Numerical investigation of geostress influence on the grouting reinforcement effectiveness of tunnel surrounding rock mass in fault fracture zones

Grouting is a widely used approach to reinforce broken surrounding rock mass during the construction of underground tunnels in fault fracture zones,and its reinforcement effectiveness is highly affected by geostress.In this study,a numerical manifold method(NMM)based simulator has been developed to examine the impact of geostress conditions on grouting reinforcement during tunnel excavation.To develop this simulator,a detection technique for identifying slurry migration channels and an improved fluid-solid coupling(FeS)framework,which considers the influence of fracture properties and geostress states,is developed and incorporated into a zero-thickness cohesive element(ZE)based NMM(Co-NMM)for simulating tunnel excavation.Additionally,to simulate coagulation of injected slurry,a bonding repair algorithm is further proposed based on the ZE model.To verify the accuracy of the proposed simulator,a series of simulations about slurry migration in single fractures and fracture networks are numerically reproduced,and the results align well with analytical and laboratory test results.Furthermore,these numerical results show that neglecting the influence of geostress condition can lead to a serious over-estimation of slurry migration range and reinforcement effectiveness.After validations,a series of simulations about tunnel grouting reinforcement and tunnel excavation in fault fracture zones with varying fracture densities under different geostress conditions are conducted.Based on these simula-tions,the influence of geostress conditions and the optimization of grouting schemes are discussed.

Tensile Fractures and in situ Stress Measurement Data Constraints on Cretaceous-Present Tectonic Stress Field Evolution of the Tanlu Fault Zone in Shandong Province,North China Craton

Tectonic stress fields are the key drivers of tectonic events and the evolution of regional structures.The tectonic stress field evolution of the Tanlu fault zone in Shandong Province,located in the east of the North China Craton(NCC),may have preserved records of the NCC’s tectonic history.Borehole television survey and hydraulic fracturing were conducted to analyze the paleo and present tectonic stress fields.Three groups of tensile fractures were identified via borehole television,their azimuths being NNW-SSE,NW-SE and NE-SW,representing multiple stages of tectonic events.Hydraulic fracturing data indicates that the study region is experiencing NEE-SWW-oriented compression and nearly-N-Soriented extension,in accordance with strike-slip and compression.Since the Cretaceous,the orientation of the extensional stress has evolved counterclockwise and sequentially from nearly-NW-SE-oriented to NE-SW-oriented and even nearly N-S-oriented,the stress state having transitioned from strike-slip-extension to strike-slip-compression,in association with the rotating and oblique subduction of the Pacific Plate beneath the NCC,with the participation of the Indian Plate.

Unconfined compressive strength and failure behaviour of completely weathered granite from a fault zone

Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests were conducted to investigate the mechanical characteristics and failure behaviour of completely weathered granite(CWG)from a fault zone,considering with height-diameter(h/d)ratio,dry densities(ρd)and moisture contents(ω).Based on the experimental results,a regression mathematical model of unconfined compressive strength(UCS)for CWG was developed using the Multiple Nonlinear Regression method(MNLR).The research results indicated that the UCS of the specimen with a h/d ratio of 0.6 decreased with the increase ofω.When the h/d ratio increased to 1.0,the UCS increasedωwith up to 10.5%and then decreased.Increasingρd is conducive to the improvement of the UCS at anyω.The deformation and rupture process as well as final failure modes of the specimen are controlled by h/d ratio,ρd andω,and the h/d ratio is the dominant factor affecting the final failure mode,followed byωandρd.The specimens with different h/d ratio exhibited completely different fracture mode,i.e.,typical splitting failure(h/d=0.6)and shear failure(h/d=1.0).By comparing the experimental results,this regression model for predicting UCS is accurate and reliable,and the h/d ratio is the dominant factor affecting the UCS of CWG,followed byρd and thenω.These findings provide important references for maintenance of the tunnel crossing other fault fractured zones,especially at low confining pressure or unconfined condition.

