面对和解决的问题,其中最为严重也是较难防治的斜坡失稳是热融滑塌.针对典型热融滑塌进行的温度监测资料表明,在滑塌的影响下,其下多年冻土地温年变化幅度趋小而年平均地温升高,导致产生这一现象的原因在于每年进入多年冻土的冷能有所降低.滑坡溯源侵蚀范围监测资料表明,滑塌范围的扩展随地温的周期变化波动进行,并主要集中在7～9月,最大扩展范围出现在沿坡体倾向方向.热融滑塌的产生与多年冻土条件和外因力的诱发关系密切,工程治理要考虑引起滑坡消亡的基本条件.