Response of underground pipeline through fault fracture zone to random ground motion

It is assumed that a pipeline is laid through a vertical fault fracture zone, and is excited by seismic ground motion modelled as stationary stochastic process. For horizontal incidence of waves, the cross-PSD （Power Spectral Density） function is developed using wave propagation theory, while for vertical incidence of waves the cross-PSD function is composed by auto-PSD model, coherence model and site response model. As the seismic input, the eross-PSD function is used to calculate the the axial and lateral seismic responses of underground pipeline through the fracture zone. The results show that the incident directions of seismic waves, width and soil property of the fracture zone have great influence on underground pipeline. It is suggested that the flexible joints with appropriate stiffness should be added into the pipeline near the interfaces between the fracture zone and the surrounded media.

Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

For four centuries now, southern Ghana has been known to be seismically active, and there is no clear geological explanation for the cause of the seismicity. By evaluating new field data and information with re-interpreted historical earthquake data of southern Ghana, the nature of the seismicity of southern Ghana has been elucidated. The mutual connection between the earthquake epicentres and the remote causes by Mid-Atlantic transform faults and fracture zones has been established. The seismic regions of southern Ghana have been linked separately to tectonic faults and activities of the St. Paul’s and Romanche transform-fracture zone systems offshore in the Gulf of Guinea to onshore. It is concluded that the seismicity of southern Ghana is due to tectonic activities of the St. Paul’s and Romanche transform-fracture systems. The Accra region earthquakes originate from reactivation of faults in the Romanche transform-fracture zone, and propagate onshore through Accra and environs. The Axim region earthquakes come from reactivated faults linked to the St Paul’s fracture zone, which go through southern Cote D’Ivoire to Ghana. Seismotectonic movements along the St Paul’s transform and fracture zones have quieted since 1879. But movement along the Romanche Transform fault and Fracture zone is active, causing ongoing seismicity of southern Ghana.

Failure responses of rock tunnel faces during excavation through the fault-fracture zone

It is essential to cast light on the construction risks in tunnel excavations through the fault-fracture zone(FFZ).This study adopts the material point method(MPM)to simulate the failure responses of a rock tunnel face during excavation through the FFZ.A numerical study was conducted to compare a physical model test and validate the feasibility of using the MPM in simulating tunnel face failure.One hundred ninety numerical simulation cases were constructed to represent a rock tunnel excavation project with different site con-figurations.The simulation results suggest that the cohesion and the friction angle significantly influence failure responses.The tunnel cover depth can magnify the failure responses,and the FFZ thickness significantly affects the mobilized rock mass volume when the FFZ consists of a weak rock mass.The numerical simulation results suggest three deformation patterns:face bulge,partial failure,and slide collapse.The failure responses can be characterized by stress arch,slip surface,angle of reposing,and influence range.The insights suggested by the face failure responses during excavation through the FFZ can aid field engineers in determining the scope of possible damage,and in establishing emergency measures to minimize losses if such failure occurs.

Integration of Electrical Resistivity and Electromagnetic Radiation Methods for Fracture Flow System Detection

An electrical resistivity and electromagnetic emission survey was carried out involving the use of vertical electrical soundings (VES) and natural pulse electromagnetic field of the earth (NPEMFE). The use of this new methodology managed to detect the fracture flow system rupture zones in the underground, also answered the questions about the deferent subsurface water bodies. The present study focuses on Marsaba-Feshcha sub-basin in the northeast of the Dead Sea. Due to the scarcity of boreholes in the study area, several geophysical methods were implanted. The combination of these two methods (VES and NPEMFE) with the field observations and East-West transversal faults with the coordination (624437/242888) was determined, cutting through the anticlines with their mainly impervious cores with fracture length of >400 m. These transversal faults saddle inside Nabi Musa syncline (Boqea syncline), leading to a hydraulic connection between the Lower and the Upper Aquifer. Due to the identified transversal fault, the water of the Upper and Lower Aquifer mixed and emerged as springs at Ein Feshcha group.

Numerical modelling of spatially and temporally distributed on‑fault induced seismicity:implication for seismic hazards

Induced seismicity is strongly related to various engineering projects that cause anthropogenic in-situ stress change at a great depth.Hence,there is a need to estimate and mitigate the associated risks.In the past,various simulation methods have been developed and applied to induced seismicity analysis,but there is still a fundamental diference between simulation results and feld observations in terms of the spatial distribution of seismic events and its frequency.The present study aims to develop a method to simulate spatially distributed on-fault seismicity whilst reproducing a complex stress state in the fault zone.Hence,an equivalent continuum model is constructed,based on a discrete fracture network within a fault damage zone,by employing the crack tensor theory.A fault core is simulated at the center of the model as a discontinuous plane.Using the model,a heterogeneous stress state with stress anomalies in the fault zone is frst simulated by applying tractions on the model outer boundaries.Subsequently,the efective normal stress on the fault plane is decreased in a stepwise manner to induce slip.The simulation result is validated in terms of the b-value and other seismic source parameters,hence demonstrating that the model can reproduce spatially and temporally distributed on-fault seismicity.Further analysis on the parameters shows the variation of frequency-magnitude distribution before the occurrence of large seismic events.This variation is found to be consistent with feld observations,thus suggesting the potential use of this simulation method in evaluating the risk for seismic hazards in various engineering projects.

Research on the 1879 South Wudu M8.0 Earthquake and Its Co-Seismic Fracture

Based on field investigations and indoor systematic research of the 1879 South Wudu M8.0 earthquake conducted in recent years, the magnitude, damage, seismic intensity, co-seismic fracture of the earthquake, as well as its seismogenic tectonics and preparation process, have been studied. The paper summarizes the results of studies on location of the earthquake’s macroscopic epicenter, magnitude and co-seismic fracture, with emphasis on the distribution range, type, extent and mechanism of its co-seismic fractures. The research reveals that, (1) the major part of the meizoseismal area of the South Wudu earthquake is located between Wudu and Wenxian in southern Gansu Province. It extends in a NEE direction, its shape is elliptical with the major axis about 70km long and the minor axis 30km. The macroscopic epicenter is located in the vicinity of Baoziba, in the east of the meizoseismal area; (2) three co-seismic fracture belts developed in the meizoseismal area, scattering northeastwards and converging southwestwards; (3) the major fracture belt extends from Baishuijiang at Hanan on the west, to the the bank areas of Bailongjiang river on the east, such as Gushuizi, Toufang and Daoqizi, etc.; (4) the co-seismic fractures consist of earthquake fissure, scarp, bulge, landslide, barrier lake and so on, among which landslides are the most obvious phenomenon; (5) according to the location, geometry and mechanism of the fracture, it is assumed that the co-seismic fracture zone of the South Wudu earthquake is the product of left-lateral strike-slip, associated with a dip-slip in the Hanan-Daoqizi-Maopola fault zone; (6) based on the size of the co-seismic fracture and the observed amount of displacement of the seismogenic fault of the South Wudu earthquake, the magnitude of this event is estimated to be M8.0.

深层-超深层致密储层天然裂缝分布特征及发育规律

天然裂缝是深层-超深层致密储层的有效储集空间和主要渗流通道,影响着致密储层油气的运移、富集、单井产能、开发方式及开发效果。通过对近年来致密储层裂缝研究成果总结和文献综述,分析了深层-超深层致密储层天然裂缝分布特征及发育规律。将致密储层天然裂缝分为大尺度裂缝、中尺度裂缝、小尺度裂缝和微尺度裂缝4个级别。不同尺度裂缝分布具有幂律分布的特点,裂缝尺度越大,数量越少;裂缝尺度越小,数量越多。大、中尺度裂缝主要起渗流作用,小尺度裂缝主要起渗流和储集作用,而微尺度裂缝主要起储集作用。在地层埋藏过程中的应力体制演化决定了不同时期天然裂缝的类型、产状及其力学性质;构造应力大小、岩石力学层的力学性质和厚度差异控制了多尺度裂缝的形成分布及其发育程度。构造变形导致不同构造部位的局部应力和应变分布产生差异,增强了裂缝发育的非均质性。逆冲断层通过控制其上盘地层变形控制了“裂缝域”的分布规律;走滑断层的组合样式、活动方式和岩石力学层共同控制了相关裂缝的三维空间展布。裂缝形成演化过程中的开启-闭合规律决定了裂缝的储集空间,记录了裂缝有效性的演化历史。

郁江走滑断裂带北部储集空间发育特征及主控因素

为探索走滑断裂破碎带储集空间发育特征和形成机理,综合应用野外露头、遥感影像和岩心测试资料,对郁江走滑断裂带北部储集空间进行识别刻画和量化分析,并探讨其发育主控因素。结果表明:郁江走滑断裂带北部破碎带在平面上可分为北部张扭段和南部压扭段,不同段储集空间发育特征存在差异,张扭段裂缝开度更大,压扭段裂缝长度、裂缝线密度、破碎区面积和洞穴面积更大,总体上,压扭段储集空间发育规模相对较大;走滑断裂带构造应力是决定优势储集空间发育的外部因素,岩层厚度和岩石矿物组成是控制储集空间发育的内部因素,岩层厚度大于1 m且碳酸钙含量低于70%的碳酸盐岩经压扭作用改造后,可形成缝洞型储集体有利发育区。

四川盆地PT1井区海相地层工程地质特征研究

PT1井区超深海相地层钻井过程中气侵和井漏频发,严重制约该区块的安全高效开发。文章基于有效应力法,利用最优化方法开展了海相地层孔隙压力评价;结合断层和裂缝发育程度探讨了PT1井区气侵和井漏纵横向分布特征。结果表明,受异常高压和裂缝发育程度的双重影响,气侵主要发生在龙潭组,占比达40%;井漏主要发生在筇竹寺组和灯影组,占总漏失量的80%以上。气侵与异常压力、裂缝发育程度、断裂情况等因素有关,异常高压是气侵内在的原因,而断裂带和发育的构造裂缝为气侵提供了必要条件。井漏层位和漏失量主要受一、二级大型断裂带控制,不同断裂带的影响具有显著的叠加效应,断裂带附近发育的构造裂缝为漏失提供了通道,距离F I7断裂越近越易出现漏失,且漏失量越大。研究成果为PT1井区钻井过程井下复杂预防和处理提供了科学支撑。

穿断层破碎带隧道围岩大变形控制双梯度注浆机制

近些年,中国西部大量深埋隧道工程因关键线路控制无法避让一些活动性断裂,常常在跨越断裂带范围内出现围岩大变形破坏现象,例如侵限、偏压、塌方、底鼓等灾害,严重影响隧道工程施工和运营的安全可持续发展。为了控制断层破碎带隧道围岩大变形,隧道工程设计者和建设者采用了多种控制方案,例如超前注浆、多层钢拱架被动支护、锚杆索主动支护等,但是都因断层破碎带围岩强度过低而出现超前注浆诱发围岩拉裂破碎、主动支护锚杆锚固力不足等现象。为解决上述难题,首先,提出一种增强穿断层破碎带隧道围岩强度的双梯度注浆技术,建立双梯度注浆概念模型,构建3种双梯度注浆模式;然后,确定特定工况下注浆材料粒径梯度与注浆压力梯度的适配条件;最后,通过理论分析、物理模型试验和现场试验,探索双梯度注浆机制及其控制效果。研究结果表明:1)随着开挖步序的增加,穿断层破碎带隧道拱肩变形最大,构造应力对围岩稳定性影响较大。2)在双梯度注浆作用下,浆液扩散效果良好,围岩未出现大面积脱落破坏,隧道周围岩体应力分布均匀。3)双梯度注浆形成了坚硬交叉浆脉骨架,达到了应力补偿效果,将围岩变形量从原来的3 100 mm控制到278 mm以内,实现了“零换拱、零侵限、零突涌”的目标。

鲁中南典型地热区地热水氟分布特征及其驱动机制

山东省鲁中南典型地热区主要包括沂沭断裂带地热区和鲁中隆起地热区,为了探明研究区地热水氟分布特征及其富集规律,综合运用水化学图解、地球化学模拟和主成分分析等方法,分析沂沭断裂带地热区和鲁中隆起地热区地热水水化学数据。结果表明:研究区地热水以Na-Ca-Cl型、Na-Ca-SO_(4)-Cl型和Na-Cl^(-)SO 4型为主,基本为弱碱性水,优势阳离子为Na^(+),氟质量浓度在0.38~4.5 mg/L之间,富钠弱碱性环境有利于地热水中氟的富集。地热水中F-质量浓度与Na^(+)、Cl^(-)和总溶解固体(TDS)质量浓度呈显著正相关,而沂沭断裂带地热水样中F-质量浓度还与K^(+)、SO_(4)^(2-)质量浓度呈显著正相关,与Mg^(2+)和HCO_(3)质量浓度呈显著负相关;鲁中隆起地热区地热水中阳离子交换作用较沂沭断裂带地热区更为强烈,Na^(+)反应强度明显强于Mg^(2+)。鲁中隆起地热区和沂沭断裂带地热区均为裂隙型热储,热储岩性分别为石灰岩、灰岩热蚀变带和安山岩破碎带,水岩作用强烈。研究区地热水中氟离子的物质来源主要为萤石等含氟矿物的溶解沉淀,受控于阳离子交换等水岩相互作用影响,最终形成高氟地热水,其中高温和富钠对研究区地热水中氟离子富集影响较大。研究成果为地热资源开发利用提供了参考。

鄂尔多斯盆地西南缘延长组断缝体特征及对油藏的调控作用

鄂尔多斯盆地西南缘断缝体发育,针对断缝体对延长组油藏甜点分布控制作用的研究有待深化。利用大量的地震及测井解释结果,从断缝体演化机制角度对断缝体特征进行精细描述,进而系统探讨断缝体对油气的调控作用。研究结果表明,鄂尔多斯盆地西南缘发育直立走滑断裂,多具有“Y”字型、花状及负花状结构,且断裂常穿过白垩系底、延安组底、长7油层组底等界面,向下则插入基底。部分断裂仍具有早期逆断性质,表明断裂在后期反转程度不彻底。主断裂在不同部位具有不同的形态及偏移量,剖面上表现为张扭及压扭性质的循环转变,平面上则表现为不同类型断裂组合形式的交替出现。构建了断缝体中走滑断裂的发育模式,走滑断裂具有典型的多期活动、继承发育的特征。长8油层组主要发育垂直缝及水平层理缝,水平层理缝的发育频率为62.5%,垂直缝的发育频率为37.5%,且垂直缝含油级别相对较高。裂缝主要发育于分流河道细砂岩。当距主断裂距离大于1.25~1.5 km时,裂缝发育程度急剧降低,存在断缝体边界;在该边界范围内,厚度小于6 m的单砂体裂缝较为发育,当单砂体厚度超过6m,裂缝发育程度急剧降低。所构建的基于沉积(基础)、构造(主导)及裂缝(见效)的指标体系可以有效预测研究区长8油层组断缝体油藏有利区。

渗流-应力耦合作用下穿断层破碎带TBM输水隧洞结构安全研究

为分析敞开式隧道掘进机(TBM)穿越断层破碎带深埋长输水隧洞围岩的稳定性及其支护结构的安全性,依托东庄水利枢纽北线输水隧洞工程,采用ABAQUS软件建立隧洞开挖过程渗流-应力耦合三维动态施工仿真模型,研究了隧洞开挖支护过程中断层破碎带处围岩的稳定性和支护结构的受力特性及其变化规律。结果表明:隧洞围岩由于卸载作用其孔隙度最大值较初始状态增大了0.88%,渗透系数最大值较初始状态增大了2.59%;隧洞围岩孔隙水压力随开挖支护过程先下降—再平缓—最后回升至稳定;围岩塑性区出现在沿径向1 m范围内,等效塑性应变极值出现在围岩腰线处;锚杆应力在衬砌进行支护时达到峰值,其最大值为182.90 MPa;衬砌内、外缘均处于受压状态,衬砌环向应力值随开挖支护过程先出现最大值,随后略微减小至稳定,其值在6.66~11.92 MPa范围内;衬砌的变形整体上表现为向内收缩,收缩量从顶拱和底拱处向腰线处逐渐减小,其值在0.67~1.35 mm范围内;随着排水量的增加,围岩最大径缩量逐渐增大,衬砌外水压力折减系数逐渐减小。研究结果可为穿断层破碎带TBM隧洞工程结构设计及其安全施工和运营提供参考依据。

天山胜利隧道敞开式TBM钢管片支护作用效果研究

针对TBM穿越断层破碎带地层洞壁围岩松动掉块严重的问题,依托乌尉天山胜利隧道,采用数值模拟的方法,通过对比研究传统支护方式与新型钢管片支护方式下围岩变形和围岩塑性区情况,研究钢管片支护的作用效果;同时,为说明不同支护的适用条件,采用现场调研方法开展不同支护方式下施工效率和经济性对比分析。结果表明:1)断层破碎带地层中,当围岩出露护盾后,变形量与塑性区范围增大,围岩破坏程度加剧,以锚杆和钢拱架为主的传统支护方式无法较好地控制围岩变形和塑性区发展。2)断层破碎带地层中,钢管片支护较传统支护的围岩累计沉降值降低53%,围岩变形收敛快,能更好地控制围岩变形和发展。3)钢管片支护较传统支护的围岩塑性区范围小,其中边墙的最终塑性区缩小44%,且钢管片支护可实现早封闭、及时支护,塑性区均匀,更有利于围岩的稳定。4)一般地层中,传统支护方式的经济性和效率更佳;断层破碎带地层中,钢管片支护方式可提供安全作业空间,减小钢拱架+喷锚支护作业量,较传统支护经济性和施工效率更佳。

甘肃舟曲江顶崖古滑坡形成演化机理与堆积体稳定性评价

古滑坡堆积体复活是我国青藏高原及周边地区的主要地质灾害类型之一,也是我国西部正在建设的重大交通和水利工程面临的主要安全威胁之一。因此,对古滑坡的形成演化机理进行研究并对其堆积体进行稳定性评价,显得极为重要,可以为古滑坡堆积体复活的早期识别与防治设计提供理论支持。甘肃省舟曲县江顶崖古滑坡堆积体近十年来数次局部复活形成滑坡堵塞白龙江,对当地人民的生命财产安全造成严重威胁。通过现场调查和无人机倾斜摄影等手段,查明了江顶崖古滑坡堆积体的形态和结构特征,在此基础上分析了滑坡的演化机理和动力学过程,再结合InSAR变形数据对堆积体的稳定性进行了定性评价。结果显示,江顶崖古滑坡是典型的大型地震滑坡,其滑体沿3个方向坐落式下滑,形成了如今多级台阶状的堆积体形态;在地震荷载作用下古滑坡的动力学过程可分为中上部震动-拉裂、前缘锁固段剪断-滑坡启动、后缘拉裂-滑体加速、前缘受阻-滑体减速、稳定阶段。由于古滑坡在地震荷载作用下整体下滑,导致上部堆积体内存在大量结构完整的岩体,因此较为稳定;而中下部堆积体大都为断层破碎带和破碎岩体组成的软弱结构,稳定性较差,未来极有可能复活。

强富水区山岭隧道穿越断层破碎带施工技术研究

为降低隧道穿越断层破碎带施工中的涌水突泥风险,该文依托古兜山隧道实体工程,采用“TSP+地质雷达+超前地质钻孔”的地质超前预报技术,探明隧道掌子面前方的地层状况和富水程度,提出富水区隧道穿越断层破碎带施工关键技术。提出隧道洞口明挖法与隧道洞内光面爆破技术及洞内围岩段的双侧壁导坑法、单侧壁导坑法、三台阶七部法的开挖方式;采用S-Ⅴb型隧道衬砌结构型式与全断面帷幕注浆、加强泄水等技术相结合的支护方式,其中的整体承载结构为初期支撑系统和二次模筑衬砌的组合结构。该施工关键技术可有效避免古兜山隧道施工的突水涌泥现象,可指导类似工程的施工。

高地应力断层破碎带隧道变形及受力特征研究

针对隧道在穿越高地应力断层破碎带时,易引发围岩大变形、混凝土开裂和拱架变形等破坏问题,依托象君山隧道工程,通过现场试验,分析了断层破碎带及附近不同等级围岩断面开挖引起的隧道变形和受力特征。研究表明:在下台阶开挖前,隧道拱顶沉降和上台阶收敛均达到峰值的70%,断层破碎带处收敛变形呈现明显的“上大下小”现象,而在断层破碎带附近的断面沉降则呈现出明显对称现象;隧道断层破碎带的最大沉降值为73.4mm,在隧道拱顶处,并且观察到喷射混凝土局部开裂和钢架扭曲,在后续施工中建议采用“先柔后刚”的双层初支方案;围岩压力在空间上呈现离散分布,在断层破碎带及其附近断面的围岩压力都是非对称分布,在拱脚和边墙处并未出现较大拉应力区,且拱部受力明显大于拱顶,说明水平构造应力明显;断层破碎带隧道围岩变形和初支受力特征主要是由区域构造应力、最大主应力和岩体综合结构决定,断层破碎带围岩变形和初支受力情况在一定程度上反映了围岩初期变形情况。